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FDIM(3P)                   POSIX Programmer's Manual                  FDIM(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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
       The  functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the  requirements  described  here
       and  the  ISO C  standard is unintentional. This volume of POSIX.1-2008
       defers to the ISO C standard.
       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, respectively.
       If  the  correct  value would cause underflow, a range error may occur,
       and fdim(), fdimf(), and fdiml() shall return the correct value, or (if
       the  IEC  60559  Floating-Point option is not supported) an implementa-
       tion-defined value no greater in magnitude than DBL_MIN,  FLT_MIN,  and
       LDBL_MIN, respectively.
       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   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()
       Section 4.19, Treatment of Error Conditions for Mathematical Functions,
       <math.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                             FDIM(3P)