| /* |
| FUNCTION |
| <<div>>---divide two integers |
| |
| INDEX |
| div |
| |
| ANSI_SYNOPSIS |
| #include <stdlib.h> |
| div_t div(int <[n]>, int <[d]>); |
| |
| TRAD_SYNOPSIS |
| #include <stdlib.h> |
| div_t div(<[n]>, <[d]>) |
| int <[n]>, <[d]>; |
| |
| DESCRIPTION |
| Divide |
| @tex |
| $n/d$, |
| @end tex |
| @ifnottex |
| <[n]>/<[d]>, |
| @end ifnottex |
| returning quotient and remainder as two integers in a structure <<div_t>>. |
| |
| RETURNS |
| The result is represented with the structure |
| |
| . typedef struct |
| . { |
| . int quot; |
| . int rem; |
| . } div_t; |
| |
| where the <<quot>> field represents the quotient, and <<rem>> the |
| remainder. For nonzero <[d]>, if `<<<[r]> = div(<[n]>,<[d]>);>>' then |
| <[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'. |
| |
| To divide <<long>> rather than <<int>> values, use the similar |
| function <<ldiv>>. |
| |
| PORTABILITY |
| <<div>> is ANSI. |
| |
| No supporting OS subroutines are required. |
| */ |
| |
| /* |
| * Copyright (c) 1990 Regents of the University of California. |
| * All rights reserved. |
| * |
| * This code is derived from software contributed to Berkeley by |
| * Chris Torek. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * This product includes software developed by the University of |
| * California, Berkeley and its contributors. |
| * 4. Neither the name of the University nor the names of its contributors |
| * may be used to endorse or promote products derived from this software |
| * without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include <_ansi.h> |
| #include <stdlib.h> /* div_t */ |
| |
| div_t |
| _DEFUN (div, (num, denom), |
| int num _AND |
| int denom) |
| { |
| div_t r; |
| |
| r.quot = num / denom; |
| r.rem = num % denom; |
| /* |
| * The ANSI standard says that |r.quot| <= |n/d|, where |
| * n/d is to be computed in infinite precision. In other |
| * words, we should always truncate the quotient towards |
| * 0, never -infinity or +infinity. |
| * |
| * Machine division and remainer may work either way when |
| * one or both of n or d is negative. If only one is |
| * negative and r.quot has been truncated towards -inf, |
| * r.rem will have the same sign as denom and the opposite |
| * sign of num; if both are negative and r.quot has been |
| * truncated towards -inf, r.rem will be positive (will |
| * have the opposite sign of num). These are considered |
| * `wrong'. |
| * |
| * If both are num and denom are positive, r will always |
| * be positive. |
| * |
| * This all boils down to: |
| * if num >= 0, but r.rem < 0, we got the wrong answer. |
| * In that case, to get the right answer, add 1 to r.quot and |
| * subtract denom from r.rem. |
| * if num < 0, but r.rem > 0, we also have the wrong answer. |
| * In this case, to get the right answer, subtract 1 from r.quot and |
| * add denom to r.rem. |
| */ |
| if (num >= 0 && r.rem < 0) { |
| ++r.quot; |
| r.rem -= denom; |
| } |
| else if (num < 0 && r.rem > 0) { |
| --r.quot; |
| r.rem += denom; |
| } |
| return (r); |
| } |