Compute the positive different between two floatingpoint 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 );
Arguments:
 x, y
 The numbers that you want to compute the difference between.
Library:
libm
Use the l m option to
qcc
to link against this library.
Description:
The fdim(), fdimf(), and fdiml() functions
compute the positive different between two floatingpoint numbers.
If x is greater than y, then these function return
x  y.
If x is less than or equal to y, these functions return +0.
To check for error situations, use
feclearexcept()
and
fetestexcept():
 Call feclearexcept(FE_ALL_EXCEPT) before calling
fdim(), fdimf(), or fdiml().
 On return, if fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVERFLOW  FE_UNDERFLOW)
is nonzero, then an error has occurred.
Returns:
The positive difference.
 If x  y is positive and overflows, a range error occurs,
and these functions return HUGE_VAL, HUGE_VALF, and HUGE_VALL,
respectively.
 If the correct value would cause an underflow, a range error may occur, and these functions return
the correct value, or (if the IEC 60559 FloatingPoint option isn't supported) a value no greater
in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
 If x or y is NaN, NaN is returned.
Errors:
 FE_OVERFLOW
 The result overflows.
 FE_UNDERFLOW
 The result underflows.
Classification:
ANSI,
POSIX 1003.1
Safety: 

Cancellation point 
No 
Interrupt handler 
No 
Signal handler 
No 
Thread 
Yes 