1 ==================================================
2 A Record of reStructuredText Syntax Alternatives
3 ==================================================
6 :Contact: docutils-develop@lists.sourceforge.net
9 :Copyright: This document has been placed in the public domain.
11 The following are ideas, alternatives, and justifications that were
12 considered for reStructuredText syntax, which did not originate with
13 Setext_ or StructuredText_. For an analysis of constructs which *did*
14 originate with StructuredText or Setext, please see `Problems With
15 StructuredText`_. See the `reStructuredText Markup Specification`_
16 for full details of the established syntax.
18 The ideas are divided into sections:
20 * Implemented_: already done. The issues and alternatives are
21 recorded here for posterity.
23 * `Not Implemented`_: these ideas won't be implemented.
25 * Tabled_: these ideas should be revisited in the future.
27 * `To Do`_: these ideas should be implemented. They're just waiting
28 for a champion to resolve issues and get them done.
30 * `... Or Not To Do?`_: possible but questionable. These probably
31 won't be implemented, but you never know.
33 .. _Setext: http://docutils.sourceforge.net/mirror/setext.html
35 http://www.zope.org/DevHome/Members/jim/StructuredTextWiki/FrontPage
36 .. _Problems with StructuredText: problems.html
37 .. _reStructuredText Markup Specification:
38 ../../ref/rst/restructuredtext.html
50 Prior to the syntax for field lists being finalized, several
51 alternatives were proposed.
53 1. Unadorned RFC822_ everywhere::
58 Advantages: clean, precedent (RFC822-compliant). Disadvantage:
59 ambiguous (these paragraphs are a prime example).
63 2. Special case: use unadorned RFC822_ for the very first or very last
64 text block of a document::
70 The rest of the document...
73 Advantages: clean, precedent (RFC822-compliant). Disadvantages:
74 special case, flat (unnested) field lists only, still ambiguous::
77 Usage: cmdname [options] arg1 arg2 ...
79 We obviously *don't* want the like above to be interpreted as a
80 field list item. Or do we?
83 Conclusion: rejected for the general case, accepted for specific
84 contexts (PEPs, email).
93 Advantages: explicit and unambiguous, RFC822-compliant.
94 Disadvantage: cumbersome.
96 Conclusion: rejected for the general case (but such a directive
97 could certainly be written).
99 4. Use Javadoc-style::
105 Advantages: unambiguous, precedent, flexible. Disadvantages:
106 non-intuitive, ugly, not RFC822-compliant.
108 Conclusion: rejected.
110 5. Use leading colons::
115 Advantages: unambiguous, obvious (*almost* RFC822-compliant),
116 flexible, perhaps even elegant. Disadvantages: no precedent, not
117 quite RFC822-compliant.
119 Conclusion: accepted!
121 6. Use double colons::
126 Advantages: unambiguous, obvious? (*almost* RFC822-compliant),
127 flexible, similar to syntax already used for literal blocks and
128 directives. Disadvantages: no precedent, not quite
129 RFC822-compliant, similar to syntax already used for literal blocks
132 Conclusion: rejected because of the syntax similarity & conflicts.
134 Why is RFC822 compliance important? It's a universal Internet
135 standard, and super obvious. Also, I'd like to support the PEP format
136 (ulterior motive: get PEPs to use reStructuredText as their standard).
137 But it *would* be easy to get used to an alternative (easy even to
138 convert PEPs; probably harder to convert python-deviants ;-).
140 Unfortunately, without well-defined context (such as in email headers:
141 RFC822 only applies before any blank lines), the RFC822 format is
142 ambiguous. It is very common in ordinary text. To implement field
143 lists unambiguously, we need explicit syntax.
145 The following question was posed in a footnote:
147 Should "bibliographic field lists" be defined at the parser level,
148 or at the DPS transformation level? In other words, are they
149 reStructuredText-specific, or would they also be applicable to
150 another (many/every other?) syntax?
152 The answer is that bibliographic fields are a
153 reStructuredText-specific markup convention. Other syntaxes may
154 implement the bibliographic elements explicitly. For example, there
155 would be no need for such a transformation for an XML-based markup
158 .. _RFC822: http://www.rfc-editor.org/rfc/rfc822.txt
161 Interpreted Text "Roles"
162 ========================
164 The original purpose of interpreted text was as a mechanism for
165 descriptive markup, to describe the nature or role of a word or
166 phrase. For example, in XML we could say "<function>len</function>"
167 to mark up "len" as a function. It is envisaged that within Python
168 docstrings (inline documentation in Python module source files, the
169 primary market for reStructuredText) the role of a piece of
170 interpreted text can be inferred implicitly from the context of the
171 docstring within the program source. For other applications, however,
172 the role may have to be indicated explicitly.
174 Interpreted text is enclosed in single backquotes (`).
176 1. Initially, it was proposed that an explicit role could be indicated
177 as a word or phrase within the enclosing backquotes:
179 - As a prefix, separated by a colon and whitespace::
181 `role: interpreted text`
183 - As a suffix, separated by whitespace and a colon::
185 `interpreted text :role`
187 There are problems with the initial approach:
189 - There could be ambiguity with interpreted text containing colons.
190 For example, an index entry of "Mission: Impossible" would
191 require a backslash-escaped colon.
193 - The explicit role is descriptive markup, not content, and will
194 not be visible in the processed output. Putting it inside the
195 backquotes doesn't feel right; the *role* isn't being quoted.
197 2. Tony Ibbs suggested that the role be placed outside the
200 role:`prefix` or `suffix`:role
202 This removes the embedded-colons ambiguity, but limits the role
203 identifier to be a single word (whitespace would be illegal).
204 Since roles are not meant to be visible after processing, the lack
205 of whitespace support is not important.
207 The suggested syntax remains ambiguous with respect to ratios and
208 some writing styles. For example, suppose there is a "signal"
209 identifier, and we write::
211 ...calculate the `signal`:noise ratio.
213 "noise" looks like a role.
215 3. As an improvement on #2, we can bracket the role with colons::
217 :role:`prefix` or `suffix`:role:
219 This syntax is similar to that of field lists, which is fine since
220 both are doing similar things: describing.
222 This is the syntax chosen for reStructuredText.
224 4. Another alternative is two colons instead of one::
226 role::`prefix` or `suffix`::role
228 But this is used for analogies ("A:B::C:D": "A is to B as C is to
231 Both alternative #2 and #4 lack delimiters on both sides of the
232 role, making it difficult to parse (by the reader).
234 5. Some kind of bracketing could be used:
238 (role)`prefix` or `suffix`(role)
242 {role}`prefix` or `suffix`{role}
246 [role]`prefix` or `suffix`[role]
250 <role>`prefix` or `suffix`<role>
252 (The overlap of \*ML tags with angle brackets would be too
253 confusing and precludes their use.)
255 Syntax #3 was chosen for reStructuredText.
261 A problem with comments (actually, with all indented constructs) is
262 that they cannot be followed by an indented block -- a block quote --
263 without swallowing it up.
265 I thought that perhaps comments should be one-liners only. But would
266 this mean that footnotes, hyperlink targets, and directives must then
267 also be one-liners? Not a good solution.
269 Tony Ibbs suggested a "comment" directive. I added that we could
270 limit a comment to a single text block, and that a "multi-block
271 comment" could use "comment-start" and "comment-end" directives. This
272 would remove the indentation incompatibility. A "comment" directive
273 automatically suggests "footnote" and (hyperlink) "target" directives
274 as well. This could go on forever! Bad choice.
276 Garth Kidd suggested that an "empty comment", a ".." explicit markup
277 start with nothing on the first line (except possibly whitespace) and
278 a blank line immediately following, could serve as an "unindent". An
279 empty comment does **not** swallow up indented blocks following it,
280 so block quotes are safe. "A tiny but practical wart." Accepted.
286 Alan Jaffray came up with this idea, along with the following syntax::
288 Search the `Python DOC-SIG mailing list archives`{}_.
290 .. _: http://mail.python.org/pipermail/doc-sig/
292 The idea is sound and useful. I suggested a "double underscore"
295 Search the `Python DOC-SIG mailing list archives`__.
297 .. __: http://mail.python.org/pipermail/doc-sig/
299 But perhaps single underscores are okay? The syntax looks better, but
300 the hyperlink itself doesn't explicitly say "anonymous"::
302 Search the `Python DOC-SIG mailing list archives`_.
304 .. _: http://mail.python.org/pipermail/doc-sig/
306 Mixing anonymous and named hyperlinks becomes confusing. The order of
307 targets is not significant for named hyperlinks, but it is for
308 anonymous hyperlinks::
310 Hyperlinks: anonymous_, named_, and another anonymous_.
316 Without the extra syntax of double underscores, determining which
317 hyperlink references are anonymous may be difficult. We'd have to
318 check which references don't have corresponding targets, and match
319 those up with anonymous targets. Keeping to a simple consistent
320 ordering (as with auto-numbered footnotes) seems simplest.
322 reStructuredText will use the explicit double-underscore syntax for
323 anonymous hyperlinks. An alternative (see `Reworking Explicit Markup
324 (Round 1)`_ below) for the somewhat awkward ".. __:" syntax is "__"::
326 An anonymous__ reference.
331 Reworking Explicit Markup (Round 1)
332 ===================================
334 Alan Jaffray came up with the idea of `anonymous hyperlinks`_, added
335 to reStructuredText. Subsequently it was asserted that hyperlinks
336 (especially anonymous hyperlinks) would play an increasingly important
337 role in reStructuredText documents, and therefore they require a
338 simpler and more concise syntax. This prompted a review of the
339 current and proposed explicit markup syntaxes with regards to
344 .. _blah: internal hyperlink target
345 .. _blah: http://somewhere external hyperlink target
346 .. _blah: blahblah_ indirect hyperlink target
347 .. __: anonymous internal target
348 .. __: http://somewhere anonymous external target
349 .. __: blahblah_ anonymous indirect target
350 .. [blah] http://somewhere footnote
351 .. blah:: http://somewhere directive
352 .. blah: http://somewhere comment
356 The comment text was intentionally made to look like a hyperlink
361 * Except for the colon (a delimiter necessary to allow for
362 phrase-links), hyperlink target ``.. _blah:`` comes from Setext.
363 * Comment syntax from Setext.
364 * Footnote syntax from StructuredText ("named links").
365 * Directives and anonymous hyperlinks original to reStructuredText.
369 + Consistent explicit markup indicator: "..".
370 + Consistent hyperlink syntax: ".. _" & ":".
374 - Anonymous target markup is awkward: ".. __:".
375 - The explicit markup indicator ("..") is excessively overloaded?
376 - Comment text is limited (can't look like a footnote, hyperlink,
377 or directive). But this is probably not important.
379 2. Alan Jaffray's proposed syntax #1::
381 __ _blah internal hyperlink target
382 __ blah: http://somewhere external hyperlink target
383 __ blah: blahblah_ indirect hyperlink target
384 __ anonymous internal target
385 __ http://somewhere anonymous external target
386 __ blahblah_ anonymous indirect target
387 __ [blah] http://somewhere footnote
388 .. blah:: http://somewhere directive
389 .. blah: http://somewhere comment
391 The hyperlink-connoted underscores have become first-level syntax.
395 + Anonymous targets are simpler.
396 + All hyperlink targets are one character shorter.
400 - Inconsistent internal hyperlink targets. Unlike all other named
401 hyperlink targets, there's no colon. There's an extra leading
402 underscore, but we can't drop it because without it, "blah" looks
403 like a relative URI. Unless we restore the colon::
405 __ blah: internal hyperlink target
409 3. Alan Jaffray's proposed syntax #2::
411 .. _blah internal hyperlink target
412 .. blah: http://somewhere external hyperlink target
413 .. blah: blahblah_ indirect hyperlink target
414 .. anonymous internal target
415 .. http://somewhere anonymous external target
416 .. blahblah_ anonymous indirect target
417 .. [blah] http://somewhere footnote
418 !! blah: http://somewhere directive
419 ## blah: http://somewhere comment
421 Leading underscores have been (almost) replaced by "..", while
422 comments and directives have gained their own syntax.
