Annotation of src/usr.bin/dc/dc.1, Revision 1.9
1.9 ! jmc 1: .\" $OpenBSD: dc.1,v 1.8 2003/10/18 19:47:10 otto Exp $
1.1 otto 2: .\"
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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.
116: For exponentation 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.
1.1 otto 137: .It Ic s Ns Ar x
138: The
139: top of the stack is popped and stored into
140: a register named
141: .Ar x ,
142: where
143: .Ar x
144: may be any character, including space, tab or any other special character.
145: If the
1.8 otto 146: .Ic s
1.1 otto 147: is capitalized,
148: .Ar x
149: is treated as a stack and the value is pushed on it.
150: .It Ic l Ns Ar x
151: The
152: value in register
153: .Ar x
154: is pushed on the stack.
155: The register
156: .Ar x
157: is not altered.
1.4 otto 158: Initially, all registers contain the value zero.
1.1 otto 159: If the
160: .Ar l
161: is capitalized,
162: register
163: .Ar x
164: is treated as a stack and its top value is popped onto the main stack.
165: .It Ic d
166: The top value on the stack is duplicated.
167: .It Ic p
168: The top value on the stack is printed with a trailing newline.
169: The top value remains unchanged.
170: .It Ic P
171: The top of the stack is popped.
1.2 jmc 172: If the top of the stack is a string, it is printed without a trailing newline.
1.1 otto 173: If the top of the stack is a number, it is interpreted as a
174: base 256 number, and each digit of this base 256 number is printed as
175: an
176: .Tn ASCII
177: character, without a trailing newline.
178: .It Ic f
179: All values on the stack are printed, separated by newlines.
180: .It Ic q
181: Exits the program.
182: If executing a string, the recursion level is
183: popped by two.
184: If
1.8 otto 185: .Ic q
1.1 otto 186: is capitalized,
187: the top value on the stack is popped and the string execution level is popped
188: by that value.
189: .It Ic x
190: Treats the top element of the stack as a character string
191: and executes it as a string of
192: .Nm
193: commands.
194: .It Ic X
1.2 jmc 195: Replaces the number on the top of the stack with its scale factor.
196: If the top of the stack is a string, replace it with the integer 0.
1.1 otto 197: .It Cm [ Ns ... Ns Cm ]
198: Puts the bracketed
199: .Tn ASCII
200: string onto the top of the stack.
1.5 otto 201: If the string includes brackets, these must be properly balanced.
1.6 jmc 202: The backslash character
203: .Pq Sq \e
204: may be used as an escape character, making it
1.5 otto 205: possible to include unbalanced brackets in strings.
1.6 jmc 206: To include a backslash in a string, use a double backslash.
1.1 otto 207: .It Xo
208: .Cm < Ns Va x
209: .Cm > Ns Va x
210: .Cm = Ns Va x
211: .Cm !< Ns Va x
212: .Cm !> Ns Va x
213: .Cm != Ns Va x
214: .Xc
215: The top two elements of the stack are popped and compared.
216: Register
217: .Ar x
218: is executed if they obey the stated
219: relation.
220: .It Ic v
221: Replaces the top element on the stack by its square root.
222: The scale of the result is the maximum of the scale of the argument
223: and the current value of scale.
1.2 jmc 224: .It Ic \&!
1.1 otto 225: Interprets the rest of the line as a
226: .Ux
227: command.
228: .It Ic c
229: All values on the stack are popped.
230: .It Ic i
231: The top value on the stack is popped and used as the
1.2 jmc 232: base for further input.
233: The initial input base is 10.
1.1 otto 234: .Ic I
235: Pushes the input base on the top of the stack.
236: .It Ic o
237: The top value on the stack is popped and used as the
1.2 jmc 238: base for further output.
239: The initial output base is 10.
1.1 otto 240: .It Ic O
241: Pushes the output base on the top of the stack.
242: .It Ic k
243: The top of the stack is popped, and that value is used as
244: a non-negative scale factor:
245: the appropriate number of places
246: are printed on output,
247: and maintained during multiplication, division, and exponentiation.
248: The interaction of scale factor,
249: input base, and output base will be reasonable if all are changed
250: together.
251: .It Ic K
252: The current scale factor is pushed onto the stack.
253: .It Ic z
254: The stack level is pushed onto the stack.
255: .It Ic Z
256: Replaces the number on the top of the stack with its length.
257: The length of a string is its number of characters.
258: The length of a number is its number of digits, not counting the minus sign
259: and decimal point.
1.2 jmc 260: .It Ic \&?
1.1 otto 261: A line of input is taken from the input source (usually the terminal)
262: and executed.
263: .It Ic : Ns Ar r
1.2 jmc 264: Pop two values from the stack.
265: The second value on the stack is stored into the array
1.1 otto 266: .Ar r
267: indexed by the top of stack.
268: .It Ic ; Ns Ar r
1.2 jmc 269: Pop a value from the stack.
270: The value is used as an index into register
1.1 otto 271: .Ar r .
272: The value in this register is pushed onto the stack.
273: .Pp
1.2 jmc 274: Array elements initially have the value zero.
1.1 otto 275: Each level of a stacked register has its own array associated with
276: it.
