1FDIM(3P) POSIX Programmer's Manual FDIM(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 fdim, fdimf, fdiml — compute positive difference between two floating-
14 point numbers
15
17 #include <math.h>
18 double fdim(double x, double y);
20 float fdimf(float x, float y);
21 long double fdiml(long double x, long double y);
22
24 The functionality described on this reference page is aligned with the
25 ISO C standard. Any conflict between the requirements described here
26 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
27 defers to the ISO C standard.
28 These functions shall determine the positive difference between their
30 arguments. If x is greater than y, x−y is returned. If x is less than
31 or equal to y, +0 is returned.
32 An application wishing to check for error situations should set errno
34 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
35 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
36 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
37 occurred.
38
40 Upon successful completion, these functions shall return the positive
41 difference value.
42 If x−y is positive and overflows, a range error shall occur and fdim(),
44 fdimf(), and fdiml() shall return the value of the macro HUGE_VAL,
45 HUGE_VALF, and HUGE_VALL, respectively.
46 If the correct value would cause underflow, a range error may occur,
48 and fdim(), fdimf(), and fdiml() shall return the correct value, or (if
49 the IEC 60559 Floating-Point option is not supported) an implementa‐
50 tion-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and
51 LDBL_MIN, respectively.
52 If x or y is NaN, a NaN shall be returned.
54
56 The fdim() function shall fail if:
57 Range Error The result overflows.
59 If the integer expression (math_errhandling & MATH_ERRNO)
61 is non-zero, then errno shall be set to [ERANGE]. If the
62 integer expression (math_errhandling & MATH_ERREXCEPT) is
63 non-zero, then the overflow floating-point exception shall
64 be raised.
65 The fdim() function may fail if:
67 Range Error The result underflows.
69 If the integer expression (math_errhandling & MATH_ERRNO)
71 is non-zero, then errno shall be set to [ERANGE]. If the
72 integer expression (math_errhandling & MATH_ERREXCEPT) is
73 non-zero, then the underflow floating-point exception shall
74 be raised.
75 The following sections are informative.
77
79 None.
80
82 On error, the expressions (math_errhandling & MATH_ERRNO) and
83 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
84 at least one of them must be non-zero.
85
87 None.
88
90 None.
91
93 feclearexcept(), fetestexcept(), fmax(), fmin()
94 Section 4.19, Treatment of Error Conditions for Mathematical Functions,
96 <math.h>
97
99 Portions of this text are reprinted and reproduced in electronic form
100 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
101 -- Portable Operating System Interface (POSIX), The Open Group Base
102 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
103 cal and Electronics Engineers, Inc and The Open Group. (This is
104 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
105 event of any discrepancy between this version and the original IEEE and
106 The Open Group Standard, the original IEEE and The Open Group Standard
107 is the referee document. The original Standard can be obtained online
108 at http://www.unix.org/online.html .
109 Any typographical or formatting errors that appear in this page are
111 most likely to have been introduced during the conversion of the source
112 files to man page format. To report such errors, see https://www.ker‐
113 nel.org/doc/man-pages/reporting_bugs.html .
114IEEE/The Open Group 2013 FDIM(3P)