426 + Anonymous hyperlinks are simpler.
427 + Unique syntax for comments. Connotation of "comment" from
428 some programming languages (including our favorite).
429 + Unique syntax for directives. Connotation of "action!".
433 - Inconsistent internal hyperlink targets. Again, unlike all other
434 named hyperlink targets, there's no colon. There's a leading
435 underscore, matching the trailing underscores of references,
436 which no other hyperlink targets have. We can't drop that one
437 leading underscore though: without it, "blah" looks like a
438 relative URI. Again, unless we restore the colon::
440 .. blah: internal hyperlink target
442 - All (except for internal) hyperlink targets lack their leading
443 underscores, losing the "hyperlink" connotation.
445 - Obtrusive syntax for comments. Alternatives::
447 ;; blah: http://somewhere
448 (also comment syntax in Lisp & others)
449 ,, blah: http://somewhere
450 ("comma comma": sounds like "comment"!)
452 - Iffy syntax for directives. Alternatives?
454 4. Tony Ibbs' proposed syntax::
456 .. _blah: internal hyperlink target
457 .. _blah: http://somewhere external hyperlink target
458 .. _blah: blahblah_ indirect hyperlink target
459 .. anonymous internal target
460 .. http://somewhere anonymous external target
461 .. blahblah_ anonymous indirect target
462 .. [blah] http://somewhere footnote
463 .. blah:: http://somewhere directive
464 .. blah: http://somewhere comment
466 This is the same as the current syntax, except for anonymous
467 targets which drop their "__: ".
471 + Anonymous targets are simpler.
475 - Anonymous targets lack their leading underscores, losing the
476 "hyperlink" connotation.
477 - Anonymous targets are almost indistinguishable from comments.
478 (Better to know "up front".)
480 5. David Goodger's proposed syntax: Perhaps going back to one of
481 Alan's earlier suggestions might be the best solution. How about
482 simply adding "__ " as a synonym for ".. __: " in the original
483 syntax? These would become equivalent::
485 .. __: anonymous internal target
486 .. __: http://somewhere anonymous external target
487 .. __: blahblah_ anonymous indirect target
489 __ anonymous internal target
490 __ http://somewhere anonymous external target
491 __ blahblah_ anonymous indirect target
493 Alternative 5 has been adopted.
496 Backquotes in Phrase-Links
497 ==========================
499 [From a 2001-06-05 Doc-SIG post in reply to questions from Doug
502 The first draft of the spec, posted to the Doc-SIG in November 2000,
503 used square brackets for phrase-links. I changed my mind because:
505 1. In the first draft, I had already decided on single-backquotes for
508 2. However, I wanted to minimize the necessity for backslash escapes,
509 for example when quoting Python repr-equivalent syntax that uses
512 3. The processing of identifiers (function/method/attribute/module
513 etc. names) into hyperlinks is a useful feature. PyDoc recognizes
514 identifiers heuristically, but it doesn't take much imagination to
515 come up with counter-examples where PyDoc's heuristics would result
516 in embarrassing failure. I wanted to do it deterministically, and
517 that called for syntax. I called this construct "interpreted
520 4. Leveraging off the ``*emphasis*/**strong**`` syntax, lead to the
521 idea of using double-backquotes as syntax.
523 5. I worked out some rules for inline markup recognition.
525 6. In combination with #5, double backquotes lent themselves to inline
526 literals, neatly satisfying #2, minimizing backslash escapes. In
527 fact, the spec says that no interpretation of any kind is done
528 within double-backquote inline literal text; backslashes do *no*
529 escaping within literal text.
531 7. Single backquotes are then freed up for interpreted text.
533 8. I already had square brackets required for footnote references.
535 9. Since interpreted text will typically turn into hyperlinks, it was
536 a natural fit to use backquotes as the phrase-quoting syntax for
537 trailing-underscore hyperlinks.
539 The original inspiration for the trailing underscore hyperlink syntax
540 was Setext. But for phrases Setext used a very cumbersome
541 ``underscores_between_words_like_this_`` syntax.
543 The underscores can be viewed as if they were right-pointing arrows:
544 ``-->``. So ``hyperlink_`` points away from the reference, and
545 ``.. _hyperlink:`` points toward the target.
548 Substitution Mechanism
549 ======================
551 Substitutions arose out of a Doc-SIG thread begun on 2001-10-28 by
552 Alan Jaffray, "reStructuredText inline markup". It reminded me of a
553 missing piece of the reStructuredText puzzle, first referred to in my
554 contribution to "Documentation markup & processing / PEPs" (Doc-SIG
557 Substitutions allow the power and flexibility of directives to be
558 shared by inline text. They are a way to allow arbitrarily complex
559 inline objects, while keeping the details out of the flow of text.
560 They are the equivalent of SGML/XML's named entities. For example, an
561 inline image (using reference syntax alternative 4d (vertical bars)
562 and definition alternative 3, the alternatives chosen for inclusion in
565 The |biohazard| symbol must be used on containers used to dispose
568 .. |biohazard| image:: biohazard.png
571 The ``|biohazard|`` substitution reference will be replaced in-line by
572 whatever the ``.. |biohazard|`` substitution definition generates (in
573 this case, an image). A substitution definition contains the
574 substitution text bracketed with vertical bars, followed by a an
575 embedded inline-compatible directive, such as "image". A transform is
576 required to complete the substitution.
578 Syntax alternatives for the reference:
580 1. Use the existing interpreted text syntax, with a predefined role
583 The `biohazard`:sub: symbol...
585 Advantages: existing syntax, explicit. Disadvantages: verbose,
588 2. Use a variant of the interpreted text syntax, with a new suffix
589 akin to the underscore in phrase-link references::
600 Due to incompatibility with other constructs and ordinary text
601 usage, (f) and (g) are not possible.
603 3. Use interpreted text syntax with a fixed internal format::
619 To avoid ML confusion (k) and (l) are definitely out. Square
620 brackets (j) won't work in the target (the substitution definition
621 would be indistinguishable from a footnote).
623 The ```/name/``` syntax (g) is reminiscent of "s/find/sub"
624 substitution syntax in ed-like languages. However, it may have a
625 misleading association with regexps, and looks like an absolute
626 POSIX path. (i) is visually equivalent and lacking the
629 A disadvantage of all of these is that they limit interpreted text,
630 albeit only slightly.
632 4. Use specialized syntax, something new::
649 "#" (a) and "@" (b) are obtrusive. "/" (c) without backquotes
650 looks just like a POSIX path; it is likely for such usage to appear
653 "|" (d) and "^" (h) are feasible.
655 5. Redefine the trailing underscore syntax. See definition syntax
656 alternative 4, below.
658 Syntax alternatives for the definition:
660 1. Use the existing directive syntax, with a predefined directive such
661 as "sub". It contains a further embedded directive resolving to an
662 inline-compatible object::
665 .. image:: biohazard.png
669 That bird wouldn't *voom* if you put 10,000,000 volts
672 The advantages and disadvantages are the same as in inline
675 2. Use syntax as in #1, but with an embedded directivecompressed::
677 .. sub:: biohazard image:: biohazard.png
680 This is a bit better than alternative 1, but still too much.
682 3. Use a variant of directive syntax, incorporating the substitution
683 text, obviating the need for a special "sub" directive name. If we
684 assume reference alternative 4d (vertical bars), the matching
685 definition would look like this::
687 .. |biohazard| image:: biohazard.png
690 4. (Suggested by Alan Jaffray on Doc-SIG from 2001-11-06.)
692 Instead of adding new syntax, redefine the trailing underscore
693 syntax to mean "substitution reference" instead of "hyperlink
694 reference". Alan's example::
696 I had lunch with Jonathan_ today. We talked about Zope_.
698 .. _Jonathan: lj [user=jhl]
699 .. _Zope: http://www.zope.org/
701 A problem with the proposed syntax is that URIs which look like
702 simple reference names (alphanum plus ".", "-", "_") would be
703 indistinguishable from substitution directive names. A more
704 consistent syntax would be::
706 I had lunch with Jonathan_ today. We talked about Zope_.
708 .. _Jonathan: lj:: user=jhl
709 .. _Zope: http://www.zope.org/
711 (``::`` after ``.. _Jonathan: lj``.)
713 The "Zope" target is a simple external hyperlink, but the
714 "Jonathan" target contains a directive. Alan proposed is that the
715 reference text be replaced by whatever the referenced directive
716 (the "directive target") produces. A directive reference becomes a
717 hyperlink reference if the contents of the directive target resolve
718 to a hyperlink. If the directive target resolves to an icon, the
719 reference is replaced by an inline icon. If the directive target
720 resolves to a hyperlink, the directive reference becomes a
723 This seems too indirect and complicated for easy comprehension.
725 The reference in the text will sometimes become a link, sometimes
726 not. Sometimes the reference text will remain, sometimes not. We
727 don't know *at the reference*::
729 This is a `hyperlink reference`_; its text will remain.
730 This is an `inline icon`_; its text will disappear.
734 The syntax that has been incorporated into the spec and parser is
735 reference alternative 4d with definition alternative 3::
737 The |biohazard| symbol...
739 .. |biohazard| image:: biohazard.png
742 We can also combine substitution references with hyperlink references,
743 by appending a "_" (named hyperlink reference) or "__" (anonymous
744 hyperlink reference) suffix to the substitution reference. This
745 allows us to click on an image-link::
747 The |biohazard|_ symbol...
749 .. |biohazard| image:: biohazard.png
751 .. _biohazard: http://www.cdc.gov/
753 There have been several suggestions for the naming of these
754 constructs, originally called "substitution references" and
757 1. Candidate names for the reference construct:
759 (a) substitution reference
760 (b) tagging reference
761 (c) inline directive reference
762 (d) directive reference
763 (e) indirect inline directive reference
764 (f) inline directive placeholder
765 (g) inline directive insertion reference
766 (h) directive insertion reference
767 (i) insertion reference
768 (j) directive macro reference
770 (l) substitution directive reference
772 2. Candidate names for the definition construct:
775 (b) substitution directive
780 (g) inline directive definition
781 (h) referenced directive
782 (i) indirect directive
783 (j) indirect directive definition
784 (k) directive definition
785 (l) indirect inline directive
786 (m) named directive definition
787 (n) inline directive insertion definition
788 (o) directive insertion definition
789 (p) insertion definition
790 (q) insertion directive
791 (r) substitution definition
792 (s) directive macro definition
794 (u) substitution directive definition
795 (v) substitution definition
797 "Inline directive reference" (1c) seems to be an appropriate term at
798 first, but the term "inline" is redundant in the case of the
799 reference. Its counterpart "inline directive definition" (2g) is
800 awkward, because the directive definition itself is not inline.
802 "Directive reference" (1d) and "directive definition" (2k) are too
803 vague. "Directive definition" could be used to refer to any
804 directive, not just those used for inline substitutions.
806 One meaning of the term "macro" (1k, 2s, 2t) is too
807 programming-language-specific. Also, macros are typically simple text
808 substitution mechanisms: the text is substituted first and evaluated
809 later. reStructuredText substitution definitions are evaluated in
810 place at parse time and substituted afterwards.
812 "Insertion" (1h, 1i, 2n-2q) is almost right, but it implies that
813 something new is getting added rather than one construct being
816 Which brings us back to "substitution". The overall best names are
817 "substitution reference" (1a) and "substitution definition" (2v). A
818 long way to go to add one word!
821 Inline External Targets
822 =======================
824 Currently reStructuredText has two hyperlink syntax variations:
828 This is a named reference_ of one word ("reference"). Here is
829 a `phrase reference`_. Phrase references may even cross `line
832 .. _reference: http://www.example.org/reference/
833 .. _phrase reference: http://www.example.org/phrase_reference/
834 .. _line boundaries: http://www.example.org/line_boundaries/
838 - The plaintext is readable.
