fmod.c

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/* fmod.c - fmod math routine */

/* Copyright 1992-1993 Wind River Systems, Inc. */

/*
modification history
--------------------
01g,05feb99,dgp  document errno values
01f,05feb93,jdi  doc changes based on kdl review.
01e,02dec92,jdi  doc tweaks.
01d,28oct92,jdi  documentation cleanup.
01c,20sep92,smb  documentation additions
01b,30jul92,kdl  changed _d_type() calls to fpTypeGet().
01a,08jul92,smb  documentation.
*/

/*
DESCRIPTION
SEE ALSO: American National Standard X3.159-1989
NOMANUAL
*/

#include "vxWorks.h"
#include "math.h"
#include "stddef.h"
#include "errno.h"
#include "private/mathP.h"


/*******************************************************************************
*
* fmod - compute the remainder of x/y (ANSI)
*
* This routine returns the remainder of <x>/<y> with the sign of <x>,
* in double precision.
* 
* INCLUDE FILES: math.h
*
* RETURNS: The value <x> - <i> * <y>, for some integer <i>.  If <y> is
* non-zero, the result has the same sign as <x> and magnitude less than the
* magnitude of <y>.  If <y> is zero, fmod() returns zero.
*
* ERRNO: EDOM
*
* SEE ALSO: mathALib
*/

double fmod
    (
    double x,	/* numerator   */
    double y	/* denominator */
    )

    {
    double	t;
    short	negative = 0;
    int		errx = fpTypeGet (x, NULL);	/* determine number type */
    int		erry = fpTypeGet (y, NULL);	/* determine number type */

    if (errx == NAN || erry == NAN || errx == INF || erry == ZERO)
        {
        errno = EDOM;				/* Domain error */
        return ((errx == NAN) ? (x) : ((erry == NAN) ? (y) : (0)));
        }
    
    if (errx == ZERO || erry == INF)
	return (x);		

    /* make x and y absolute */

    if (y < 0.0)
	y = -y;

    if (x < 0.0)
	{
	x = -x;
	negative = 1;
	}

    /* loop substracting y from x until a value less than y remains */

    for (t = x; t > y; t -= y)
        ;

    return ((t == y) ? (0.0) : ((negative) ? (-t) : (t)));
    }