Annotation of src/usr.bin/dc/dc.1, Revision 1.15
1.15 ! otto 1: .\" $OpenBSD: dc.1,v 1.14 2003/11/04 08:10:06 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.
1.15 ! otto 137: .It Ic a
! 138: Pop the top value from the stack.
! 139: If that value is a number, compute the integer part of the number modulo 256.
! 140: If the result is zero, push an empty string.
! 141: Otherwise push a one character string by interpreting the computed value
! 142: as an
! 143: .Tn ASCII
! 144: character.
! 145: .Pp
! 146: If the top value is a string, push a string containing the first character
! 147: of the original string.
! 148: If the original string is empty, an empty string is pushed back.
! 149: The
! 150: .Ic a
! 151: operator is a non-portable extension.
1.10 otto 152: .It Ic c
153: All values on the stack are popped.
154: .It Ic d
155: The top value on the stack is duplicated.
156: .It Ic f
157: All values on the stack are printed, separated by newlines.
158: .It Ic i
159: The top value on the stack is popped and used as the
160: base for further input.
161: The initial input base is 10.
162: .It Ic I
163: Pushes the input base on the top of the stack.
164: .It Ic J
1.15 ! otto 165: Pop the top value from the stack.
1.10 otto 166: The recursion level is popped by that value and, following that,
167: the input is skipped until the first occurrence of the
168: .Ic M
169: operator.
1.1 otto 170: The
1.10 otto 171: .Ic J
1.15 ! otto 172: operator is a non-portable extension, used by the
1.10 otto 173: .Xr bc 1
174: command.
175: .It Ic K
176: The current scale factor is pushed onto the stack.
177: .It Ic k
178: The top of the stack is popped, and that value is used as
179: a non-negative scale factor:
180: the appropriate number of places
181: are printed on output,
182: and maintained during multiplication, division, and exponentiation.
183: The interaction of scale factor,
184: input base, and output base will be reasonable if all are changed
185: together.
186: .It Ic L Ns Ar x
187: Register
1.1 otto 188: .Ar x
1.10 otto 189: is treated as a stack and its top value is popped onto the main stack.
1.1 otto 190: .It Ic l Ns Ar x
191: The
192: value in register
193: .Ar x
194: is pushed on the stack.
195: The register
196: .Ar x
197: is not altered.
1.4 otto 198: Initially, all registers contain the value zero.
1.10 otto 199: .It Ic M
200: Mark used by the
201: .Ic J
202: operator.
203: The
204: .Ic M
205: operator is a non-portable extensions, used by the
206: .Xr bc 1
207: command.
1.15 ! otto 208: .It Ic n
! 209: The top value on the stack is popped and printed without a newline.
! 210: This is a non-portable extension.
1.10 otto 211: .It Ic O
212: Pushes the output base on the top of the stack.
213: .It Ic o
214: The top value on the stack is popped and used as the
215: base for further output.
216: The initial output base is 10.
1.1 otto 217: .It Ic P
218: The top of the stack is popped.
1.2 jmc 219: If the top of the stack is a string, it is printed without a trailing newline.
1.1 otto 220: If the top of the stack is a number, it is interpreted as a
221: base 256 number, and each digit of this base 256 number is printed as
222: an
223: .Tn ASCII
224: character, without a trailing newline.
1.10 otto 225: .It Ic p
226: The top value on the stack is printed with a trailing newline.
227: The top value remains unchanged.
228: .It Ic Q
229: The top value on the stack is popped and the string execution level is popped
230: by that value.
1.1 otto 231: .It Ic q
232: Exits the program.
233: If executing a string, the recursion level is
234: popped by two.
1.14 otto 235: .It Ic r
236: The top two values on the stack are reversed (swapped).
237: This is a non-portable extension.
1.10 otto 238: .It Ic S Ns Ar x
239: Register
240: .Ar x
241: is treated as a stack.
242: The top value of the main stack is popped and pushed on it.
243: .It Ic s Ns Ar x
244: The
245: top of the stack is popped and stored into
246: a register named
247: .Ar x ,
248: where
249: .Ar x
250: may be any character, including space, tab or any other special character.