839 - Each target may be reused multiple times (e.g., just write
840 ``"reference_"`` again).
841 - No syncronized ordering of references and targets is necessary.
845 - The reference text must be repeated as target names; could lead
847 - The target URLs may be located far from the references, and hard
848 to find in the plaintext.
850 * Anonymous hyperlinks (in current reStructuredText)::
852 This is an anonymous reference__. Here is an anonymous
853 `phrase reference`__. Phrase references may even cross `line
856 __ http://www.example.org/reference/
857 __ http://www.example.org/phrase_reference/
858 __ http://www.example.org/line_boundaries/
862 - The plaintext is readable.
863 - The reference text does not have to be repeated.
867 - References and targets must be kept in sync.
868 - Targets cannot be reused.
869 - The target URLs may be located far from the references.
871 For comparison and historical background, StructuredText also has two
872 syntaxes for hyperlinks:
874 * First, ``"reference text":URL``::
876 This is a "reference":http://www.example.org/reference/
877 of one word ("reference"). Here is a "phrase
878 reference":http://www.example.org/phrase_reference/.
880 * Second, ``"reference text", http://example.com/absolute_URL``::
882 This is a "reference", http://www.example.org/reference/
883 of one word ("reference"). Here is a "phrase reference",
884 http://www.example.org/phrase_reference/.
886 Both syntaxes share advantages and disadvantages:
890 - The target is specified immediately adjacent to the reference.
894 - Poor plaintext readability.
895 - Targets cannot be reused.
896 - Both syntaxes use double quotes, common in ordinary text.
897 - In the first syntax, the URL and the last word are stuck
898 together, exacerbating the line wrap problem.
899 - The second syntax is too magical; text could easily be written
900 that way by accident (although only absolute URLs are recognized
901 here, perhaps because of the potential for ambiguity).
903 A new type of "inline external hyperlink" has been proposed.
905 1. On 2002-06-28, Simon Budig proposed__ a new syntax for
906 reStructuredText hyperlinks::
908 This is a reference_(http://www.example.org/reference/) of one
909 word ("reference"). Here is a `phrase
910 reference`_(http://www.example.org/phrase_reference/). Are
911 these examples, (single-underscore), named? If so, `anonymous
912 references`__(http://www.example.org/anonymous/) using two
913 underscores would probably be preferable.
915 __ http://mail.python.org/pipermail/doc-sig/2002-June/002648.html
917 The syntax, advantages, and disadvantages are similar to those of
922 - The target is specified immediately adjacent to the reference.
926 - Poor plaintext readability.
927 - Targets cannot be reused (unless named, but the semantics are
932 - The ``"`ref`_(URL)"`` syntax forces the last word of the
933 reference text to be joined to the URL, making a potentially
934 very long word that can't be wrapped (URLs can be very long).
935 The reference and the URL should be separate. This is a
936 symptom of the following point:
938 - The syntax produces a single compound construct made up of two
939 equally important parts, *with syntax in the middle*, *between*
940 the reference and the target. This is unprecedented in
943 - The "inline hyperlink" text is *not* a named reference (there's
944 no lookup by name), so it shouldn't look like one.
946 - According to the IETF standards RFC 2396 and RFC 2732,
947 parentheses are legal URI characters and curly braces are legal
948 email characters, making their use prohibitively difficult.
950 - The named/anonymous semantics are unclear.
952 2. After an analysis__ of the syntax of (1) above, we came up with the
953 following compromise syntax::
955 This is an anonymous reference__
956 __<http://www.example.org/reference/> of one word
957 ("reference"). Here is a `phrase reference`__
958 __<http://www.example.org/phrase_reference/>. `Named
959 references`_ _<http://www.example.org/anonymous/> use single
962 __ http://mail.python.org/pipermail/doc-sig/2002-July/002670.html
964 The syntax builds on that of the existing "inline internal
965 targets": ``an _`inline internal target`.``
969 - The target is specified immediately adjacent to the reference,
970 improving maintainability:
972 - References and targets are easily kept in sync.
973 - The reference text does not have to be repeated.
975 - The construct is executed in two parts: references identical to
976 existing references, and targets that are new but not too big a
977 stretch from current syntax.
979 - There's overwhelming precedent for quoting URLs with angle
984 - Poor plaintext readability.
985 - Lots of "line noise".
986 - Targets cannot be reused (unless named; see below).
988 To alleviate the readability issue slightly, we could allow the
989 target to appear later, such as after the end of the sentence::
991 This is a named reference__ of one word ("reference").
992 __<http://www.example.org/reference/> Here is a `phrase
993 reference`__. __<http://www.example.org/phrase_reference/>
995 Problem: this could only work for one reference at a time
996 (reference/target pairs must be proximate [refA trgA refB trgB],
997 not interleaved [refA refB trgA trgB] or nested [refA refB trgB
998 trgA]). This variation is too problematic; references and inline
999 external targets will have to be kept immediately adjacent (see (3)
1002 The ``"reference__ __<target>"`` syntax is actually for "anonymous
1003 inline external targets", emphasized by the double underscores. It
1004 follows that single trailing and leading underscores would lead to
1005 *implicitly named* inline external targets. This would allow the
1006 reuse of targets by name. So after ``"reference_ _<target>"``,
1007 another ``"reference_"`` would point to the same target.
1010 From RFC 2396 (URI syntax):
1012 The angle-bracket "<" and ">" and double-quote (")
1013 characters are excluded [from URIs] because they are often
1014 used as the delimiters around URI in text documents and
1017 Using <> angle brackets around each URI is especially
1018 recommended as a delimiting style for URI that contain
1021 From RFC 822 (email headers):
1023 Angle brackets ("<" and ">") are generally used to indicate
1024 the presence of a one machine-usable reference (e.g.,
1025 delimiting mailboxes), possibly including source-routing to
1028 3. If it is best for references and inline external targets to be
1029 immediately adjacent, then they might as well be integrated.
1030 Here's an alternative syntax embedding the target URL in the
1033 This is an anonymous `reference <http://www.example.org
1034 /reference/>`__ of one word ("reference"). Here is a `phrase
1035 reference <http://www.example.org/phrase_reference/>`__.
1037 Advantages and disadvantages are similar to those in (2).
1038 Readability is still an issue, but the syntax is a bit less
1039 heavyweight (reduced line noise). Backquotes are required, even
1040 for one-word references; the target URL is included within the
1041 reference text, forcing a phrase context.
1043 We'll call this variant "embedded URIs".
1045 Problem: how to refer to a title like "HTML Anchors: <a>" (which
1046 ends with an HTML/SGML/XML tag)? We could either require more
1047 syntax on the target (like ``"`reference text
1048 __<http://example.com/>`__"``), or require the odd conflicting
1049 title to be escaped (like ``"`HTML Anchors: \<a>`__"``). The
1050 latter seems preferable, and not too onerous.
1052 Similarly to (2) above, a single trailing underscore would convert
1053 the reference & inline external target from anonymous to implicitly
1054 named, allowing reuse of targets by name.
1056 I think this is the least objectionable of the syntax alternatives.
1058 Other syntax variations have been proposed (by Brett Cannon and Benja
1061 `phrase reference`->http://www.example.com
1063 `phrase reference`@http://www.example.com
1065 `phrase reference`__ ->http://www.example.com
1067 `phrase reference` [-> http://www.example.com]
1069 `phrase reference`__ [-> http://www.example.com]
1071 `phrase reference` <http://www.example.com>_
1073 None of these variations are clearly superior to #3 above. Some have
1074 problems that exclude their use.
1076 With any kind of inline external target syntax it comes down to the
1077 conflict between maintainability and plaintext readability. I don't
1078 see a major problem with reStructuredText's maintainability, and I
1079 don't want to sacrifice plaintext readability to "improve" it.
1081 The proponents of inline external targets want them for easily
1082 maintainable web pages. The arguments go something like this:
1084 - Named hyperlinks are difficult to maintain because the reference
1085 text is duplicated as the target name.
1087 To which I said, "So use anonymous hyperlinks."
1089 - Anonymous hyperlinks are difficult to maintain because the
1090 references and targets have to be kept in sync.
1092 "So keep the targets close to the references, grouped after each
1093 paragraph. Maintenance is trivial."
1095 - But targets grouped after paragraphs break the flow of text.
1097 "Surely less than URLs embedded in the text! And if the intent is
1098 to produce web pages, not readable plaintext, then who cares about
1101 Many participants have voiced their objections to the proposed syntax:
1103 Garth Kidd: "I strongly prefer the current way of doing it.
1104 Inline is spectactularly messy, IMHO."
1106 Tony Ibbs: "I vehemently agree... that the inline alternatives
1107 being suggested look messy - there are/were good reasons they've
1108 been taken out... I don't believe I would gain from the new
1111 Paul Moore: "I agree as well. The proposed syntax is far too
1112 punctuation-heavy, and any of the alternatives discussed are
1113 ambiguous or too subtle."
1115 Others have voiced their support:
1117 fantasai: "I agree with Simon. In many cases, though certainly
1118 not in all, I find parenthesizing the url in plain text flows
1119 better than relegating it to a footnote."
1121 Ken Manheimer: "I'd like to weigh in requesting some kind of easy,
1122 direct inline reference link."
1124 (Interesting that those *against* the proposal have been using
1125 reStructuredText for a while, and those *for* the proposal are either
1126 new to the list ["fantasai", background unknown] or longtime
1127 StructuredText users [Ken Manheimer].)
1129 I was initially ambivalent/against the proposed "inline external
1130 targets". I value reStructuredText's readability very highly, and
1131 although the proposed syntax offers convenience, I don't know if the
1132 convenience is worth the cost in ugliness. Does the proposed syntax
1133 compromise readability too much, or should the choice be left up to
1134 the author? Perhaps if the syntax is *allowed* but its use strongly
1135 *discouraged*, for aesthetic/readability reasons?
1137 After a great deal of thought and much input from users, I've decided
1138 that there are reasonable use cases for this construct. The
1139 documentation should strongly caution against its use in most
1140 situations, recommending independent block-level targets instead.
1141 Syntax #3 above ("embedded URIs") will be used.
1144 Doctree Representation of Transitions
1145 =====================================
1147 (Although not reStructuredText-specific, this section fits best in
1150 Having added the "horizontal rule" construct to the `reStructuredText
1151 Markup Specification`_, a decision had to be made as to how to reflect
1152 the construct in the implementation of the document tree. Given this
1164 The horizontal rule indicates a "transition" (in prose terms) or the
1165 start of a new "division". Before implementation, the parsed document
1169 <section names="document">
1174 -------- <--- error here
1178 There are several possibilities for the implementation:
1180 1. Implement horizontal rules as "divisions" or segments. A
1181 "division" is a title-less, non-hierarchical section. The first
1182 try at an implementation looked like this::
1185 <section names="document">
1194 But the two paragraphs are really at the same level; they shouldn't
1195 appear to be at different levels. There's really an invisible
1196 "first division". The horizontal rule splits the document body
1197 into two segments, which should be treated uniformly.
1199 2. Treating "divisions" uniformly brings us to the second
1203 <section names="document">
1213 With this change, documents and sections will directly contain
1214 divisions and sections, but not body elements. Only divisions will
1215 directly contain body elements. Even without a horizontal rule
1216 anywhere, the body elements of a document or section would be
1217 contained within a division element. This makes the document tree
1218 deeper. This is similar to the way HTML_ treats document contents:
1219 grouped within a ``<body>`` element.
