Legacy Document

modf

You can use the modf function to split a real number into a fractional part and an integer part.

float modff (float x, float *iptrf);
double modf (double x, double *iptr);

x

Any floating-point number.

iptr

A pointer to a floating-point variable in which the integer part can be stored upon return.

DESCRIPTION

The modf function splits its first argument into a fractional part and an integer part. This is an ANSI standard C function.

 such that |f| < 1.0 and 

The fractional part is returned as the value of the function, and the integer part is stored as a floating-point number in the area pointed to by iptr. The fractional part and the integer part both have the same sign as the argument x.

EXCEPTIONS

If x is finite and nonzero, the result of $modf(x,n)$ is exact.

SPECIAL CASES

Table 10-19 shows the results when the floating-point argument to the modf function is a zero, a NaN, or an Infinity.

Special cases for the modf function

Operation	Result	Exceptions raised
$modf(+0,n)$	+0 (n = 0)	None
$modf(-0,n)$	$-0$ (n = 0)	None
$modf(NaN,n)$	NaN (n = NaN)	None[40]
$modf(+$ ,n)	+0 (n = + )	None
$modf(-$ ,n)	$-0$ (n = $-$ )	None

EXAMPLES

z = modf(1.0, n); /* z = 0.0 and n = 1.0 */
z = modf(+INFINITY, n); /* z = 0.0 and n = +INFINITY because the 
                           value +   is an integer. */

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[40] If the NaN is a signaling NaN, the invalid exception is raised.