251: .It Ic v
252: Replaces the top element on the stack by its square root.
253: The scale of the result is the maximum of the scale of the argument
254: and the current value of scale.
255: .It Ic X
256: Replaces the number on the top of the stack with its scale factor.
257: If the top of the stack is a string, replace it with the integer 0.
1.1 otto 258: .It Ic x
259: Treats the top element of the stack as a character string
260: and executes it as a string of
261: .Nm
262: commands.
1.10 otto 263: .It Ic Z
264: Replaces the number on the top of the stack with its length.
265: The length of a string is its number of characters.
266: The length of a number is its number of digits, not counting the minus sign
267: and decimal point.
268: .It Ic z
269: The stack level is pushed onto the stack.
1.1 otto 270: .It Cm [ Ns ... Ns Cm ]
271: Puts the bracketed
272: .Tn ASCII
273: string onto the top of the stack.
1.5 otto 274: If the string includes brackets, these must be properly balanced.
1.6 jmc 275: The backslash character
276: .Pq Sq \e
277: may be used as an escape character, making it
1.5 otto 278: possible to include unbalanced brackets in strings.
1.6 jmc 279: To include a backslash in a string, use a double backslash.
1.1 otto 280: .It Xo
281: .Cm < Ns Va x
282: .Cm > Ns Va x
283: .Cm = Ns Va x
284: .Cm !< Ns Va x
285: .Cm !> Ns Va x
286: .Cm != Ns Va x
287: .Xc
288: The top two elements of the stack are popped and compared.
289: Register
290: .Ar x
291: is executed if they obey the stated
292: relation.
1.12 otto 293: .It Xo
294: .Cm < Ns Va x Ns e Ns Va y
295: .Cm > Ns Va x Ns e Ns Va y
296: .Cm = Ns Va x Ns e Ns Va y
297: .Cm !< Ns Va x Ns e Ns Va y
298: .Cm !> Ns Va x Ns e Ns Va y
299: .Cm != Ns Va x Ns e Ns Va y
300: .Xc
301: These operations are variants of the comparison operations above.
302: The first register name is followed by the letter
303: .Sq e
304: and another register name.
305: Register
306: .Ar x
307: will be executed if the relation is true, and register
308: .Ar y
309: will be executed if the relation is false.
310: This is a non-portable extension.
1.2 jmc 311: .It Ic \&!
1.1 otto 312: Interprets the rest of the line as a
313: .Ux
314: command.
1.2 jmc 315: .It Ic \&?
1.1 otto 316: A line of input is taken from the input source (usually the terminal)
317: and executed.
318: .It Ic : Ns Ar r
1.2 jmc 319: Pop two values from the stack.
320: The second value on the stack is stored into the array
1.1 otto 321: .Ar r
322: indexed by the top of stack.
323: .It Ic ; Ns Ar r
1.2 jmc 324: Pop a value from the stack.
325: The value is used as an index into register
1.1 otto 326: .Ar r .
327: The value in this register is pushed onto the stack.
328: .Pp
1.2 jmc 329: Array elements initially have the value zero.
1.1 otto 330: Each level of a stacked register has its own array associated with
331: it.
332: The command sequence
1.2 jmc 333: .Bd -literal -offset indent
1.1 otto 334: [first] 0:a [dummy] Sa [second] 0:a 0;a p La 0;a p
335: .Ed
336: .Pp
337: will print
1.2 jmc 338: .Bd -literal -offset indent
1.1 otto 339: second
340: first
341: .Ed
342: .Pp
343: since the string
344: .Ql second
345: is written in an array that is later popped, to reveal the array that
346: stored
347: .Ql first .
1.15 ! otto 348: .It Ic #
! 349: Skip the rest of the line.
! 350: This is a non-portable extension.
1.1 otto 351: .El
352: .Sh EXAMPLES
353: An example which prints the first ten values of
1.2 jmc 354: .Ic n! :
355: .Bd -literal -offset indent
1.1 otto 356: [la1+dsa*pla10>y]sy
357: 0sa1
358: lyx
359: .Ed
360: .Pp
361: Independent of the current input base, the command
1.2 jmc 362: .Bd -literal -offset indent
1.1 otto 363: Ai
364: .Ed
365: .Pp
366: will reset the input base to decimal 10.