1221 3. Implement them as "transitions", empty elements::
1224 <section names="document">
1233 A transition would be a "point element", not containing anything,
1234 only identifying a point within the document structure. This keeps
1235 the document tree flatter, but the idea of a "point element" like
1236 "transition" smells bad. A transition isn't a thing itself, it's
1237 the space between two divisions. However, transitions are a
1240 Solution 3 was chosen for incorporation into the document tree model.
1242 .. _HTML: http://www.w3.org/MarkUp/
1245 Syntax for Line Blocks
1246 ======================
1248 * An early idea: How about a literal-block-like prefix, perhaps
1249 "``;;``"? (It is, after all, a *semi-literal* literal block, no?)
1252 Take it away, Eric the Orchestra Leader! ;;
1254 A one, two, a one two three four
1256 Half a bee, philosophically,
1257 must, *ipso facto*, half not be.
1258 But half the bee has got to be,
1259 *vis a vis* its entity. D'you see?
1261 But can a bee be said to be
1262 or not to be an entire bee,
1263 when half the bee is not a bee,
1264 due to some ancient injury?
1270 * Another idea: in an ordinary paragraph, if the first line ends with
1271 a backslash (escaping the newline), interpret the entire paragraph
1272 as a verse block? For example::
1274 Add just one backslash\
1275 And this paragraph becomes
1278 (Awful, and arguably invalid, since in Japanese the word "haiku"
1279 contains three syllables not two.)
1281 This idea was superceded by the rules for escaped whitespace, useful
1282 for `character-level inline markup`_.
1284 * In a `2004-02-22 docutils-develop message`__, Jarno Elonen proposed
1285 a "plain list" syntax (and also provided a patch)::
1288 | President, SuperDuper Corp.
1291 __ http://thread.gmane.org/gmane.text.docutils.devel/1187
1293 This syntax is very natural. However, these "plain lists" seem very
1294 similar to line blocks, and I see so little intrinsic "list-ness"
1295 that I'm loathe to add a new object. I used the term "blurbs" to
1296 remove the "list" connotation from the originally proposed name.
1297 Perhaps line blocks could be refined to add the two properties they
1300 A) long lines wrap nicely
1301 B) HTML output doesn't look like program code in non-CSS web
1304 (A) is an issue of all 3 aspects of Docutils: syntax (construct
1305 behaviour), internal representation, and output. (B) is partly an
1306 issue of internal representation but mostly of output.
1308 ReStructuredText will redefine line blocks with the "|"-quoting
1309 syntax. The following is my current thinking.
1315 Perhaps line block syntax like this would do::
1319 | IMF: not decided yet, but probably one of the following:
1325 Note that the "nested" list does not have nested syntax (the "|" are
1326 not further indented); the leading whitespace would still be
1327 significant somehow (more below). As for long lines in the input,
1328 this could suffice::
1331 | Founder, President, Chief Executive Officer, Cook, Bottle
1332 Washer, and All-Round Great Guy
1336 The lack of "|" on the third line indicates that it's a continuation
1337 of the second line, wrapped.
1339 I don't see much point in allowing arbitrary nested content. Multiple
1340 paragraphs or bullet lists inside a "blurb" doesn't make sense to me.
1341 Simple nested line blocks should suffice.
1344 Internal Representation
1345 -----------------------
1347 Line blocks are currently represented as text blobs as follows::
1349 <!ELEMENT line_block %text.model;>
1350 <!ATTLIST line_block
1354 Instead, we could represent each line by a separate element::
1356 <!ELEMENT line_block (line+)>
1357 <!ATTLIST line_block %basic.atts;>
1359 <!ELEMENT line %text.model;>
1360 <!ATTLIST line %basic.atts;>
1362 We'd keep the significance of the leading whitespace of each line
1363 either by converting it to non-breaking spaces at output, or with a
1364 per-line margin. Non-breaking spaces are simpler (for HTML, anyway)
1365 but kludgey, and wouldn't support indented long lines that wrap. But
1366 should inter-word whitespace (i.e., not leading whitespace) be
1367 preserved? Currently it is preserved in line blocks.
1369 Representing a more complex line block may be tricky::
1371 | But can a bee be said to be
1372 | or not to be an entire bee,
1373 | when half the bee is not a bee,
1374 | due to some ancient injury?
1376 Perhaps the representation could allow for nested line blocks::
1378 <!ELEMENT line_block (line | line_block)+>
1380 With this model, leading whitespace would no longer be significant.
1381 Instead, left margins are implied by the nesting. The example above
1382 could be represented as follows::
1386 But can a bee be said to be
1389 or not to be an entire bee,
1392 when half the bee is not a bee,
1395 due to some ancient injury?
1397 I wasn't sure what to do about even more complex line blocks::
1405 How should that be parsed and nested? Should the first line have
1406 the same nesting level (== indentation in the output) as the fourth
1407 line, or the same as the last line? Mark Nodine suggested that such
1408 line blocks be parsed similarly to complexly-nested block quotes,
1409 which seems reasonable. In the example above, this would result in
1410 the nesting of first line matching the last line's nesting. In
1411 other words, the nesting would be relative to neighboring lines
1418 In HTML, line blocks are currently output as "<pre>" blocks, which
1419 gives us significant whitespace and line breaks, but doesn't allow
1420 long lines to wrap and causes monospaced output without stylesheets.
1421 Instead, we could output "<div>" elements parallelling the
1422 representation above, where each nested <div class="line_block"> would
1423 have an increased left margin (specified in the stylesheet).
1425 Jarno suggested the following HTML output::
1427 <div class="line_block">
1428 <span class="line">First, top level line</span><br class="hidden"/>
1429 <div class="line_block"><span class="hidden"> </span>
1430 <span class="line">Second, once nested</span><br class="hidden"/>
1431 <span class="line">Third, once nested</span><br class="hidden"/>
1437 The ``<br class="hidden" />`` and ``<span
1438 class="hidden"> </span>`` are meant to support non-CSS and
1439 non-graphical browsers. I understand the case for "br", but I'm not
1440 so sure about hidden " ". I question how much effort should be
1441 put toward supporting non-graphical and especially non-CSS browsers,
1442 at least for html4css1.py output.
1444 Should the lines themselves be ``<span>`` or ``<div>``? I don't like
1445 mixing inline and block-level elements.
1451 We'll leave the old implementation in place (via the "line-block"
1452 directive only) until all Writers have been updated to support the new
1453 syntax & implementation. The "line-block" directive can then be
1454 updated to use the new internal representation, and its documentation
1455 will be updated to recommend the new syntax.
1461 The original idea came from Dylan Jay:
1463 ... to use a two level bulleted list with something to
1464 indicate it should be rendered as a table ...
1466 It's an interesting idea. It could be implemented in as a directive
1467 which transforms a uniform two-level list into a table. Using a
1468 directive would allow the author to explicitly set the table's
1469 orientation (by column or by row), the presence of row headers, etc.
1473 1. (Implemented in Docutils 0.3.8).
1475 Bullet-list-tables might look like this::
1487 - If we took the bones out, it wouldn't be crunchy,
1493 This list must be written in two levels. This wouldn't work::
1510 * If we took the bones out...
1512 The above is a single list of 12 items. The blank lines are not
1513 significant to the markup. We'd have to explicitly specify how
1514 many columns or rows to use, which isn't a good idea.
1516 2. Beni Cherniavsky suggested a field list alternative. It could look
1519 .. field-list-table::
1526 - :treat: Albatross!
1530 - :treat: Crunchy Frog!
1532 :descr: If we took the bones out, it wouldn't be
1533 crunchy, now would it?
1535 Column order is determined from the order of fields in the first
1536 row. Field order in all other rows is ignored. As a side-effect,
1537 this allows trivial re-arrangement of columns. By using named
1538 fields, it becomes possible to omit fields in some rows without
1539 losing track of things, which is important for spans.
1541 3. An alternative to two-level bullet lists would be to use enumerated
1542 lists for the table cells::
1554 3. If we took the bones out, it wouldn't be crunchy,
1557 That provides better correspondence between cells in the same
1558 column than does bullet-list syntax, but not as good as field list
1559 syntax. I think that were only field-list-tables available, a lot
1560 of users would use the equivalent degenerate case::
1562 .. field-list-table::
1568 4. Another natural variant is to allow a description list with field
1569 lists as descriptions::
1582 :descr: If we took the bones out, it wouldn't be
1583 crunchy, now would it?
1585 This would make the whole first column a header column ("stub").
1586 It's limited to a single column and a single paragraph fitting on
1587 one source line. Also it wouldn't allow for empty cells or row
1588 spans in the first column. But these are limitations that we could
1589 live with, like those of simple tables.
1591 The List-driven table feature could be done in many ways. Each user
1592 will have their preferred usage. Perhaps a single "list-table"
1593 directive could handle them all, depending on which options and
1594 content are present.
1598 * How to indicate that there's 1 header row? Perhaps two lists? ::
1610 This is probably too subtle though. Better would be a directive
1611 option, like ``:headrows: 1``. An early suggestion for the header
1612 row(s) was to use a directive option::
1614 .. field-list-table::
1619 - :treat: Albatross!
1623 But the table data is at two levels and looks inconsistent.
1625 In general, we cannot extract the header row from field lists' field
1626 names because field names cannot contain everything one might put in
1627 a table cell. A separate header row also allows shorter field names
1628 and doesn't force one to rewrite the whole table when the header
1629 text changes. But for simpler cases, we can offer a ":header:
1630 fields" option, which does extract header cells from field names::
1632 .. field-list-table::
1635 - :Treat: Albatross!
1637 :Description: On a stick!
1639 * How to indicate the column widths? A directive option? ::
1644 Automatic defaults from the text used?
1646 * How to handle row and/or column spans?
1648 In a field list, column-spans can be indicated by specifying the
1649 first and last fields, separated by space-dash-space or ellipsis::
1652 - :foo ... baz: quuux
1654 Commas were proposed for column spans::
1658 But non-adjacent columns become problematic. Should we report an
1659 error, or duplicate the value into each span of adjacent columns (as
1660 was suggested)? The latter suggestion is appealing but may be too
1661 clever. Best perhaps to simply specify the two ends.
1663 It was suggested that comma syntax should be allowed, too, in order
1664 to allow the user to avoid trouble when changing the column order.
1665 But changing the column order of a table with spans is not trivial;
1666 we shouldn't make it easier to mess up.
1668 One possible syntax for row-spans is to simply treat any row where a
1669 field is missing as a row-span from the last row where it appeared.
1670 Leaving a field empty would still be possible by writing a field
1671 with empty content. But this is too implicit.
1673 Another way would be to require an explicit continuation marker
1674 (``...``/``-"-``/``"``?) in all but the first row of a spanned
1675 field. Empty comments could work (".."). If implemented, the same
1676 marker could also be supported in simple tables, which lack
1677 row-spanning abilities.
1679 Explicit markup like ":rowspan:" and ":colspan:" was also suggested.
1681 Sometimes in a table, the first header row contains spans. It may
1682 be necessary to provide a way to specify the column field names
1683 independently of data rows. A directive option would do it.
1685 * We could specify "column-wise" or "row-wise" ordering, with the same
1686 markup structure. For example, with definition data::
1699 - If we took the bones out, it wouldn't be
1700 crunchy, now would it?
1702 * A syntax for _`stubs in grid tables` is easy to imagine::
1704 +------------------------++------------+----------+
1705 | Header row, column 1 || Header 2 | Header 3 |
1706 +========================++============+==========+
1707 | body row 1, column 1 || column 2 | column 3 |
1708 +------------------------++------------+----------+
1710 Or this idea from Nick Moffitt::
1721 Auto-Enumerated Lists
1722 =====================
1724 Implemented 2005-03-24: combination of variation 1 & 2.
1726 The advantage of auto-numbered enumerated lists would be similar to
1727 that of auto-numbered footnotes: lists could be written and rearranged
1728 without having to manually renumber them. The disadvantages are also
1729 the same: input and output wouldn't match exactly; the markup may be
1730 ugly or confusing (depending on which alternative is chosen).
