1FDIM(P)                    POSIX Programmer's Manual                   FDIM(P)
2
3
4

NAME

6       fdim,  fdimf, fdiml - compute positive difference between two floating-
7       point numbers
8

SYNOPSIS

10       #include <math.h>
11
12       double fdim(double x, double y);
13       float fdimf(float x, float y);
14       long double fdiml(long double x, long double y);
15
16

DESCRIPTION

18       These functions shall determine the positive difference  between  their
19       arguments.  If x is greater than y, x- y is returned. If x is less than
20       or equal to y, +0 is returned.
21
22       An application wishing to check for error situations should  set  errno
23       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
24       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
25       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
26       occurred.
27

RETURN VALUE

29       Upon successful completion, these functions shall return  the  positive
30       difference value.
31
32       If  x-  y  is  positive  and  overflows,  a range error shall occur and
33       fdim(), fdimf(), and fdiml()  shall  return  the  value  of  the  macro
34       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
35
36       If x- y is positive and underflows, a range error may occur, and either
37       ( x- y) (if representable),  or 0.0 (if supported),  or an  implementa‐
38       tion-defined value shall be returned.
39
40       If x or y is NaN, a NaN shall be returned.
41

ERRORS

43       The fdim() function shall fail if:
44
45       Range Error
46              The result overflows.
47
48       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
49       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
50       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow
51       floating-point exception shall be raised.
52
53
54       The fdim() function may fail if:
55
56       Range Error
57              The result underflows.
58
59       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
60       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
61       (math_errhandling & MATH_ERREXCEPT) is  non-zero,  then  the  underflow
62       floating-point exception shall be raised.
63
64
65       The following sections are informative.
66

EXAMPLES

68       None.
69

APPLICATION USAGE

71       On implementations supporting IEEE Std 754-1985, x- y cannot underflow,
72       and hence the 0.0 return value is shaded as an extension for  implemen‐
73       tations supporting the XSI extension rather than an MX extension.
74
75       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
76       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
77       at least one of them must be non-zero.
78

RATIONALE

80       None.
81

FUTURE DIRECTIONS

83       None.
84

SEE ALSO

86       feclearexcept()  ,  fetestexcept() , fmax() , fmin() , the Base Defini‐
87       tions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of  Error
88       Conditions for Mathematical Functions, <math.h>
89

91       Portions  of  this text are reprinted and reproduced in electronic form
92       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
93       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
94       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
95       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
96       event of any discrepancy between this version and the original IEEE and
97       The  Open Group Standard, the original IEEE and The Open Group Standard
98       is the referee document. The original Standard can be  obtained  online
99       at http://www.opengroup.org/unix/online.html .
100
101
102
103IEEE/The Open Group                  2003                              FDIM(P)
Impressum