pike.git/ src/ operators.c

2003-01-15

2003-01-15 13:08:11 by Johan Sundström <oyasumi@gmail.com>

• b8d9a08e2c2c6be806f79432980a57442f3ca9d7 (33 lines) (+31/-2) ^{[ Show | Annotate ]}
  Branch: 7.9

Added a lightly edited excerpt to the refdocs of a good discussion on `/ and `% by Niels Möller on the Pike list. It would probably be good to get some more eyes on it to ensure that I didn't get anything wrong.

Rev: src/operators.c:1.169

2:   || This file is part of Pike. For copyright information see COPYRIGHT.   || Pike is distributed under GPL, LGPL and MPL. See the file COPYING   || for more information. - || $Id: operators.c,v 1.168 2002/12/30 12:46:50 grubba Exp $ + || $Id: operators.c,v 1.169 2003/01/15 13:08:11 jhs Exp $   */      #include "global.h"   #include <math.h> - RCSID("$Id: operators.c,v 1.168 2002/12/30 12:46:50 grubba Exp $"); + RCSID("$Id: operators.c,v 1.169 2003/01/15 13:08:11 jhs Exp $");   #include "interpret.h"   #include "svalue.h"   #include "multiset.h"
2663:    *! are int, the result will be truncated to an int. Otherwise the    *! result will be a float.    *! @endmixed +  *! @note +  *! Unlike in some languages, the function f(x) = x/n behaves in a +  *! well-defined, sane way. When you increase x, f(x) will jump one step +  *! for each n:th increment. For all x, (x + n) / n = x/n + 1; crossing +  *! zero is not special. This also means that / and % are compatible, so +  *! that a = b*(a/b) + a%b for all a and b. +  *! @seealso +  *! @[`%]    */   PMOD_EXPORT void f_divide(INT32 args)   {
2834:    *! The result will be a float if either @[arg1] or @[arg2] is    *! a float, and an int otherwise.    *! @endmixed +  *! +  *! For numbers, this means that +  *! @ol +  *! @item +  *! a % b always has the same sign as b (typically b is positive; +  *! array size, rsa modulo, etc, and a varies a lot more than b). +  *! @item +  *! The function f(x) = x % n behaves in a sane way; as x increases, +  *! f(x) cycles through the values 0,1, ..., n-1, 0, .... Nothing +  *! strange happens when you cross zero. +  *! @item +  *! The % operator implements the binary "mod" operation, as defined +  *! by Donald Knuth (see the Art of Computer Programming, 1.2.4). It +  *! should be noted that Pike treats %-by-0 as an error rather than +  *! returning 0, though. +  *! @item +  *! / and % are compatible, so that a = b*(a/b) + a%b for all a and b. +  *! @endol +  *! @seealso +  *! @[`/]    */   PMOD_EXPORT void f_mod(INT32 args)   {