1732 1. Use the "#" symbol. Example::
1738 Advantages: simple, explicit. Disadvantage: enumeration sequence
1739 cannot be specified (limited to arabic numerals); ugly.
1741 2. As a variation on #1, first initialize the enumeration sequence?
1748 Advantages: simple, explicit, any enumeration sequence possible.
1749 Disadvantages: ugly; perhaps confusing with mixed concrete/abstract
1752 3. Alternative suggested by Fred Bremmer, from experience with MoinMoin::
1758 Advantages: enumeration sequence is explicit (could be multiple
1759 "a." or "(I)" tokens). Disadvantages: perhaps confusing; otherwise
1760 erroneous input (e.g., a duplicate item "1.") would pass silently,
1761 either causing a problem later in the list (if no blank lines
1762 between items) or creating two lists (with blanks).
1764 Take this input for example::
1768 1. Unintentional duplicate of item 1.
1772 Currently the parser will produce two list, "1" and "1,2" (no
1773 warnings, because of the presence of blank lines). Using Fred's
1774 notation, the current behavior is "1,1,2 -> 1 1,2" (without blank
1775 lines between items, it would be "1,1,2 -> 1 [WARNING] 1,2"). What
1776 should the behavior be with auto-numbering?
1778 Fred has produced a patch__, whose initial behavior is as follows::
1783 1,2,2,3 -> 1,2,3 [WARNING] 3
1784 1,1,2 -> 1,2 [WARNING] 2
1786 (After the "[WARNING]", the "3" would begin a new list.)
1788 I have mixed feelings about adding this functionality to the spec &
1789 parser. It would certainly be useful to some users (myself
1790 included; I often have to renumber lists). Perhaps it's too
1791 clever, asking the parser to guess too much. What if you *do* want
1792 three one-item lists in a row, each beginning with "1."? You'd
1793 have to use empty comments to force breaks. Also, I question
1794 whether "1,2,2 -> 1,2,3" is optimal behavior.
1796 In response, Fred came up with "a stricter and more explicit rule
1797 [which] would be to only auto-number silently if *all* the
1798 enumerators of a list were identical". In that case::
1801 1,2,2 -> 1,2 [WARNING] 2
1803 1,2,2,3 -> 1,2 [WARNING] 2,3
1804 1,1,2 -> 1,2 [WARNING] 2
1806 Should any start-value be allowed ("3,3,3"), or should
1807 auto-numbered lists be limited to begin with ordinal-1 ("1", "A",
1810 __ http://sourceforge.net/tracker/index.php?func=detail&aid=548802
1811 &group_id=38414&atid=422032
1813 4. Alternative proposed by Tony Ibbs::
1816 #3. Aha - I edited this in later.
1819 The initial proposal required unique enumerators within a list, but
1820 this limits the convenience of a feature of already limited
1821 applicability and convenience. Not a useful requirement; dropped.
1823 Instead, simply prepend a "#" to a standard list enumerator to
1824 indicate auto-enumeration. The numbers (or letters) of the
1825 enumerators themselves are not significant, except:
1827 - as a sequence indicator (arabic, roman, alphabetic; upper/lower),
1829 - and perhaps as a start value (first list item).
1831 Advantages: explicit, any enumeration sequence possible.
1832 Disadvantages: a bit ugly.
1835 Adjacent citation references
1836 ============================
1838 A special case for inline markup was proposed and implemented:
1839 multiple citation references could be joined into one::
1841 [cite1]_[cite2]_ instead of requiring [cite1]_ [cite2]_
1843 However, this was rejected as an unwarranted exception to the rules
1845 (The main motivation for the proposal, grouping citations in the latex writer,
1846 was implemented by recognising the second group in the example above and
1847 transforming it into ``\cite{cite1,cite2}``.)
1850 Inline markup recognition
1851 =========================
1853 Implemented 2011-12-05 (version 0.9):
1854 Extended `inline markup recognition rules`_.
1856 Non-ASCII whitespace, punctuation characters and "international" quotes are
1857 allowed around inline markup (based on `Unicode categories`_). The rules for
1858 ASCII characters were not changed.
1860 Rejected alternatives:
1862 a) Use `Unicode categories`_ for all chars (ASCII or not)
1864 +1 comprehensible, standards based,
1865 -1 many "false positives" need escaping,
1866 -1 not backwards compatible.
1868 b) full backwards compatibility
1870 :Pi: only before start-string
1871 :Pf: only behind end-string
1872 :Po: "conservative" sorting of other punctuation:
1877 +1 backwards compatible,
1878 +1 logical extension of the existing rules,
1879 -1 exception list for "other" punctuation needed,
1880 -1 rules even more complicated,
1881 -1 not clear how to sort "other" punctuation that is currently not
1883 -2 international quoting convention like
1884 »German ›angular‹ quotes« not recognized.
1886 .. _Inline markup recognition rules:
1887 ../../ref/rst/restructuredtext.html#inline-markup-recognition-rules
1888 .. _Unicode categories:
1889 http://www.unicode.org/Public/5.1.0/ucd/UCD.html#General_Category_Values
1899 As a further wrinkle (see `Reworking Explicit Markup (Round 1)`_
1900 above), in the wee hours of 2002-02-28 I posted several ideas for
1901 changes to footnote syntax:
1903 - Change footnote syntax from ``.. [1]`` to ``_[1]``? ...
1904 - Differentiate (with new DTD elements) author-date "citations"
1905 (``[GVR2002]``) from numbered footnotes? ...
1906 - Render footnote references as superscripts without "[]"? ...
1908 These ideas are all related, and suggest changes in the
1909 reStructuredText syntax as well as the docutils tree model.
1911 The footnote has been used for both true footnotes (asides expanding
1912 on points or defining terms) and for citations (references to external
1913 works). Rather than dealing with one amalgam construct, we could
1914 separate the current footnote concept into strict footnotes and
1915 citations. Citations could be interpreted and treated differently
1916 from footnotes. Footnotes would be limited to numerical labels:
1917 manual ("1") and auto-numbered (anonymous "#", named "#label").
1919 The footnote is the only explicit markup construct (starts with ".. ")
1920 that directly translates to a visible body element. I've always been
1921 a little bit uncomfortable with the ".. " marker for footnotes because
1922 of this; ".. " has a connotation of "special", but footnotes aren't
1923 especially "special". Printed texts often put footnotes at the bottom
1924 of the page where the reference occurs (thus "foot note"). Some HTML
1925 designs would leave footnotes to be rendered the same positions where
1926 they're defined. Other online and printed designs will gather
1927 footnotes into a section near the end of the document, converting them
1928 to "endnotes" (perhaps using a directive in our case); but this
1929 "special processing" is not an intrinsic property of the footnote
1930 itself, but a decision made by the document author or processing
1933 Citations are almost invariably collected in a section at the end of a
1934 document or section. Citations "disappear" from where they are
1935 defined and are magically reinserted at some well-defined point.
1936 There's more of a connection to the "special" connotation of the ".. "
1937 syntax. The point at which the list of citations is inserted could be
1938 defined manually by a directive (e.g., ".. citations::"), and/or have
1939 default behavior (e.g., a section automatically inserted at the end of
1940 the document) that might be influenced by options to the Writer.
1949 .. [#] Auto-numbered footnote.
1950 .. [#label] Auto-labeled footnote.
1952 - The syntax proposed in the original 2002-02-28 Doc-SIG post:
1953 remove the ".. ", prefix a "_"::
1956 _[#] Auto-numbered footnote.
1957 _[#label] Auto-labeled footnote.
1959 The leading underscore syntax (earlier dropped because
1960 ``.. _[1]:`` was too verbose) is a useful reminder that footnotes
1961 are hyperlink targets.
1963 - Minimal syntax: remove the ".. [" and "]", prefix a "_", and
1967 _#. Auto-numbered footnote.
1968 _#label. Auto-labeled footnote.
1970 ``_1.``, ``_#.``, and ``_#label.`` are markers,
1973 Footnotes could be rendered something like this in HTML
1975 | 1. This is a footnote. The brackets could be dropped
1976 | from the label, and a vertical bar could set them
1977 | off from the rest of the document in the HTML.
1979 Two-way hyperlinks on the footnote marker ("1." above) would also
1980 help to differentiate footnotes from enumerated lists.
1982 If converted to endnotes (by a directive/transform), a horizontal
1983 half-line might be used instead. Page-oriented output formats
1984 would typically use the horizontal line for true footnotes.
1986 + Footnote references:
1990 [1]_, [#]_, [#label]_
1992 - Minimal syntax to match the minimal footnote syntax above::
1996 As a consequence, pure-numeric hyperlink references would not be
1997 possible; they'd be interpreted as footnote references.
1999 + Citation references: no change is proposed from the current footnote
2006 - Current syntax (footnote syntax)::
2008 .. [GVR2001] Python Documentation; van Rossum, Drake, et al.;
2009 http://www.python.org/doc/
2011 - Possible new syntax::
2013 _[GVR2001] Python Documentation; van Rossum, Drake, et al.;
2014 http://www.python.org/doc/
2017 Docutils: Python Documentation Utilities project; Goodger
2018 et al.; http://docutils.sourceforge.net/
2020 Without the ".. " marker, subsequent lines would either have to
2021 align as in one of the above, or we'd have to allow loose
2022 alignment (I'd rather not)::
2024 _[GVR2001] Python Documentation; van Rossum, Drake, et al.;
2025 http://www.python.org/doc/
2027 I proposed adopting the "minimal" syntax for footnotes and footnote
2028 references, and adding citations and citation references to
2029 reStructuredText's repertoire. The current footnote syntax for
2030 citations is better than the alternatives given.
2032 From a reply by Tony Ibbs on 2002-03-01:
2034 However, I think easier with examples, so let's create one::
2036 Fans of Terry Pratchett are perhaps more likely to use
2037 footnotes [1]_ in their own writings than other people
2038 [2]_. Of course, in *general*, one only sees footnotes
2039 in academic or technical writing - it's use in fiction
2040 and letter writing is not normally considered good
2041 style [4]_, particularly in emails (not a medium that
2042 lends itself to footnotes).
2044 .. [1] That is, little bits of referenced text at the
2046 .. [2] Because Terry himself does, of course [3]_.
2047 .. [3] Although he has the distinction of being
2048 *funny* when he does it, and his fans don't always
2050 .. [4] Presumably because it detracts from linear
2051 reading of the text - this is, of course, the point.
2053 and look at it with the second syntax proposal::
2055 Fans of Terry Pratchett are perhaps more likely to use
2056 footnotes [1]_ in their own writings than other people
2057 [2]_. Of course, in *general*, one only sees footnotes
2058 in academic or technical writing - it's use in fiction
2059 and letter writing is not normally considered good
2060 style [4]_, particularly in emails (not a medium that
2061 lends itself to footnotes).
2063 _[1] That is, little bits of referenced text at the
2065 _[2] Because Terry himself does, of course [3]_.
2066 _[3] Although he has the distinction of being
2067 *funny* when he does it, and his fans don't always
2069 _[4] Presumably because it detracts from linear
2070 reading of the text - this is, of course, the point.
2072 (I note here that if I have gotten the indentation of the
2073 footnotes themselves correct, this is clearly not as nice. And if
2074 the indentation should be to the left margin instead, I like that
2077 and the third (new) proposal::
2079 Fans of Terry Pratchett are perhaps more likely to use
2080 footnotes 1_ in their own writings than other people
2081 2_. Of course, in *general*, one only sees footnotes
2082 in academic or technical writing - it's use in fiction
2083 and letter writing is not normally considered good
2084 style 4_, particularly in emails (not a medium that
2085 lends itself to footnotes).
2087 _1. That is, little bits of referenced text at the
2089 _2. Because Terry himself does, of course 3_.
2090 _3. Although he has the distinction of being
2091 *funny* when he does it, and his fans don't always
2093 _4. Presumably because it detracts from linear
2094 reading of the text - this is, of course, the point.
