tbc.1 - plan9port - [fork] Plan 9 from user space
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---
tbc.1 (3758B)
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1 .TH BC 1
2 .SH NAME
3 bc \- arbitrary-precision arithmetic language
4 .SH SYNOPSIS
5 .B bc
6 [
7 .B -c
8 ]
9 [
10 .B -l
11 ]
12 [
13 .B -s
14 ]
15 [
16 .I file ...
17 ]
18 .SH DESCRIPTION
19 .I Bc
20 is an interactive processor for a language that resembles
21 C but provides arithmetic on numbers of arbitrary length with up
22 to 100 digits right of the decimal point.
23 It takes input from any files given, then reads
24 the standard input.
25 The
26 .B -l
27 argument stands for the name
28 of an arbitrary precision math library.
29 The
30 .B -s
31 argument suppresses the automatic display
32 of calculation results; all output is via the
33 .B print
34 command.
35 .PP
36 The following syntax for
37 .I bc
38 programs is like that of C;
39 .I L
40 means letter
41 .BR a - z ,
42 .I E
43 means expression,
44 .I S
45 means statement.
46 .TF length(E)
47 .TP
48 Lexical
49 .RS
50 .HP
51 comments are enclosed in
52 .B /* */
53 .HP
54 newlines end statements
55 .RE
56 .TP
57 Names
58 .IP
59 simple variables:
60 .I L
61 .br
62 array elements:
63 .IB L [ E ]
64 .br
65 The words
66 .BR ibase ,
67 .BR obase ,
68 and
69 .B scale
70 .TP
71 Other operands
72 .IP
73 arbitrarily long numbers with optional sign and decimal point.
74 .RS
75 .TP
76 .BI ( E )
77 .TP
78 .BI sqrt( E )
79 .TP
80 .BI length( E )
81 number of significant decimal digits
82 .TP
83 .BI scale( E )
84 number of digits right of decimal point
85 .TP
86 .IB L ( E , ... ,\fIE\fP)
87 function call
88 .RE
89 .TP
90 Operators
91 .RS
92 .HP
93 .B "+ - * / % ^\ "
94 .RB ( %
95 is remainder;
96 .B ^
97 is power)
98 .HP
99 .B "++ --\ "
100 .TP
101 .B "== <= >= != < >"
102 .TP
103 .B "= += -= *= /= %= ^="
104 .RE
105 .TP
106 Statements
107 .RS
108 .br
109 .I E
110 .br
111 .B {
112 .I S
113 .B ;
114 \&...
115 .B ;
116 .I S
117 .B }
118 .br
119 .B "print"
120 .I E
121 .br
122 .B "if ("
123 .I E
124 .B )
125 .I S
126 .br
127 .B "while ("
128 .I E
129 .B )
130 .I S
131 .br
132 .B "for ("
133 .I E
134 .B ;
135 .I E
136 .B ;
137 .I E
138 .B ")"
139 .I S
140 .br
141 null statement
142 .br
143 .B break
144 .br
145 .B quit
146 .br
147 \fL"\fRtext\fL"\fR
148 .RE
149 .TP
150 Function definitions
151 .RS
152 .br
153 .B define
154 .I L
155 .B (
156 .I L
157 .B ,
158 \&...
159 .B ,
160 .I L
161 .B ){
162 .PD0
163 .br
164 .B auto
165 .I L
166 .B ,
167 \&...
168 .B ,
169 .I L
170 .br
171 .I S
172 .B ;
173 \&...
174 .B ;
175 .I S
176 .br
177 .B return
178 .I E
179 .LP
180 .B }
181 .RE
182 .TP
183 Functions in
184 .B -l
185 math library
186 .RS
187 .TP
188 .BI s( x )
189 sine
190 .TP
191 .BI c( x )
192 cosine
193 .TP
194 .BI e( x )
195 exponential
196 .TP
197 .BI l( x )
198 log
199 .TP
200 .BI a( x )
201 arctangent
202 .TP
203 .BI j( "n, x" )
204 Bessel function
205 .RE
206 .PP
207 .DT
208 All function arguments are passed by value.
209 .PD
210 .PP
211 The value of an expression at the top level is printed
212 unless the main operator is an assignment or the
213 .B -s
214 command line argument is given.
215 Text in quotes, which may include newlines, is always printed.
216 Either semicolons or newlines may separate statements.
217 Assignment to
218 .B scale
219 influences the number of digits to be retained on arithmetic
220 operations in the manner of
221 .MR dc (1) .
222 Assignments to
223 .B ibase
224 or
225 .B obase
226 set the input and output number radix respectively.
227 .PP
228 The same letter may be used as an array, a function,
229 and a simple variable simultaneously.
230 All variables are global to the program.
231 Automatic variables are pushed down during function calls.
232 In a declaration of an array as a function argument
233 or automatic variable
234 empty square brackets must follow the array name.
235 .PP
236 .I Bc
237 is actually a preprocessor for
238 .MR dc (1) ,
239 which it invokes automatically, unless the
240 .B -c
241 (compile only)
242 option is present.
243 In this case the
244 .I dc
245 input is sent to the standard output instead.
246 .SH EXAMPLE
247 Define a function to compute an approximate value of
248 the exponential.
249 Use it to print 10 values.
250 (The exponential function in the library gives better answers.)
251 .PP
252 .EX
253 scale = 20
254 define e(x) {
255 auto a, b, c, i, s
256 a = 1
257 b = 1
258 s = 1
259 for(i=1; 1; i++) {
260 a *= x
261 b *= i
262 c = a/b
263 if(c == 0) return s
264 s += c
265 }
266 }
267 for(i=1; i<=10; i++) print e(i)
268 .EE
269 .SH FILES
270 .B \*9/lib/bclib
271 mathematical library
272 .SH SOURCE
273 .B \*9/src/cmd/bc.y
274 .SH "SEE ALSO"
275 .IR dc (1),
276 .MR hoc (1)
277 .SH BUGS
278 No
279 .LR && ,
280 .LR || ,
281 or
282 .L !
283 operators.
284 .PP
285 A
286 .L for
287 statement must have all three
288 .LR E s.
289 .PP
290 A
291 .L quit
292 is interpreted when read, not when executed.