ldiv.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/*
 * ldiv.c
 * Original Author:	G. Haley
 *
 * Computes the quotient and remainder of the division of the numerator n by
 * the denominator d. If the division is inexact, the sign of the quotient is
 * that of the mathematical quotient, and the magnitude of the quotient is the
 * largest integer less than the magnitude of the mathematical quotient. If the
 * result cannot be represented, the behaviour is undefined. Returns the
 * results in a structure of type ldiv_t, comprising the following members:
 *
 *	long quot;
 *	long rem;
 */

/*
FUNCTION
<<ldiv>>---divide two long integers

INDEX
	ldiv

ANSI_SYNOPSIS
	#include <stdlib.h>
	ldiv_t ldiv(long <[n]>, long <[d]>);

TRAD_SYNOPSIS
	#include <stdlib.h>
	ldiv_t ldiv(<[n]>, <[d]>)
	long <[n]>, <[d]>;

DESCRIPTION
Divide
@tex
$n/d$,
@end tex
@ifinfo
<[n]>/<[d]>,
@end ifinfo
returning quotient and remainder as two integers in a structure <<ldiv_t>>.

RETURNS
The result is represented with the structure

. typedef struct
. {
.  long quot;
.  long rem;
. } ldiv_t;

where the <<quot>> field represents the quotient, and <<rem>> the
remainder.  For nonzero <[d]>, if `<<<[r]> = ldiv(<[n]>,<[d]>);>>' then
<[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'.

When <[d]> is zero, the <<quot>> member of the result has the same
sign as <[n]> and the largest representable magnitude.

To divide <<int>> rather than <<long>> values, use the similar
function <<div>>.

PORTABILITY
<<ldiv>> is ANSI, but the behavior for zero <[d]> is not specified by
the standard.

No supporting OS subroutines are required.
*/

#include <limits.h>
#include <stdlib.h>

ldiv_t 
ldiv (n, d)
     long n, d;
{
  ldiv_t res;

  if (d)
    {
      res.quot = labs (n) / labs (d);
      res.rem = labs (n) % labs (d);

      if ((n < 0 && d > 0) || (n >= 0 && d < 0))
	res.quot = -res.quot;
      if (n < 0)
	res.rem = -res.rem;
    }
  else
    {
      if (n < 0)
	res.quot = LONG_MIN;
      else
	res.quot = LONG_MAX;

      res.rem = 0;
    }

  return res;
}