2096 I think I don't, in practice, mind the targets too much (the use
2097 of a dot after the number helps a lot here), but I do have a
2098 problem with the body text, in that I don't naturally separate out
2099 the footnotes as different than the rest of the text - instead I
2100 keep wondering why there are numbers interspered in the text. The
2101 use of brackets around the numbers ([ and ]) made me somehow parse
2102 the footnote references as "odd" - i.e., not part of the body text
2103 - and thus both easier to skip, and also (paradoxically) easier to
2104 pick out so that I could follow them.
2106 Thus, for the moment (and as always susceptible to argument), I'd
2107 say -1 on the new form of footnote reference (i.e., I much prefer
2108 the existing ``[1]_`` over the proposed ``1_``), and ambivalent
2109 over the proposed target change.
2111 That leaves David's problem of wanting to distinguish footnotes
2112 and citations - and the only thing I can propose there is that
2113 footnotes are numeric or # and citations are not (which, as a
2114 human being, I can probably cope with!).
2116 From a reply by Paul Moore on 2002-03-01:
2118 I think the current footnote syntax ``[1]_`` is *exactly* the
2119 right balance of distinctness vs unobtrusiveness. I very
2120 definitely don't think this should change.
2122 On the target change, it doesn't matter much to me.
2124 From a further reply by Tony Ibbs on 2002-03-01, referring to the
2125 "[1]" form and actual usage in email:
2127 Clearly this is a form people are used to, and thus we should
2128 consider it strongly (in the same way that the usage of ``*..*``
2129 to mean emphasis was taken partly from email practise).
2131 Equally clearly, there is something "magical" for people in the
2132 use of a similar form (i.e., ``[1]``) for both footnote reference
2133 and footnote target - it seems natural to keep them similar.
2137 I think that this established plaintext usage leads me to strongly
2138 believe we should retain square brackets at both ends of a
2139 footnote. The markup of the reference end (a single trailing
2140 underscore) seems about as minimal as we can get away with. The
2141 markup of the target end depends on how one envisages the thing -
2142 if ".." means "I am a target" (as I tend to see it), then that's
2143 good, but one can also argue that the "_[1]" syntax has a neat
2144 symmetry with the footnote reference itself, if one wishes (in
2145 which case ".." presumably means "hidden/special" as David seems
2146 to think, which is why one needs a ".." *and* a leading underline
2147 for hyperlink targets.
2149 Given the persuading arguments voiced, we'll leave footnote & footnote
2150 reference syntax alone. Except that these discussions gave rise to
2151 the "auto-symbol footnote" concept, which has been added. Citations
2152 and citation references have also been added.
2155 Syntax for Questions & Answers
2156 ==============================
2158 Implement as a generic two-column marked list? As a standalone
2159 (non-directive) construct? (Is the markup ambiguous?) Add support to
2162 New elements would be required. Perhaps::
2164 <!ELEMENT question_list (question_list_item+)>
2165 <!ATTLIST question_list
2166 numbering (none | local | global)
2168 start NUMBER #IMPLIED>
2169 <!ELEMENT question_list_item (question, answer*)>
2170 <!ELEMENT question %text.model;>
2171 <!ELEMENT answer (%body.elements;)+>
2173 Originally I thought of implementing a Q&A list with special syntax::
2177 A: You are a question-and-answer
2182 A: I am the omniscient "we".
2184 Where each "Q" and "A" could also be numbered (e.g., "Q1"). However,
2185 a simple enumerated or bulleted list will do just fine for syntax. A
2186 directive could treat the list specially; e.g. the first paragraph
2187 could be treated as a question, the remainder as the answer (multiple
2188 answers could be represented by nested lists). Without special
2189 syntax, this directive becomes low priority.
2191 As described in the FAQ__, no special syntax or directive is needed
2192 for this application.
2194 __ http://docutils.sf.net/FAQ.html
2195 #how-can-i-mark-up-a-faq-or-other-list-of-questions-answers
2202 Reworking Explicit Markup (Round 2)
2203 ===================================
2205 See `Reworking Explicit Markup (Round 1)`_ for an earlier discussion.
2207 In April 2004, a new thread becan on docutils-develop: `Inconsistency
2208 in RST markup`__. Several arguments were made; the first argument
2209 begat later arguments. Below, the arguments are paraphrased "in
2210 quotes", with responses.
2212 __ http://thread.gmane.org/gmane.text.docutils.devel/1386
2214 1. References and targets take this form::
2218 .. _targetname: stuff
2220 But footnotes, "which generate links just like targets do", are
2227 "Footnotes should be written as"::
2233 But they're not the same type of animal. That's not a "footnote
2234 target", it's a *footnote*. Being a target is not a footnote's
2235 primary purpose (an arguable point). It just happens to grow a
2236 target automatically, for convenience. Just as a section title::
2241 isn't a "title target", it's a *title*, which happens to grow a
2242 target automatically. The consistency is there, it's just deeper
2243 than at first glance.
2245 Also, ".. [1]" was chosen for footnote syntax because it closely
2246 resembles one form of actual footnote rendering. ".. _[1]:" is too
2247 verbose; excessive punctuation is required to get the job done.
2249 For more of the reasoning behind the syntax, see `Problems With
2250 StructuredText (Hyperlinks) <problems.html#hyperlinks>`__ and
2251 `Reworking Footnotes`_.
2253 2. "I expect directives to also look like ``.. this:`` [one colon]
2254 because that also closely parallels the link and footnote target
2257 There are good reasons for the two-colon syntax:
2259 Two colons are used after the directive type for these reasons:
2261 - Two colons are distinctive, and unlikely to be used in common
2264 - Two colons avoids clashes with common comment text like::
2266 .. Danger: modify at your own risk!
2268 - If an implementation of reStructuredText does not recognize a
2269 directive (i.e., the directive-handler is not installed), a
2270 level-3 (error) system message is generated, and the entire
2271 directive block (including the directive itself) will be
2272 included as a literal block. Thus "::" is a natural choice.
2274 -- `restructuredtext.html#directives
2275 <../../ref/rst/restructuredtext.html#directives>`__
2277 The last reason is not particularly compelling; it's more of a
2278 convenient coincidence or mnemonic.
2280 3. "Comments always seemed too easy. I almost never write comments.
2281 I'd have no problem writing '.. comment:' in front of my comments.
2282 In fact, it would probably be more readable, as comments *should*
2283 be set off strongly, because they are very different from normal
2286 Many people do use comments though, and some applications of
2287 reStructuredText require it. For example, all reStructuredText
2288 PEPs (and this document!) have an Emacs stanza at the bottom, in a
2289 comment. Having to write ".. comment::" would be very obtrusive.
2291 Comments *should* be dirt-easy to do. It should be easy to
2292 "comment out" a block of text. Comments in programming languages
2293 and other markup languages are invariably easy.
2295 Any author is welcome to preface their comments with "Comment:" or
2296 "Do Not Print" or "Note to Editor" or anything they like. A
2297 "comment" directive could easily be implemented. It might be
2298 confused with admonition directives, like "note" and "caution"
2299 though. In unrelated (and unpublished and unfinished) work, adding
2300 a "comment" directive as a true document element was considered::
2302 If structure is necessary, we could use a "comment" directive
2303 (to avoid nonsensical DTD changes, the "comment" directive
2304 could produce an untitled topic element).
2306 4. "One of the goals of reStructuredText is to be *readable* by people
2307 who don't know it. This construction violates that: it is not at
2308 all obvious to the uninitiated that text marked by '..' is a
2309 comment. On the other hand, '.. comment:' would be totally
2312 Totally transparent, perhaps, but also very obtrusive. Another of
2313 `reStructuredText's goals`_ is to be unobtrusive, and
2314 ".. comment::" would violate that. The goals of reStructuredText
2315 are many, and they conflict. Determining the right set of goals
2316 and finding solutions that best fit is done on a case-by-case
2319 Even readability is has two aspects. Being readable without any
2320 prior knowledge is one. Being as easily read in raw form as in
2321 processed form is the other. ".." may not contribute to the former
2322 aspect, but ".. comment::" would certainly detract from the latter.
2325 .. _reStructuredText's goals: ../../ref/rst/introduction.html#goals
2327 5. "Recently I sent someone an rst document, and they got confused; I
2328 had to explain to them that '..' marks comments, *unless* it's a
2331 The explanation of directives *is* roundabout, defining comments in
2332 terms of not being other things. That's definitely a wart.
2334 6. "Under the current system, a mistyped directive (with ':' instead
2335 of '::') will be silently ignored. This is an error that could
2336 easily go unnoticed."
2338 A parser option/setting like "--comments-on-stderr" would help.
2340 7. "I'd prefer to see double-dot-space / command / double-colon as the
2341 standard Docutils markup-marker. It's unusual enough to avoid
2342 being accidentally used. Everything that starts with a double-dot
2343 should end with a double-colon."
2345 That would increase the punctuation verbosity of some constructs
2348 8. Edward Loper proposed the following plan for backwards
2351 1. ".. foo" will generate a deprecation warning to stderr, and
2352 nothing in the output (no system messages).
2353 2. ".. foo: bar" will be treated as a directive foo. If there
2354 is no foo directive, then do the normal error output.
2355 3. ".. foo:: bar" will generate a deprecation warning to
2356 stderr, and be treated as a directive. Or leave it valid?
2358 So some existing documents might start printing deprecation
2359 warnings, but the only existing documents that would *break*
2360 would be ones that say something like::
2362 .. warning: this should be a comment
2366 .. warning:: this should be a comment
2368 Here, we're trading fairly common a silent error (directive
2369 falsely treated as a comment) for a fairly uncommon explicitly
2370 flagged error (comment falsely treated as directive). To make
2371 things even easier, we could add a sentence to the
2372 unknown-directive error. Something like "If you intended to
2373 create a comment, please use '.. comment:' instead".
2375 On one hand, I understand and sympathize with the points raised. On
2376 the other hand, I think the current syntax strikes the right balance
2377 (but I acknowledge a possible lack of objectivity). On the gripping
2378 hand, the comment and directive syntax has become well established, so
2379 even if it's a wart, it may be a wart we have to live with.
2381 Making any of these changes would cause a lot of breakage or at least
2382 deprecation warnings. I'm not sure the benefit is worth the cost.
2384 For now, we'll treat this as an unresolved legacy issue.
2391 Nested Inline Markup
2392 ====================
2394 These are collected notes on a long-discussed issue. The original
2395 mailing list messages should be referred to for details.
2397 * In a 2001-10-31 discussion I wrote:
2399 Try, for example, `Ed Loper's 2001-03-21 post`_, which details
2400 some rules for nested inline markup. I think the complexity is
2401 prohibitive for the marginal benefit. (And if you can understand
2402 that tree without going mad, you're a better man than I. ;-)
2404 Inline markup is already fragile. Allowing nested inline markup
2405 would only be asking for trouble IMHO. If it proves absolutely
2406 necessary, it can be added later. The rules for what can appear
2407 inside what must be well thought out first though.
2409 .. _Ed Loper's 2001-03-21 post:
2410 http://mail.python.org/pipermail/doc-sig/2001-March/001487.html
2412 -- http://mail.python.org/pipermail/doc-sig/2001-October/002354.html
2414 * In a 2001-11-09 Doc-SIG post, I wrote:
2416 The problem is that in the
2417 what-you-see-is-more-or-less-what-you-get markup language that
2418 is reStructuredText, the symbols used for inline markup ("*",
2419 "**", "`", "``", etc.) may preclude nesting.
2421 I've rethought this position. Nested markup is not precluded, just
2422 tricky. People and software parse "double and 'single' quotes" all
2423 the time. Continuing,
2425 I've thought over how we might implement nested inline
2426 markup. The first algorithm ("first identify the outer inline
2427 markup as we do now, then recursively scan for nested inline
2428 markup") won't work; counterexamples were given in my `last post
2429 <http://mail.python.org/pipermail/doc-sig/2001-November/002363.html>`__.
