C in a Nutshell

Name

modf

Synopsis

Separates a floating-point number into integer and fraction parts

#include <math.h>
doublemodf( double x, double *intpart );
float modff( float x, float *intpart );        (C99)
long double modfl( long double x, long double *intpart );        (C99)

The modf() functions analyze a floating-point number into an integer and a fraction whose magnitude is less than one. The integer part is stored in the location addressed by the second argument, and fractional part is the return value.

Tip

There is no type-generic macro for the modf() functions.

Example

double x, integer = 0.0, fraction = 0.0;
x = 1.23;
fraction = modf( x, &integer );
printf("%10f = %f + %f\n", x , integer, fraction );

x = -1.23;
fraction = modf( x, &integer );
printf("%10f = %f + %f\n", x , integer, fraction );

The example produces the following output:

  1.230000 = 1.000000 + 0.230000
 -1.230000 = -1.000000 + -0.230000

See Also

frexp()