/*      $NetBSD: n_fmod.c,v 1.11 2018/11/09 10:19:47 martin Exp $       */
/*
* Copyright (c) 1989, 1993
*      The Regents of the University of California.  All rights reserved.
*
* 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. 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.
*/

#ifndef lint
#if 0
static char sccsid[] = "@(#)fmod.c      8.1 (Berkeley) 6/4/93";
#endif
#endif /* not lint */

#include "mathimpl.h"

/* fmod.c
*
* SYNOPSIS
*
*    #include <math.h>
*    double fmod(double x, double y)
*
* DESCRIPTION
*
*    The fmod function computes the floating-point remainder of x/y.
*
* RETURNS
*
*    The fmod function returns the value x-i*y, for some integer i
* such that, if y is nonzero, the result has the same sign as x and
* magnitude less than the magnitude of y.
*
* On a VAX or CCI,
*
*    fmod(x,0) traps/faults on floating-point divided-by-zero.
*
* On IEEE-754 conforming machines with "isnan()" primitive,
*
*    fmod(x,0), fmod(INF,y) are invalid operations and NaN is returned.
*
*/
#if !defined(__vax__) && !defined(tahoe)
extern int isnan(),finite();
#endif  /* !defined(__vax__) && !defined(tahoe) */

#if DBL_MANT_DIG == LDBL_MANT_DIG && DBL_MIN_EXP == LDBL_MIN_EXP \
        && DBL_MIN_EXP == LDBL_MIN_EXP
#ifdef __weak_alias
__weak_alias(fmodl, fmod);
__weak_alias(modfl, fmod);
#endif
#endif

#ifdef TEST_FMOD
static double
_fmod(double x, double y)
#else   /* TEST_FMOD */
double
fmod(double x, double y)
#endif  /* TEST_FMOD */
{
       int ir,iy;
       double r,w;

       if (y == (double)0
#if !defined(__vax__) && !defined(tahoe)        /* per "fmod" manual entry, SunOS 4.0 */
               || isnan(y) || !finite(x)
#endif  /* !defined(__vax__) && !defined(tahoe) */
           )
           return (x*y)/(x*y);

       r = fabs(x);
       y = fabs(y);
       (void)frexp(y,&iy);
       while (r >= y) {
               (void)frexp(r,&ir);
               w = ldexp(y,ir-iy);
               r -= w <= r ? w : w*(double)0.5;
       }
       return x >= (double)0 ? r : -r;
}

float
fmodf(float x, float y)
{
       return fmod(x, y);
}

#ifdef TEST_FMOD
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#define NTEST   10000
#define NCASES  3

static int nfail = 0;
static void
prf(const char *s, double d)
{
       union {
               double d;
               unsigned long long u;
       } x;
       x.d = d;
       printf("%s = %#016.16llx (%24.16e)\n", s, x.u, x.d);
}

static void
doit(double x, double y)
{
       double ro = fmod(x,y),rn = _fmod(x,y);
       if (ro != rn) {
               prf(" x   ", x);
               prf(" y   ", y);
               prf(" fmod", ro);
               prf("_fmod", rn);
               (void)printf("\n");
       }
}

int
main(int argc, char **argv)
{
       int i,cases;
       double x,y;

       srandom(12345);
       for (i = 0; i < NTEST; i++) {
               x = (double)random();
               y = (double)random();
               for (cases = 0; cases < NCASES; cases++) {
                       switch (cases) {
                       case 0:
                               break;
                       case 1:
                               y = (double)1/y; break;
                       case 2:
                               x = (double)1/x; break;
                       default:
                               abort(); break;
                       }
                       doit(x,y);
                       doit(x,-y);
                       doit(-x,y);
                       doit(-x,-y);
               }
       }
       if (nfail)
               (void)printf("Number of failures: %d (out of a total of %d)\n",
                       nfail,NTEST*NCASES*4);
       else
               (void)printf("No discrepancies were found\n");
       exit(0);
}
#endif  /* TEST_FMOD */