2431 The second algorithm makes my head hurt::
2434 scan for start-string
2437 scan for start or end string
2438 if new start string found:
2440 elif matching end string found:
2442 elif non-matching end string found:
2443 if its a markup error:
2445 elif the initial start-string was misinterpreted:
2446 # e.g. in this case: ***strong** in emphasis*
2447 restart with the other interpretation
2448 # but it might be several layers back ...
2451 This is similar to how the parser does section title
2452 recognition, but sections are much more regular and
2455 Bottom line is, I don't think the benefits are worth the effort,
2456 even if it is possible. I'm not going to try to write the code,
2457 at least not now. If somebody codes up a consistent, working,
2458 general solution, I'll be happy to consider it.
2460 -- http://mail.python.org/pipermail/doc-sig/2001-November/002388.html
2462 * In a `2003-05-06 Docutils-Users post`__ Paul Tremblay proposed a new
2463 syntax to allow for easier nesting. It eventually evolved into
2468 The duplication with the existing interpreted text syntax is
2471 __ http://article.gmane.org/gmane.text.docutils.user/317
2473 * Could the parser be extended to parse nested interpreted text? ::
2475 :emphasis:`Some emphasized text with :strong:`some more
2476 emphasized text` in it and **perhaps** :reference:`a link``
2478 * In a `2003-06-18 Docutils-Develop post`__, Mark Nodine reported on
2479 his implementation of a form of nested inline markup in his
2480 Perl-based parser (unpublished). He brought up some interesting
2481 ideas. The implementation was flawed, however, by the change in
2482 semantics required for backslash escapes.
2484 __ http://article.gmane.org/gmane.text.docutils.devel/795
2486 * Docutils-develop threads between David Abrahams, David Goodger, and
2487 Mark Nodine (beginning 2004-01-16__ and 2004-01-19__) hashed out
2488 many of the details of a potentially successful implementation, as
2489 described below. David Abrahams checked in code to the "nesting"
2490 branch of CVS, awaiting thorough review.
2492 __ http://thread.gmane.org/gmane.text.docutils.devel/1102
2493 __ http://thread.gmane.org/gmane.text.docutils.devel/1125
2495 It may be possible to accomplish nested inline markup in general with
2496 a more powerful inline markup parser. There may be some issues, but
2497 I'm not averse to the idea of nested inline markup in general. I just
2498 don't have the time or inclination to write a new parser now. Of
2499 course, a good patch would be welcome!
2501 I envisage something like this. Explicit-role interpreted text must
2502 be nestable. Prefix-based is probably preferred, since suffix-based
2503 will look like inline literals::
2505 ``text`:role1:`:role2:
2507 But it can be disambiguated, so it ought to be left up to the author::
2509 `\ `text`:role1:`:role2:
2511 In addition, other forms of inline markup may be nested if
2514 *emphasized ``literal`` and |substitution ref| and link_*
2516 IOW, the parser ought to be as permissive as possible.
2519 Index Entries & Indexes
2520 =======================
2522 Were I writing a book with an index, I guess I'd need two
2523 different kinds of index targets: inline/implicit and
2524 out-of-line/explicit. For example::
2526 In this `paragraph`:index:, several words are being
2527 `marked`:index: inline as implicit `index`:index:
2533 The explicit index directives above would refer to
2534 this paragraph. It might also make sense to allow multiple
2535 entries in an ``index`` directive:
2541 The words "paragraph", "marked", and "index" would become index
2542 entries pointing at the words in the first paragraph. The index
2543 entry words appear verbatim in the text. (Don't worry about the
2544 ugly ":index:" part; if indexing is the only/main application of
2545 interpreted text in your documents, it can be implicit and
2546 omitted.) The two directives provide manual indexing, where the
2547 index entry words ("markup" and "syntax") do not appear in the
2548 main text. We could combine the two directives into one::
2550 .. index:: markup; syntax
2552 Semicolons instead of commas because commas could *be* part of the
2553 index target, like::
2555 .. index:: van Rossum, Guido
2557 Another reason for index directives is because other inline markup
2558 wouldn't be possible within inline index targets.
2560 Sometimes index entries have multiple levels. Given::
2562 .. index:: statement syntax: expression statements
2564 In a hypothetical index, combined with other entries, it might
2568 expression statements ..... 56
2569 assignment ................ 57
2570 simple statements ......... 58
2571 compound statements ....... 60
2573 Inline multi-level index targets could be done too. Perhaps
2576 When dealing with `expression statements <statement syntax:>`,
2577 we must remember ...
2579 The opposite sense could also be possible::
2581 When dealing with `index entries <:multi-level>`, there are
2582 many permutations to consider.
2584 Also "see / see also" index entries.
2590 .. index:: paragraph
2592 (The "index" directive above actually targets the *preceding*
2593 object.) The directive should produce something like this XML::
2596 <index_entry text="paragraph"/>
2600 This kind of content model would also allow true inline
2603 Here's a `paragraph`:index:.
2605 If the "index" role were the default for the application, it could be
2608 Here's a `paragraph`.
2610 Both of these would result in this XML::
2613 Here's a <index_entry>paragraph</index_entry>.
2617 from 2002-06-24 docutils-develop posts
2618 --------------------------------------
2620 If all of your index entries will appear verbatim in the text,
2621 this should be sufficient. If not (e.g., if you want "Van Rossum,
2622 Guido" in the index but "Guido van Rossum" in the text), we'll
2623 have to figure out a supplemental mechanism, perhaps using
2626 I've thought a bit more on this, and I came up with two possibilities:
2628 1. Using interpreted text, embed the index entry text within the
2631 ... by `Guido van Rossum [Van Rossum, Guido]` ...
2633 The problem with this is obvious: the text becomes cluttered and
2634 hard to read. The processed output would drop the text in
2635 brackets, which goes against the spirit of interpreted text.
2637 2. Use substitutions::
2639 ... by |Guido van Rossum| ...
2641 .. |Guido van Rossum| index:: Van Rossum, Guido
2643 A problem with this is that each substitution definition must have
2644 a unique name. A subsequent ``.. |Guido van Rossum| index:: BDFL``
2645 would be illegal. Some kind of anonymous substitution definition
2646 mechanism would be required, but I think that's going too far.
2648 Both of these alternatives are flawed. Any other ideas?
2655 This is the realm of the possible but questionably probable. These
2656 ideas are kept here as a record of what has been proposed, for
2657 posterity and in case any of them prove to be useful.
2660 Compound Enumerated Lists
2661 =========================
2663 Allow for compound enumerators, such as "1.1." or "1.a." or "1(a)", to
2664 allow for nested enumerated lists without indentation?
2670 Allow for variant styles by interpreting indented lists as if they
2671 weren't indented? For example, currently the list below will be
2672 parsed as a list within a block quote::
2679 But a lot of people seem to write that way, and HTML browsers make it
2680 look as if that's the way it should be. The parser could check the
2681 contents of block quotes, and if they contain only a single list,
2682 remove the block quote wrapper. There would be two problems:
2684 1. What if we actually *do* want a list inside a block quote?
2686 2. What if such a list comes immediately after an indented construct,
2687 such as a literal block?
2689 Both could be solved using empty comments (problem 2 already exists
2690 for a block quote after a literal block). But that's a hack.
2692 Perhaps a runtime setting, allowing or disabling this convenience,
2693 would be appropriate. But that raises issues too:
2695 User A, who writes lists indented (and their config file is set up
2696 to allow it), sends a file to user B, who doesn't (and their
2697 config file disables indented lists). The result of processing by
2698 the two users will be different.
2700 It may seem minor, but it adds ambiguity to the parser, which is bad.
2702 See the `Doc-SIG discussion starting 2001-04-18`__ with Ed Loper's
2703 "Structuring: a summary; and an attempt at EBNF", item 4 (and
2704 follow-ups, here__ and here__). Also `docutils-users, 2003-02-17`__
2705 and `beginning 2003-08-04`__.
2707 __ http://mail.python.org/pipermail/doc-sig/2001-April/001776.html
2708 __ http://mail.python.org/pipermail/doc-sig/2001-April/001789.html
2709 __ http://mail.python.org/pipermail/doc-sig/2001-April/001793.html
2710 __ http://sourceforge.net/mailarchive/message.php?msg_id=3838913
2711 __ http://sf.net/mailarchive/forum.php?thread_id=2957175&forum_id=11444
2714 Sloppy Indentation of List Items
2715 ================================
2717 Perhaps the indentation shouldn't be so strict. Currently, this is
2723 Anything wrong with this? ::
2732 Block quote. (no good: requires some indent relative to first
2737 2. Have to carefully define where the literal block ends::
2743 Hmm... Non-strict indentation isn't such a good idea.
2746 Lazy Indentation of List Items
2747 ==============================
2749 Another approach: Going back to the first draft of reStructuredText
2750 (2000-11-27 post to Doc-SIG)::
2752 - This is the fourth item of the main list (no blank line above).
2753 The second line of this item is not indented relative to the
2754 bullet, which precludes it from having a second paragraph.
2756 Change that to *require* a blank line above and below, to reduce
2757 ambiguity. This "loosening" may be added later, once the parser's
2758 been nailed down. However, a serious drawback of this approach is to
2759 limit the content of each list item to a single paragraph.
2762 David's Idea for Lazy Indentation
2763 ---------------------------------
2765 Consider a paragraph in a word processor. It is a single logical line
2766 of text which ends with a newline, soft-wrapped arbitrarily at the
2767 right edge of the page or screen. We can think of a plaintext
2768 paragraph in the same way, as a single logical line of text, ending
2769 with two newlines (a blank line) instead of one, and which may contain
2770 arbitrary line breaks (newlines) where it was accidentally
2771 hard-wrapped by an application. We can compensate for the accidental
2772 hard-wrapping by "unwrapping" every unindented second and subsequent
2773 line. The indentation of the first line of a paragraph or list item
2774 would determine the indentation for the entire element. Blank lines
2775 would be required between list items when using lazy indentation.
2777 The following example shows the lazy indentation of multiple body
2780 - This is the first paragraph
2781 of the first list item.
2783 Here is the second paragraph
2784 of the first list item.
2786 - This is the first paragraph
2787 of the second list item.
2789 Here is the second paragraph
2790 of the second list item.
2792 A more complex example shows the limitations of lazy indentation::
2794 - This is the first paragraph
2795 of the first list item.
2797 Next is a definition list item:
2800 Definition. The indentation of the term is
2801 required, as is the indentation of the definition's
2804 When the definition extends to more than
2805 one line, lazy indentation may occur. (This is the second
2806 paragraph of the definition.)
2808 - This is the first paragraph
2809 of the second list item.
2811 - Here is the first paragraph of
2812 the first item of a nested list.
2814 So this paragraph would be outside of the nested list,
2815 but inside the second list item of the outer list.
2817 But this paragraph is not part of the list at all.
2819 And the ambiguity remains::
2821 - Look at the hyphen at the beginning of the next line
2822 - is it a second list item marker, or a dash in the text?
2824 Similarly, we may want to refer to numbers inside enumerated
2827 1. How many socks in a pair? There are
2828 2. How many pants in a pair? Exactly
2831 Literal blocks and block quotes would still require consistent
2832 indentation for all their lines. For block quotes, we might be able
2833 to get away with only requiring that the first line of each contained
2834 element be indented. For example::
2838 This is a paragraph inside a block quote.
2839 Second and subsequent lines need not be indented at all.
2841 - A bullet list inside
2844 Second paragraph of the
2845 bullet list inside the block quote.
2847 Although feasible, this form of lazy indentation has problems. The
2848 document structure and hierarchy is not obvious from the indentation,
2849 making the source plaintext difficult to read. This will also make
2850 keeping track of the indentation while writing difficult and
2851 error-prone. However, these problems may be acceptable for Wikis and
2852 email mode, where we may be able to rely on less complex structure
2853 (few nested lists, for example).
