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36 .\" @(#)bc.1 6.8 (Berkeley) 8/8/91
37 .\"
38 .Dd November 14, 2009
39 .Dt BC 1
40 .Os
41 .Sh NAME
42 .Nm bc
43 .Nd arbitrary-precision arithmetic language and calculator
44 .Sh SYNOPSIS
45 .Nm
46 .Op Fl cl
47 .Op Fl e Ar expression
48 .Op Ar file ...
49 .Sh DESCRIPTION
50 .Nm
51 is an interactive processor for a language which resembles
52 C but provides unlimited precision arithmetic.
53 It takes input from any expressions on the command line and
54 any files given, then reads the standard input.
55 .Pp
56 Options available:
57 .Bl -tag -width Ds
58 .It Fl c
59 .Nm
60 is actually a preprocessor for
61 .Xr dc 1 ,
62 which it invokes automatically, unless the
63 .Fl c
64 .Pq compile only
65 option is present.
66 In this case the generated
67 .Xr dc 1
68 instructions are sent to the standard output,
69 instead of being interpreted by a running
70 .Xr dc 1
71 process.
72 .It Fl e Ar expression
73 Evaluate
74 .Ar expression .
75 If multiple
76 .Fl e
77 options are specified, they are processed in the order given,
78 separated by newlines.
79 .It Fl l
80 Allow specification of an arbitrary precision math library.
81 The definitions in the library are available to command line
82 expressions.
83 .El
84 .Pp
85 The syntax for
86 .Nm
87 programs is as follows:
88 .Sq L
89 means letter a-z;
90 .Sq E
91 means expression;
92 .Sq S
93 means statement.
94 As a non-portable extension, it is possible to use long names
95 in addition to single letter names.
96 A long name is a sequence starting with a lowercase letter
97 followed by any number of lowercase letters and digits.
98 The underscore character
99 .Pq Sq _
100 counts as a letter.
101 .Pp
102 Comments
103 .Bd -unfilled -offset indent -compact
104 are enclosed in /* and */
105 are enclosed in # and the next newline
106 .Ed
107 .Pp
108 The newline is not part of the line comment,
109 which in itself is a non-portable extension.
110 .Pp
111 Names
112 .Bd -unfilled -offset indent -compact
113 simple variables: L
114 array elements: L [ E ]
115 The words `ibase', `obase', and `scale'
116 The word `last' or a single dot
117 .Ed
118 .Pp
119 Other operands
120 .Bd -unfilled -offset indent -compact
121 arbitrarily long numbers with optional sign and decimal point
122 ( E )
123 sqrt ( E )
124 length ( E ) number of significant decimal digits
125 scale ( E ) number of digits right of decimal point
126 L ( E , ... , E )
127 .Ed
128 .Pp
129 The sequence
130 .Sq \e<newline><whitespace>
131 is ignored within numbers.
132 .Pp
133 Operators
134 .Pp
135 The following arithmetic and logical operators can be used.
136 The semantics of the operators is the same as in the C language.
137 They are listed in order of decreasing precedence.
138 Operators in the same group have the same precedence.
139 .Bl -column "= += \-= *= /= %= ^=" "Associativity" "multiply, divide, modulus" -offset indent
140 .It Sy "Operator" Ta Sy "Associativity" Ta Sy "Description"
141 .It "++ \-\-" Ta "none" Ta "increment, decrement"
142 .It "\-" Ta "none" Ta "unary minus"
143 .It "^" Ta "right" Ta "power"
144 .It "* / %" Ta "left" Ta "multiply, divide, modulus"
145 .It "+ \-" Ta "left" Ta "plus, minus"
146 .It "= += -= *= /= %= ^=" Ta "right" Ta "assignment"
147 .It "== <= >= != < >" Ta "none" Ta "relational"
148 .It "!" Ta "none" Ta "boolean not"
149 .It "&&" Ta "left" Ta "boolean and"
150 .It "||" Ta "left" Ta "boolean or"
151 .El
152 .Pp
153 Note the following:
154 .Bl -bullet -offset indent
155 .It
156 The relational operators may appear in any expression.
157 The
158 .St -p1003.2
159 standard only allows them in the conditional expression of an
160 .Sq if ,
161 .Sq while
162 or
163 .Sq for
164 statement.
165 .It
166 The relational operators have a lower precedence than the assignment
167 operators.
168 This has the consequence that the expression
169 .Sy a = b < c
170 is interpreted as
171 .Sy (a = b) < c ,
172 which is probably not what the programmer intended.
173 .It
174 In contrast with the C language, the relational operators all have
175 the same precedence, and are non-associative.
176 The expression
177 .Sy a < b < c
178 will produce a syntax error.
179 .It
180 The boolean operators (!, && and ||) are non-portable extensions.
181 .It
182 The boolean not
183 (!) operator has much lower precedence than the same operator in the
184 C language.
185 This has the consequence that the expression
186 .Sy !a < b
187 is interpreted as
188 .Sy !(a < b) .
189 Prudent programmers use parentheses when writing expressions involving
190 boolean operators.
