modf(), modff(), modfl()

Break a number into integral and fractional parts

Synopsis:

#include <math.h>

double modf( double value,
             double* iptr );

float modff( float value,
             float* iptr );

long double modfl( long double value,
                   long double* iptr );

Arguments:

value: The value that you want to break into parts.
iptr: A pointer to a location where the function can store the integral part of the number.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

The modf(), modff(), and modfl() functions break the given value into integral and fractional parts, each of which has the same sign as the argument. They store the integral part in the object pointed to by iptr.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

Call feclearexcept(FE_ALL_EXCEPT) before calling modf(), modff(), or modfl().
On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

Returns:

The signed fractional part of value.

If `value` is:	These functions return:	And set *`iptr` to:	Errors:
±Inf	0.0, with the same sign as `value`	Inf, with the same sign as `value`	—
NaN	NaN	NaN	—

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

Examples:

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

int main( void )
{
    double integral_value, fractional_part;

    fractional_part = modf( 4.5, &integral_value );
    printf( "%f %f\n", fractional_part, integral_value );
    
    fractional_part = modf( -4.5, &integral_value );
    printf( "%f %f\n", fractional_part, integral_value );
    
    return EXIT_SUCCESS;
}

produces the output:

0.500000 4.000000
-0.500000 -4.000000

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	Yes