Annotation of src/usr.bin/dc/dc.1, Revision 1.13
1.13 ! jmc 1: .\" $OpenBSD: dc.1,v 1.12 2003/10/22 12:16:25 otto Exp $
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35: .\" @(#)dc.1 8.1 (Berkeley) 6/6/93
36: .\"
37: .Dd June 6, 1993
38: .Dt DC 1
39: .Sh NAME
40: .Nm dc
41: .Nd desk calculator
42: .Sh SYNOPSIS
43: .Nm
1.2 jmc 44: .Op Ar file
1.1 otto 45: .Sh DESCRIPTION
46: .Nm
47: is an arbitrary precision arithmetic package.
48: The overall structure of
49: .Nm
50: is
1.2 jmc 51: a stacking (reverse Polish) calculator i.e.\&
52: numbers are stored on a stack.
53: Adding a number pushes it onto the stack.
54: Arithmetic operations pop arguments off the stack
55: and push the results.
56: See also the
57: .Xr bc 1
58: utility, which is a preprocessor for
59: .Nm
60: providing infix notation and a C-like syntax
61: which implements functions and reasonable control
62: structures for programs.
63: .Pp
64: Ordinarily,
65: .Nm
66: operates on decimal integers,
67: but one may specify an input base, output base,
68: and a number of fractional digits (scale) to be maintained.
1.1 otto 69: If an argument is given,
70: input is taken from that file until its end,
71: then from the standard input.
1.2 jmc 72: Whitespace is ignored, expect where it signals the end of a number,
1.1 otto 73: end of a line or when a register name is expected.
74: The following constructions are recognized:
1.2 jmc 75: .Bl -tag -width "number"
1.1 otto 76: .It Va number
77: The value of the number is pushed on the stack.
78: A number is an unbroken string of the digits 0\-9 and letters A\-F.
1.2 jmc 79: It may be preceded by an underscore
80: .Pq Sq _
81: to input a negative number.
82: A number may contain a single decimal point.
1.1 otto 83: A number may also contain the characters A\-F, with the values 10\-15.
1.7 otto 84: .It Cm "+ - / * % ~ ^"
1.1 otto 85: The
86: top two values on the stack are added
87: (+),
88: subtracted
89: (\-),
90: multiplied (*),
91: divided (/),
92: remaindered (%),
1.7 otto 93: divided and remaindered (~),
1.1 otto 94: or exponentiated (^).
95: The two entries are popped off the stack;
96: the result is pushed on the stack in their place.
97: Any fractional part of an exponent is ignored.
98: .Pp
99: For addition and subtraction, the scale of the result is the maximum
100: of scales of the operands.
101: For division the scale of the result is defined
102: by the scale set by the
1.8 otto 103: .Ic k
1.1 otto 104: operation.
1.2 jmc 105: For multiplication, the scale is defined by the expression
106: .Sy min(a+b,max(a,b,scale)) ,
1.1 otto 107: where
108: .Sy a
109: and
110: .Sy b
111: are the scales of the operands, and
112: .Sy scale
1.2 jmc 113: is the scale defined by the
1.8 otto 114: .Ic k
1.1 otto 115: operation.
1.11 jmc 116: For exponentiation with a non-negative exponent, the scale of the result is
1.2 jmc 117: .Sy min(a*b,max(scale,a)) ,
1.1 otto 118: where
119: .Sy a
120: is the scale of the base, and
121: .Sy b
122: is the
123: .Em value
124: of the exponent.
125: If the exponent is negative, the scale of the result is the scale
126: defined by the
1.8 otto 127: .Ic k
1.1 otto 128: operation.
1.7 otto 129: .Pp
130: In the case of the division and modulus operator (~),
131: the resultant quotient is pushed first followed by the remainder.
132: This is a shorthand for the sequence:
133: .Bd -literal -offset indent -compact
134: x y / x y %
135: .Ed
136: The division and modulus operator is a non-portable extension.
1.10 otto 137: .It Ic c
138: All values on the stack are popped.
139: .It Ic d
140: The top value on the stack is duplicated.
141: .It Ic f
142: All values on the stack are printed, separated by newlines.
143: .It Ic i
144: The top value on the stack is popped and used as the
145: base for further input.
146: The initial input base is 10.
147: .It Ic I
148: Pushes the input base on the top of the stack.
149: .It Ic J
150: Pop the top value of the stack.
151: The recursion level is popped by that value and, following that,
152: the input is skipped until the first occurrence of the
153: .Ic M
154: operator.
1.1 otto 155: The
1.10 otto 156: .Ic J
157: operator is a non-portable extensions, used by the
158: .Xr bc 1
159: command.
160: .It Ic K
161: The current scale factor is pushed onto the stack.
162: .It Ic k
163: The top of the stack is popped, and that value is used as
164: a non-negative scale factor:
165: the appropriate number of places
166: are printed on output,
167: and maintained during multiplication, division, and exponentiation.
168: The interaction of scale factor,
169: input base, and output base will be reasonable if all are changed
170: together.
