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Linux 2.6 - man page for fdim (linux section 3posix)

FDIM(P) 			    POSIX Programmer's Manual				  FDIM(P)

NAME
       fdim, fdimf, fdiml - compute positive difference between two floating-point numbers

SYNOPSIS
       #include <math.h>

       double fdim(double x, double y);
       float fdimf(float x, float y);
       long double fdiml(long double x, long double y);

DESCRIPTION
       These  functions  shall determine the positive difference between their arguments. If x is
       greater than y, x- y is returned. If x is less than or equal to y, +0 is returned.

       An application wishing to check for error situations should set errno  to  zero	and  call
       feclearexcept(FE_ALL_EXCEPT)  before calling these functions.  On return, if errno is non-
       zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is	non-zero,
       an error has occurred.

RETURN VALUE
       Upon successful completion, these functions shall return the positive difference value.

       If  x-  y  is  positive	and overflows, a range error shall occur and fdim(), fdimf(), and
       fdiml() shall return the value of the macro HUGE_VAL, HUGE_VALF,  and  HUGE_VALL,  respec-
       tively.

       If x- y is positive and underflows, a range error may occur, and either ( x- y) (if repre-
       sentable),  or 0.0 (if supported),  or an implementation-defined value shall be returned.

       If x or y is NaN, a NaN shall be returned.

ERRORS
       The fdim() function shall fail if:

       Range Error
	      The result overflows.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
       set  to	[ERANGE].  If  the integer expression (math_errhandling & MATH_ERREXCEPT) is non-
       zero, then the overflow floating-point exception shall be raised.

       The fdim() function may fail if:

       Range Error
	      The result underflows.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
       set  to	[ERANGE].  If  the integer expression (math_errhandling & MATH_ERREXCEPT) is non-
       zero, then the underflow floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       On implementations supporting IEEE Std 754-1985, x- y cannot underflow, and hence the  0.0
       return  value  is  shaded as an extension for implementations supporting the XSI extension
       rather than an MX extension.

       On  error,  the	expressions  (math_errhandling	&  MATH_ERRNO)	and  (math_errhandling	&
       MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feclearexcept()	,  fetestexcept()  ,  fmax()  ,  fmin()  , the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for  Mathematical  Func-
       tions, <math.h>

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) 2001-2003 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  FDIM(P)


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