From c7a401dd1912c15056a4ad26b39887f662086bc9 Mon Sep 17 00:00:00 2001 From: Dave Love Date: Wed, 6 Dec 2000 20:48:43 +0000 Subject: [PATCH] Why no package system. Rationale for loading without effect. Defining compatibility aliases. --- lispref/tips.texi | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/lispref/tips.texi b/lispref/tips.texi index 3f428009519..031f6b41166 100644 --- a/lispref/tips.texi +++ b/lispref/tips.texi @@ -39,9 +39,10 @@ code intended for widespread use: @item Since all global variables share the same name space, and all functions share another name space, you should choose a short word to distinguish -your program from other Lisp programs. Then take care to begin the -names of all global variables, constants, and functions with the chosen -prefix. This helps avoid name conflicts. +your program from other Lisp programs.@footnote{The benefits of a Common +Lisp-style package system are considered not to outweigh the costs.} +Then take care to begin the names of all global variables, constants, +and functions with the chosen prefix. This helps avoid name conflicts. This recommendation applies even to names for traditional Lisp primitives that are not primitives in Emacs Lisp---even to @@ -186,6 +187,8 @@ shift key held down. These events include @kbd{S-mouse-1}, users. @item +@cindex mouse-2 +@cindex references, following Special major modes used for read-only text should usually redefine @kbd{mouse-2} and @key{RET} to trace some sort of reference in the text. Modes such as Dired, Info, Compilation, and Occur redefine it in this @@ -197,13 +200,29 @@ good to include a command to enable and disable the feature, Provide a command named @code{@var{whatever}-mode} which turns the feature on or off, and make it autoload (@pxref{Autoload}). Design the package so that simply loading it has no visible effect---that should not enable -the feature. Users will request the feature by invoking the command. +the feature.@footnote{Consider that the package may be loaded +arbitrarily by Custom for instance.} Users will request the feature by +invoking the command. @item It is a bad idea to define aliases for the Emacs primitives. Use the standard names instead. @item +If a package needs to define an alias or a new function for +compatibility with some other version of Emacs, name if with the package +prefix, not with the raw name with which it occurs in the other version. +Here is an example from Gnus, which provides many examples of such +compatibility issues. + +@example +(defalias 'gnus-point-at-bol + (if (fboundp 'point-at-bol) + 'point-at-bol + 'line-beginning-position)) +@end example + +@item Redefining (or advising) an Emacs primitive is discouraged. It may do the right thing for a particular program, but there is no telling what other programs might break as a result. -- 2.11.4.GIT