Other Alias
modf, modflSYNOPSIS
#include <math.h>
double modf(double x, double *iptr);
float modff(float value, float *iptr);
long double modfl(long double value, long double *iptr);
DESCRIPTION
These functions shall break the argument x into integral and fractional parts, each of which has the same sign as the argument. It stores the integral part as a double (for the modf() function), a float (for the modff() function), or a long double (for the modfl() function), in the object pointed to by iptr.
RETURN VALUE
Upon successful completion, these functions shall return the signed fractional part of x.
If x is NaN, a NaN shall be returned, and *iptr shall be set to a NaN.
If x is ±Inf, ±0 shall be returned, and *iptr shall be set to ±Inf.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The modf() function computes the function result and *iptr such that:

a = modf(x, iptr) ; x == a+*iptr ;
allowing for the usual floatingpoint inaccuracies.
RATIONALE
None.
FUTURE DIRECTIONS
None.
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology  Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 20012003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .