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modf, modff

Splits a floating-point value into fractional and integer parts.

double modf(
   double x,
   double *intptr 
float modf(
   float x,
   float *intptr
);  // C++ only
long double modf(
   long double x,
   long double * intptr
);  // C++ only
float modff(
   float x,
   float *intptr 


Floating-point value.
Pointer to stored integer portion.

Return Value

This function returns the signed fractional portion of x. There is no error return.


The modf function breaks down the floating-point value x into fractional and integer parts, each of which has the same sign as x. The signed fractional portion of x is returned. The integer portion is stored as a floating-point value at intptr.

modf has an implementation that uses Streaming SIMD Extensions 2 (SSE2). See _set_SSE2_enable for information and restrictions on using the SSE2 implementation.

C++ allows overloading, so you can call overloads of modf. In a C program, modf always takes two double values and returns a double value.


Routine Required header Compatibility
modf, modff <math.h> ANSI, Win 98, Win Me, Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.


All versions of the C run-time libraries.


// crt_modf.c

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

int main( void )
   double x, y, n;

   x = -14.87654321;      /* Divide x into its fractional */
   y = modf( x, &n );     /* and integer parts            */

   printf( "For %f, the fraction is %f and the integer is %.f\n", 
           x, y, n );


For -14.876543, the fraction is -0.876543 and the integer is -14

See Also

Floating-Point Support Routines | Long Double | frexp | ldexp | Run-Time Routines and .NET Framework Equivalents