367: .Sh DIAGNOSTICS
1.2 jmc 368: .Bl -diag
369: .It %c (0%o) is unimplemented
1.1 otto 370: an undefined operation was called.
1.2 jmc 371: .It stack empty
1.1 otto 372: for not enough elements on the stack to do what was asked.
1.2 jmc 373: .It stack register '%c' (0%o) is empty
374: for an
1.1 otto 375: .Ar L
376: operation from a stack register that is empty.
1.2 jmc 377: .It Runtime warning: non-zero scale in exponent
1.1 otto 378: for a fractional part of an exponent that is being ignored.
1.2 jmc 379: .It divide by zero
1.1 otto 380: for trying to divide by zero.
1.2 jmc 381: .It remainder by zero
1.1 otto 382: for trying to take a remainder by zero.
1.2 jmc 383: .It square root of negative number
1.1 otto 384: for trying to take the square root of a negative number.
1.2 jmc 385: .It index too big
1.1 otto 386: for an array index that is larger than 2048.
1.2 jmc 387: .It negative index
1.1 otto 388: for a negative array index.
1.13 jmc 389: .It "input base must be a number between 2 and 16"
1.1 otto 390: for trying to set an illegal input base.
1.2 jmc 391: .It output base must be a number greater than 1
1.1 otto 392: for trying to set an illegal input base.
1.2 jmc 393: .It scale must be a nonnegative number
1.1 otto 394: for trying to set a negative or zero scale.
1.2 jmc 395: .It scale too large
1.1 otto 396: for trying to set a scale that is too large.
1.2 jmc 397: A scale must be representable as a 32-bit unsigned number.
398: .It Q command argument exceeded string execution depth
1.1 otto 399: for trying to pop the recursion level more than the current
400: recursion level.
1.2 jmc 401: .It Q command requires a number >= 1
1.1 otto 402: for trying to pop an illegal number of recursion levels.
1.2 jmc 403: .It recursion too deep
1.1 otto 404: for too many levels of nested execution.
405: .Pp
406: The recursion level is increased by one if the
407: .Ar x
408: or
1.2 jmc 409: .Ar ?\&
1.1 otto 410: operation or one of the compare operations resulting in the execution
411: of register is executed.
412: As an exception, the recursion level is not increased if the operation
413: is executed as the last command of a string.
1.2 jmc 414: For example, the commands
415: .Bd -literal -offset indent
1.1 otto 416: [lax]sa
417: 1 lax
418: .Ed
419: .Pp
420: will execute an endless loop, while the commands
1.2 jmc 421: .Bd -literal -offset indent
1.1 otto 422: [laxp]sa
423: 1 lax
424: .Ed
425: .Pp
426: will terminate because of a too deep recursion level.
1.8 otto 427: .It J command argument exceeded string execution depth
428: for trying to pop the recursion level more than the current
429: recursion level.
430: .It mark not found
1.9 jmc 431: for a failed scan for an occurrence of the
1.8 otto 432: .Ic M
433: operator.
1.1 otto 434: .El
435: .Sh SEE ALSO
1.2 jmc 436: .Xr bc 1
1.1 otto 437: .Pp
438: USD:05
439: .Em "DC \- An Interactive Desk Calculator"
440: .Sh STANDARDS
441: The arithmetic operations of the
442: .Nm
443: utility are expected to conform to the definition listed in the
444: .Xr bc 1
445: section of the
446: .St -p1003.2
447: specification.
448: .Sh HISTORY
449: The
450: .Nm
451: command first appeared in
452: .At v6 .
453: A complete rewrite of the
454: .Nm
455: command using the
456: .Xr bn 3
457: big number routines first appeared in
458: .Ox 3.5 .
459: .Sh AUTHORS
460: The original version of the
461: .Nm
462: command was written by
463: .An Robert Morris
464: and
465: .An Lorinda Cherry .
466: The current version of the
467: .Nm
468: utility was written by
469: .An Otto Moerbeek .
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