modf, modff, modfl

Article
06/05/2017

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

Syntax

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   
);  
long double modfl(  
   long double x,  
   long double * intptr  
);

Parameters

x
Floating-point value.

intptr
Pointer to stored integer portion.

Return Value

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

Remarks

The modf functions break 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 that take and return float or long double parameters. In a C program, modf always takes two double values and returns a double value.

Requirements

Routine	Required header
`modf`, `modff`, `modfl`	C: <math.h> C++: , <cmath> or <math.h>

For additional compatibility information, see Compatibility in the Introduction.

Libraries

All versions of the C run-time libraries.

Example

// 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 );  
}

Output

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

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