277: The command sequence
1.2 jmc 278: .Bd -literal -offset indent
1.1 otto 279: [first] 0:a [dummy] Sa [second] 0:a 0;a p La 0;a p
280: .Ed
281: .Pp
282: will print
1.2 jmc 283: .Bd -literal -offset indent
1.1 otto 284: second
285: first
286: .Ed
287: .Pp
288: since the string
289: .Ql second
290: is written in an array that is later popped, to reveal the array that
291: stored
292: .Ql first .
1.8 otto 293: .It Ic J
1.9 ! jmc 294: Pop the top value of the stack.
! 295: The recursion level is popped by that value and, following that,
! 296: the input is skipped until the first occurrence of the
1.8 otto 297: .Ic M
298: operator.
299: .It Ic M
300: Mark used by the
301: .Ic J
302: operator.
303: The
304: .Ic J
305: and
306: .Ic M
307: operators are non-portable extensions, used by the
308: .Xr bc 1
309: command.
1.1 otto 310: .El
311: .Sh EXAMPLES
312: An example which prints the first ten values of
1.2 jmc 313: .Ic n! :
314: .Bd -literal -offset indent
1.1 otto 315: [la1+dsa*pla10>y]sy
316: 0sa1
317: lyx
318: .Ed
319: .Pp
320: Independent of the current input base, the command
1.2 jmc 321: .Bd -literal -offset indent
1.1 otto 322: Ai
323: .Ed
324: .Pp
325: will reset the input base to decimal 10.
326: .Sh DIAGNOSTICS
1.2 jmc 327: .Bl -diag
328: .It %c (0%o) is unimplemented
1.1 otto 329: an undefined operation was called.
1.2 jmc 330: .It stack empty
1.1 otto 331: for not enough elements on the stack to do what was asked.
1.2 jmc 332: .It stack register '%c' (0%o) is empty
333: for an
1.1 otto 334: .Ar L
335: operation from a stack register that is empty.
1.2 jmc 336: .It Runtime warning: non-zero scale in exponent
1.1 otto 337: for a fractional part of an exponent that is being ignored.
1.2 jmc 338: .It divide by zero
1.1 otto 339: for trying to divide by zero.
1.2 jmc 340: .It remainder by zero
1.1 otto 341: for trying to take a remainder by zero.
1.2 jmc 342: .It square root of negative number
1.1 otto 343: for trying to take the square root of a negative number.
1.2 jmc 344: .It index too big
1.1 otto 345: for an array index that is larger than 2048.
1.2 jmc 346: .It negative index
1.1 otto 347: for a negative array index.
1.2 jmc 348: .It input base must be a number between 2 and 16
1.1 otto 349: for trying to set an illegal input base.
1.2 jmc 350: .It output base must be a number greater than 1
1.1 otto 351: for trying to set an illegal input base.
1.2 jmc 352: .It scale must be a nonnegative number
1.1 otto 353: for trying to set a negative or zero scale.
1.2 jmc 354: .It scale too large
1.1 otto 355: for trying to set a scale that is too large.
1.2 jmc 356: A scale must be representable as a 32-bit unsigned number.
357: .It Q command argument exceeded string execution depth
1.1 otto 358: for trying to pop the recursion level more than the current
359: recursion level.
1.2 jmc 360: .It Q command requires a number >= 1
1.1 otto 361: for trying to pop an illegal number of recursion levels.
1.2 jmc 362: .It recursion too deep
1.1 otto 363: for too many levels of nested execution.
364: .Pp
365: The recursion level is increased by one if the
366: .Ar x
367: or
1.2 jmc 368: .Ar ?\&
1.1 otto 369: operation or one of the compare operations resulting in the execution
370: of register is executed.
371: As an exception, the recursion level is not increased if the operation
372: is executed as the last command of a string.
1.2 jmc 373: For example, the commands
374: .Bd -literal -offset indent
1.1 otto 375: [lax]sa
376: 1 lax
377: .Ed
378: .Pp
379: will execute an endless loop, while the commands
1.2 jmc 380: .Bd -literal -offset indent
1.1 otto 381: [laxp]sa
382: 1 lax
383: .Ed
384: .Pp
385: will terminate because of a too deep recursion level.
1.8 otto 386: .It J command argument exceeded string execution depth
387: for trying to pop the recursion level more than the current
388: recursion level.
389: .It mark not found
1.9 ! jmc 390: for a failed scan for an occurrence of the
1.8 otto 391: .Ic M
392: operator.
1.1 otto 393: .El
394: .Sh SEE ALSO
1.2 jmc 395: .Xr bc 1
1.1 otto 396: .Pp
397: USD:05
398: .Em "DC \- An Interactive Desk Calculator"
399: .Sh STANDARDS
400: The arithmetic operations of the
401: .Nm
402: utility are expected to conform to the definition listed in the
403: .Xr bc 1
404: section of the
405: .St -p1003.2
406: specification.
407: .Sh HISTORY
408: The
409: .Nm
410: command first appeared in
411: .At v6 .
412: A complete rewrite of the
413: .Nm
414: command using the
415: .Xr bn 3
416: big number routines first appeared in
417: .Ox 3.5 .
418: .Sh AUTHORS
419: The original version of the
420: .Nm
421: command was written by
422: .An Robert Morris
423: and
424: .An Lorinda Cherry .
425: The current version of the
426: .Nm
427: utility was written by
428: .An Otto Moerbeek .
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