191 .El
192 .Pp
193 Statements
194 .Bd -unfilled -offset indent -compact
195 E
196 { S ; ... ; S }
197 if ( E ) S
198 if ( E ) S else S
199 while ( E ) S
200 for ( E ; E ; E ) S
201 null statement
202 break
203 continue
204 quit
205 a string of characters, enclosed in double quotes
206 print E ,..., E
207 .Ed
208 .Pp
209 A string may contain any character, except a double quote.
210 The if statement with an else branch is a non-portable extension.
211 All three E's in a for statement may be empty.
212 This is a non-portable extension.
213 The continue and print statements are also non-portable extensions.
214 .Pp
215 The print statement takes a list of comma-separated expressions.
216 Each expression in the list is evaluated and the computed
217 value is printed and assigned to the variable `last'.
218 No trailing newline is printed.
219 The expression may also be a string enclosed in double quotes.
220 Within these strings the following escape sequences may be used:
221 .Sq \ea
222 for bell (alert),
223 .Sq \eb
224 for backspace,
225 .Sq \ef
226 for formfeed,
227 .Sq \en
228 for newline,
229 .Sq \er
230 for carriage return,
231 .Sq \et
232 for tab,
233 .Sq \eq
234 for double quote and
235 .Sq \e\e
236 for backslash.
237 Any other character following a backslash will be ignored.
238 Strings will not be assigned to `last'.
239 .Pp
240 Function definitions
241 .Bd -unfilled -offset indent
242 define L ( L ,..., L ) {
243 auto L, ... , L
244 S; ... S
245 return ( E )
246 }
247 .Ed
248 .Pp
249 As a non-portable extension, the opening brace of the define statement
250 may appear on the next line.
251 The return statement may also appear in the following forms:
252 .Bd -unfilled -offset indent
253 return
254 return ()
255 return E
256 .Ed
257 .Pp
258 The first two are equivalent to the statement
259 .Dq return 0 .
260 The last form is a non-portable extension.
261 Not specifying a return statement is equivalent to writing
262 .Dq return (0) .
263 .Pp
264 Functions available in the math library, which is loaded by specifying the
265 .Fl l
266 flag on the command line
267 .Pp
268 .Bl -tag -width j(n,x) -offset indent -compact
269 .It s(x)
270 sine
271 .It c(x)
272 cosine
273 .It e(x)
274 exponential
275 .It l(x)
276 log
277 .It a(x)
278 arctangent
279 .It j(n,x)
280 Bessel function
281 .El
282 .Pp
283 All function arguments are passed by value.
284 .Pp
285 The value of a statement that is an expression is printed
286 unless the main operator is an assignment.
287 The value printed is assigned to the special variable `last'.
288 This is a non-portable extension.
289 A single dot may be used as a synonym for `last'.
290 Either semicolons or newlines may separate statements.
291 Assignment to
292 .Ar scale
293 influences the number of digits to be retained on arithmetic
294 operations in the manner of
295 .Xr dc 1 .
296 Assignments to
297 .Ar ibase
298 or
299 .Ar obase
300 set the input and output number radix respectively.
301 .Pp
302 The same letter may be used as an array, a function,
303 and a simple variable simultaneously.
304 All variables are global to the program.
305 `Auto' variables are pushed down during function calls.
306 When using arrays as function arguments
307 or defining them as automatic variables,
308 empty square brackets must follow the array name.
309 .Pp
310 For example
311 .Bd -literal -offset indent
312 scale = 20
313 define e(x){
314 auto a, b, c, i, s
315 a = 1
316 b = 1
317 s = 1
318 for(i=1; 1==1; i++){
319 a = a*x
320 b = b*i
321 c = a/b
322 if(c == 0) return(s)
323 s = s+c
324 }
325 }
326 .Ed
327 .Pp
328 defines a function to compute an approximate value of
329 the exponential function and
330 .Pp
331 .Dl for(i=1; i<=10; i++) e(i)
332 .Pp
333 prints approximate values of the exponential function of
334 the first ten integers.
335 .Bd -literal -offset indent
336 $ bc -l -e 'scale = 500; 2 * a(2^10000)' -e quit
337 .Ed
338 prints an approximation of pi.
339 .Sh FILES
340 .Bl -tag -width /usr/share/misc/bc.library -compact
341 .It Pa /usr/share/misc/bc.library
342 math library, read when the
343 .Fl l
344 option is specified on the command line.
345 .El
346 .Sh SEE ALSO
347 .Xr dc 1
348 .Rs
349 .%A "Lorinda Cherry"
350 .%A "Robert Morris"
351 .%B "4.4BSD Users's Supplementary Documents (USD)"
352 .%T "BC \- An Arbitrary Precision Desk-Calculator Language"
353 .Re
354 .\" .Pa /usr/share/doc/usd/06.bc/ .
355 .Sh STANDARDS
356 The
357 .Nm
358 utility is compliant with the
359 .St -p1003.1-2004
360 specification.
361 .Pp
362 The flags
363 .Op Fl ce
364 are extensions to that specification.
365 .Sh HISTORY
366 The
367 .Nm
368 command first appeared in
369 .At v6 .
370 A complete rewrite of the
371 .Nm
372 command first appeared in
373 .Ox 3.5 .
374 .Sh AUTHORS
375 .An -nosplit
376 The original version of the
377 .Nm
378 command was written by
379 .An Robert Morris
380 and
381 .An Lorinda Cherry .
382 The current version of the
383 .Nm
384 utility was written by
385 .An Otto Moerbeek .
386 .Sh BUGS
387 .Ql Quit
388 is interpreted when read, not when executed.
389 .Pp
390 Some non-portable extensions, as found in the GNU version of the
391 .Nm
392 utility are not implemented (yet).