171: .It Ic L Ns Ar x
172: Register
1.1 otto 173: .Ar x
1.10 otto 174: is treated as a stack and its top value is popped onto the main stack.
1.1 otto 175: .It Ic l Ns Ar x
176: The
177: value in register
178: .Ar x
179: is pushed on the stack.
180: The register
181: .Ar x
182: is not altered.
1.4 otto 183: Initially, all registers contain the value zero.
1.10 otto 184: .It Ic M
185: Mark used by the
186: .Ic J
187: operator.
188: The
189: .Ic M
190: operator is a non-portable extensions, used by the
191: .Xr bc 1
192: command.
193: .It Ic O
194: Pushes the output base on the top of the stack.
195: .It Ic o
196: The top value on the stack is popped and used as the
197: base for further output.
198: The initial output base is 10.
1.1 otto 199: .It Ic P
200: The top of the stack is popped.
1.2 jmc 201: If the top of the stack is a string, it is printed without a trailing newline.
1.1 otto 202: If the top of the stack is a number, it is interpreted as a
203: base 256 number, and each digit of this base 256 number is printed as
204: an
205: .Tn ASCII
206: character, without a trailing newline.
1.10 otto 207: .It Ic p
208: The top value on the stack is printed with a trailing newline.
209: The top value remains unchanged.
210: .It Ic Q
211: The top value on the stack is popped and the string execution level is popped
212: by that value.
1.1 otto 213: .It Ic q
214: Exits the program.
215: If executing a string, the recursion level is
216: popped by two.
1.10 otto 217: .It Ic S Ns Ar x
218: Register
219: .Ar x
220: is treated as a stack.
221: The top value of the main stack is popped and pushed on it.
222: .It Ic s Ns Ar x
223: The
224: top of the stack is popped and stored into
225: a register named
226: .Ar x ,
227: where
228: .Ar x
229: may be any character, including space, tab or any other special character.
230: .It Ic v
231: Replaces the top element on the stack by its square root.
232: The scale of the result is the maximum of the scale of the argument
233: and the current value of scale.
234: .It Ic X
235: Replaces the number on the top of the stack with its scale factor.
236: If the top of the stack is a string, replace it with the integer 0.
1.1 otto 237: .It Ic x
238: Treats the top element of the stack as a character string
239: and executes it as a string of
240: .Nm
241: commands.
1.10 otto 242: .It Ic Z
243: Replaces the number on the top of the stack with its length.
244: The length of a string is its number of characters.
245: The length of a number is its number of digits, not counting the minus sign
246: and decimal point.
247: .It Ic z
248: The stack level is pushed onto the stack.
1.1 otto 249: .It Cm [ Ns ... Ns Cm ]
250: Puts the bracketed
251: .Tn ASCII
252: string onto the top of the stack.
1.5 otto 253: If the string includes brackets, these must be properly balanced.
1.6 jmc 254: The backslash character
255: .Pq Sq \e
256: may be used as an escape character, making it
1.5 otto 257: possible to include unbalanced brackets in strings.
1.6 jmc 258: To include a backslash in a string, use a double backslash.
1.1 otto 259: .It Xo
260: .Cm < Ns Va x
261: .Cm > Ns Va x
262: .Cm = Ns Va x
263: .Cm !< Ns Va x
264: .Cm !> Ns Va x
265: .Cm != Ns Va x
266: .Xc
267: The top two elements of the stack are popped and compared.
268: Register
269: .Ar x
270: is executed if they obey the stated
271: relation.
1.12 otto 272: .It Xo
273: .Cm < Ns Va x Ns e Ns Va y
274: .Cm > Ns Va x Ns e Ns Va y
275: .Cm = Ns Va x Ns e Ns Va y
276: .Cm !< Ns Va x Ns e Ns Va y
277: .Cm !> Ns Va x Ns e Ns Va y
278: .Cm != Ns Va x Ns e Ns Va y
279: .Xc
280: These operations are variants of the comparison operations above.
281: The first register name is followed by the letter
282: .Sq e
283: and another register name.
284: Register
285: .Ar x
286: will be executed if the relation is true, and register
287: .Ar y
288: will be executed if the relation is false.
289: This is a non-portable extension.
1.2 jmc 290: .It Ic \&!
1.1 otto 291: Interprets the rest of the line as a
292: .Ux
293: command.
1.2 jmc 294: .It Ic \&?
1.1 otto 295: A line of input is taken from the input source (usually the terminal)
296: and executed.
297: .It Ic : Ns Ar r
1.2 jmc 298: Pop two values from the stack.
299: The second value on the stack is stored into the array
1.1 otto 300: .Ar r
301: indexed by the top of stack.
302: .It Ic ; Ns Ar r
1.2 jmc 303: Pop a value from the stack.
304: The value is used as an index into register
1.1 otto 305: .Ar r .
306: The value in this register is pushed onto the stack.
307: .Pp
1.2 jmc 308: Array elements initially have the value zero.