2856 Multiple Roles in Interpreted Text
2857 ==================================
2859 In reStructuredText, inline markup cannot be nested (yet; `see
2860 above`__). This also applies to interpreted text. In order to
2861 simultaneously combine multiple roles for a single piece of text, a
2862 syntax extension would be necessary. Ideas:
2866 `interpreted text`:role1,role2:
2868 2. Suggested by Jason Diamond::
2870 `interpreted text`:role1:role2:
2872 If a document is so complex as to require nested inline markup,
2873 perhaps another markup system should be considered. By design,
2874 reStructuredText does not have the flexibility of XML.
2876 __ `Nested Inline Markup`_
2879 Parameterized Interpreted Text
2880 ==============================
2882 In some cases it may be expedient to pass parameters to interpreted
2883 text, analogous to function calls. Ideas:
2885 1. Parameterize the interpreted text role itself (suggested by Jason
2888 `interpreted text`:role1(foo=bar):
2890 Positional parameters could also be supported::
2892 `CSS`:acronym(Cascading Style Sheets): is used for HTML, and
2893 `CSS`:acronym(Content Scrambling System): is used for DVDs.
2895 Technical problem: current interpreted text syntax does not
2896 recognize roles containing whitespace. Design problem: this smells
2897 like programming language syntax, but reStructuredText is not a
2898 programming language.
2900 2. Put the parameters inside the interpreted text::
2902 `CSS (Cascading Style Sheets)`:acronym: is used for HTML, and
2903 `CSS (Content Scrambling System)`:acronym: is used for DVDs.
2905 Although this could be defined on an individual basis (per role),
2906 we ought to have a standard. Hyperlinks with embedded URIs already
2907 use angle brackets; perhaps they could be used here too::
2909 `CSS <Cascading Style Sheets>`:acronym: is used for HTML, and
2910 `CSS <Content Scrambling System>`:acronym: is used for DVDs.
2912 Do angle brackets connote URLs too much for this to be acceptable?
2913 How about the "tag" connotation -- does it save them or doom them?
2915 3. `Nested inline markup`_ could prove useful here::
2917 `CSS :def:`Cascading Style Sheets``:acronym: is used for HTML,
2918 and `CSS :def:`Content Scrambling System``:acronym: is used for
2921 Inline markup roles could even define the default roles of nested
2922 inline markup, allowing this cleaner syntax::
2924 `CSS `Cascading Style Sheets``:acronym: is used for HTML, and
2925 `CSS `Content Scrambling System``:acronym: is used for DVDs.
2927 Does this push inline markup too far? Readability becomes a serious
2928 issue. Substitutions may provide a better alternative (at the expense
2929 of verbosity and duplication) by pulling the details out of the text
2932 |CSS| is used for HTML, and |CSS-DVD| is used for DVDs.
2934 .. |CSS| acronym:: Cascading Style Sheets
2935 .. |CSS-DVD| acronym:: Content Scrambling System
2938 ----------------------------------------------------------------------
2940 This whole idea may be going beyond the scope of reStructuredText.
2941 Documents requiring this functionality may be better off using XML or
2942 another markup system.
2944 This argument comes up regularly when pushing the envelope of
2945 reStructuredText syntax. I think it's a useful argument in that it
2946 provides a check on creeping featurism. In many cases, the resulting
2947 verbosity produces such unreadable plaintext that there's a natural
2948 desire *not* to use it unless absolutely necessary. It's a matter of
2949 finding the right balance.
2952 Syntax for Interpreted Text Role Bindings
2953 =========================================
2955 The following syntax (idea from Jeffrey C. Jacobs) could be used to
2956 associate directives with roles::
2958 .. :rewrite: class:: rewrite
2960 `She wore ribbons in her hair and it lay with streaks of
2963 The syntax is similar to that of substitution declarations, and the
2964 directive/role association may resolve implementation issues. The
2965 semantics, ramifications, and implementation details would need to be
2968 The example above would implement the "rewrite" role as adding a
2969 ``class="rewrite"`` attribute to the interpreted text ("inline"
2970 element). The stylesheet would then pick up on the "class" attribute
2971 to do the actual formatting.
2973 The advantage of the new syntax would be flexibility. Uses other than
2974 "class" may present themselves. The disadvantage is complexity:
2975 having to implement new syntax for a relatively specialized operation,
2976 and having new semantics in existing directives ("class::" would do
2977 something different).
2979 The `"role" directive`__ has been implemented.
2981 __ ../../ref/rst/directives.html#role
2984 Character Processing
2985 ====================
2987 Several people have suggested adding some form of character processing
2988 to reStructuredText:
2990 * Some sort of automated replacement of ASCII sequences:
2992 - ``--`` to em-dash (or ``--`` to en-dash, and ``---`` to em-dash).
2993 - Convert quotes to curly quote entities. (Essentially impossible
2994 for HTML? Unnecessary for TeX.)
2995 - Various forms of ``:-)`` to smiley icons.
2996 - ``"\ "`` to . Problem with line-wrapping though: it could
2997 end up escaping the newline.
2998 - Escaped newlines to <BR>.
2999 - Escaped period or quote or dash as a disappearing catalyst to
3000 allow character-level inline markup?
3002 * XML-style character entities, such as "©" for the copyright
3005 Docutils has no need of a character entity subsystem. Supporting
3006 Unicode and text encodings, character entities should be directly
3007 represented in the text: a copyright symbol should be represented by
3008 the copyright symbol character. If this is not possible in an
3009 authoring environment, a pre-processing stage can be added, or a table
3010 of substitution definitions can be devised.
3012 A "unicode" directive has been implemented to allow direct
3013 specification of esoteric characters. In combination with the
3014 substitution construct, "include" files defining common sets of
3015 character entities can be defined and used. `A set of character
3016 entity set definition files have been defined`__ (`tarball`__).
3017 There's also `a description and instructions for use`__.
3019 __ http://docutils.sf.net/tmp/charents/
3020 __ http://docutils.sf.net/tmp/charents.tgz
3021 __ http://docutils.sf.net/tmp/charents/README.html
3023 To allow for `character-level inline markup`_, a limited form of
3024 character processing has been added to the spec and parser: escaped
3025 whitespace characters are removed from the processed document. Any
3026 further character processing will be of this functional type, rather
3027 than of the character-encoding type.
3029 .. _character-level inline markup:
3030 ../../ref/rst/restructuredtext.html#character-level-inline-markup
3034 .. text-replace:: "pattern" "replacement"
3036 - Support Unicode "U+XXXX" codes.
3037 - Support regexps, perhaps with alternative "regexp-replace"
3039 - Flags for regexps; ":flags:" option, or individuals.
3040 - Specifically, should the default be case-sensistive or
3047 * Should ^L (or something else in reST) be defined to mean
3048 force/suggest page breaks in whatever output we have?
3050 A "break" or "page-break" directive would be easy to add. A new
3051 doctree element would be required though (perhaps "break"). The
3052 final behavior would be up to the Writer. The directive argument
3053 could be one of page/column/recto/verso for added flexibility.
3055 Currently ^L (Python's ``\f``) characters are treated as whitespace.
3056 They're converted to single spaces, actually, as are vertical tabs
3057 (^K, Python's ``\v``). It would be possible to recognize form feeds
3058 as markup, but it requires some thought and discussion first. Are
3059 there any downsides? Many editing environments do not allow the
3060 insertion of control characters. Will it cause any harm? It would
3061 be useful as a shorthand for the directive.
3063 It's common practice to use ^L before Emacs "Local Variables"
3070 indent-tabs-mode: nil
3071 sentence-end-double-space: t
3075 These are already present in many PEPs and Docutils project
3076 documents. From the Emacs manual (info):
3078 A "local variables list" goes near the end of the file, in the
3079 last page. (It is often best to put it on a page by itself.)
3081 It would be unfortunate if this construct caused a final blank page
3082 to be generated (for those Writers that recognize the page breaks).
3083 We'll have to add a transform that looks for a "break" plus zero or
3084 more comments at the end of a document, and removes them.
3086 Probably a bad idea because there is no such thing as a page in a
3087 generic document format.
3089 * Could the "break" concept above be extended to inline forms?
3090 E.g. "^L" in the middle of a sentence could cause a line break.
3091 Only recognize it at the end of a line (i.e., ``\f\n``)?
3093 Or is formfeed inappropriate? Perhaps vertical tab (``\v``), but
3094 even that's a stretch. Can't use carriage returns, since they're
3095 commonly used for line endings.
3097 Probably a bad idea as well because we do not want to use control
3098 characters for well-readable and well-writable markup, and after all
3099 we have the line block syntax for line breaks.
3105 Add ``^superscript^`` inline markup? The only common non-markup uses
3106 of "^" I can think of are as short hand for "superscript" itself and
3107 for describing control characters ("^C to cancel"). The former
3108 supports the proposed syntax, and it could be argued that the latter
3109 ought to be literal text anyhow (e.g. "``^C`` to cancel").
3111 However, superscripts are seldom needed, and new syntax would break
3112 existing documents. When it's needed, the ``:superscript:``
3113 (``:sup:``) role can we used as well.
3119 Add the following directives?
3121 - "exec": Execute Python code & insert the results. Call it
3122 "python" to allow for other languages?
3124 - "system": Execute an ``os.system()`` call, and insert the results
3125 (possibly as a literal block). Definitely dangerous! How to make
3126 it safe? Perhaps such processing should be left outside of the
3127 document, in the user's production system (a makefile or a script or
3128 whatever). Or, the directive could be disabled by default and only
3129 enabled with an explicit command-line option or config file setting.
3130 Even then, an interactive prompt may be useful, such as:
3132 The file.txt document you are processing contains a "system"
3133 directive requesting that the ``sudo rm -rf /`` command be
3134 executed. Allow it to execute? (y/N)
3136 - "eval": Evaluate an expression & insert the text. At parse
3137 time or at substitution time? Dangerous? Perhaps limit to canned
3138 macros; see text.date_.
3140 .. _text.date: ../todo.html#text-date
3142 It's too dangerous (or too complicated in the case of "eval"). We do
3143 not want to have such things in the core.
3146 ``encoding`` Directive
3147 ======================
3149 Add an "encoding" directive to specify the character encoding of the
3150 input data? Not a good idea for the following reasons:
3152 - When it sees the directive, the parser will already have read the
3153 input data, and encoding determination will already have been done.
3155 - If a file with an "encoding" directive is edited and saved with
3156 a different encoding, the directive may cause data corruption.
3159 Support for Annotations
3160 =======================
3162 Add an "annotation" role, as the equivalent of the HTML "title"
3163 attribute? This is secondary information that may "pop up" when the
3164 pointer hovers over the main text. A corresponding directive would be
3165 required to associate annotations with the original text (by name, or
3166 positionally as in anonymous targets?).
3168 There have not been many requests for such feature, though. Also,
3169 cluttering WYSIWYG plaintext with annotations may not seem like a good
3170 idea, and there is no "tool tip" in formats other than HTML.
3176 Add a "term" role for unfamiliar or specialized terminology? Probably
3177 not; there is no real use case, and emphasis is enough for most cases.
3183 We need syntax for `object references`_.
3185 - Parameterized substitutions? For example::
3187 See |figure (figure name)| on |page (figure name)|.
3189 .. |figure (name)| figure-ref:: (name)
3190 .. |page (name)| page-ref:: (name)
3192 The result would be::
3194 See figure 3.11 on page 157.
3196 But this would require substitution directives to be processed at
3197 reference-time, not at definition-time as they are now. Or,
3198 perhaps the directives could just leave ``pending`` elements
3199 behind, and the transforms do the work? How to pass the data
3200 through? Too complicated. Use interpreted text roles.
3202 .. _object references:
3203 ../todo.html#object-numbering-and-object-references
3210 indent-tabs-mode: nil
3211 sentence-end-double-space: t