fmod(3) Library Functions Manual fmod(3)
NAME
fmod, drem, remainder - Compute the floating-point remainder
LIBRARY
Math Library (libm.a)
SYNOPSIS
#include <math.h>
double fmod (double x, double y); float fmodf (float x, float y); long double fmodl (long double x,
long double y); double drem (double x, double y); float dremf (float x, float y); long double dreml
(long double x, long double y); double remainder (double x, double y); float remainderf (float x, float y); long double
remainderl (long double x, long double y);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
fmod(): XPG4
remainder(): XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
DESCRIPTION
The fmod(), fmodf(), and fmodl() functions return the remainder r = x - n*y, where n = trunc(x/y). The result has the same sign as x and
magnitude less than the magnitude of y. The remainder is computed exactly and |r| is less than |y|.
The drem(), dremf(), dreml(), remainder(), remainderf(), and remainderl() functions return the remainder r = x - n*y, where n = rint(x/y).
Additionally, if |n - x/y|=1/2, then n is even. The remainder is computed exactly and |r| is less than or equal to |y|/2.
The drem() and remainder() functions are aliases of each other. The dremf(), and remainderf() functions are aliases of each other. The
dreml() and remainderl() functions are aliases of each other.
The following table describes function behavior in response to exceptional arguments:
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Function Exceptional Argument Routine Behavior
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fmod(), fmodf(), fmodl() x = infinity Invalid argument
fmod(), fmodf(), fmodl() y = 0 Invalid argument
drem(), dremf(), dreml() x = infinity Invalid argument
drem(), dremf(), dreml() y = 0 Invalid argument
remainder() x = infinity Invalid argument
remainderf() x = infinity Invalid argument
remainderl() x = infinity Invalid argument
remainder() y = 0 Invalid argument
remainderf() y = 0 Invalid argument
remainderl() y = 0 Invalid argument
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fmod(3)