1.1 otto 309: Each level of a stacked register has its own array associated with
310: it.
311: The command sequence
1.2 jmc 312: .Bd -literal -offset indent
1.1 otto 313: [first] 0:a [dummy] Sa [second] 0:a 0;a p La 0;a p
314: .Ed
315: .Pp
316: will print
1.2 jmc 317: .Bd -literal -offset indent
1.1 otto 318: second
319: first
320: .Ed
321: .Pp
322: since the string
323: .Ql second
324: is written in an array that is later popped, to reveal the array that
325: stored
326: .Ql first .
327: .El
328: .Sh EXAMPLES
329: An example which prints the first ten values of
1.2 jmc 330: .Ic n! :
331: .Bd -literal -offset indent
1.1 otto 332: [la1+dsa*pla10>y]sy
333: 0sa1
334: lyx
335: .Ed
336: .Pp
337: Independent of the current input base, the command
1.2 jmc 338: .Bd -literal -offset indent
1.1 otto 339: Ai
340: .Ed
341: .Pp
342: will reset the input base to decimal 10.
343: .Sh DIAGNOSTICS
1.2 jmc 344: .Bl -diag
345: .It %c (0%o) is unimplemented
1.1 otto 346: an undefined operation was called.
1.2 jmc 347: .It stack empty
1.1 otto 348: for not enough elements on the stack to do what was asked.
1.2 jmc 349: .It stack register '%c' (0%o) is empty
350: for an
1.1 otto 351: .Ar L
352: operation from a stack register that is empty.
1.2 jmc 353: .It Runtime warning: non-zero scale in exponent
1.1 otto 354: for a fractional part of an exponent that is being ignored.
1.2 jmc 355: .It divide by zero
1.1 otto 356: for trying to divide by zero.
1.2 jmc 357: .It remainder by zero
1.1 otto 358: for trying to take a remainder by zero.
1.2 jmc 359: .It square root of negative number
1.1 otto 360: for trying to take the square root of a negative number.
1.2 jmc 361: .It index too big
1.1 otto 362: for an array index that is larger than 2048.
1.2 jmc 363: .It negative index
1.1 otto 364: for a negative array index.
1.13 ! jmc 365: .It "input base must be a number between 2 and 16"
1.1 otto 366: for trying to set an illegal input base.
1.2 jmc 367: .It output base must be a number greater than 1
1.1 otto 368: for trying to set an illegal input base.
1.2 jmc 369: .It scale must be a nonnegative number
1.1 otto 370: for trying to set a negative or zero scale.
1.2 jmc 371: .It scale too large
1.1 otto 372: for trying to set a scale that is too large.
1.2 jmc 373: A scale must be representable as a 32-bit unsigned number.
374: .It Q command argument exceeded string execution depth
1.1 otto 375: for trying to pop the recursion level more than the current
376: recursion level.
1.2 jmc 377: .It Q command requires a number >= 1
1.1 otto 378: for trying to pop an illegal number of recursion levels.
1.2 jmc 379: .It recursion too deep
1.1 otto 380: for too many levels of nested execution.
381: .Pp
382: The recursion level is increased by one if the
383: .Ar x
384: or
1.2 jmc 385: .Ar ?\&
1.1 otto 386: operation or one of the compare operations resulting in the execution
387: of register is executed.
388: As an exception, the recursion level is not increased if the operation
389: is executed as the last command of a string.
1.2 jmc 390: For example, the commands
391: .Bd -literal -offset indent
1.1 otto 392: [lax]sa
393: 1 lax
394: .Ed
395: .Pp
396: will execute an endless loop, while the commands
1.2 jmc 397: .Bd -literal -offset indent
1.1 otto 398: [laxp]sa
399: 1 lax
400: .Ed
401: .Pp
402: will terminate because of a too deep recursion level.
1.8 otto 403: .It J command argument exceeded string execution depth
404: for trying to pop the recursion level more than the current
405: recursion level.
406: .It mark not found
1.9 jmc 407: for a failed scan for an occurrence of the
1.8 otto 408: .Ic M
409: operator.
1.1 otto 410: .El
411: .Sh SEE ALSO
1.2 jmc 412: .Xr bc 1
1.1 otto 413: .Pp
414: USD:05
415: .Em "DC \- An Interactive Desk Calculator"
416: .Sh STANDARDS
417: The arithmetic operations of the
418: .Nm
419: utility are expected to conform to the definition listed in the
420: .Xr bc 1
421: section of the
422: .St -p1003.2
423: specification.
424: .Sh HISTORY
425: The
426: .Nm
427: command first appeared in
428: .At v6 .
429: A complete rewrite of the
430: .Nm
431: command using the
432: .Xr bn 3
433: big number routines first appeared in
434: .Ox 3.5 .
435: .Sh AUTHORS
436: The original version of the
437: .Nm
438: command was written by
439: .An Robert Morris
440: and
441: .An Lorinda Cherry .
442: The current version of the
443: .Nm
444: utility was written by
445: .An Otto Moerbeek .
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