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
12 fdim, fdimf, fdiml — compute positive difference between two floating-
13 point numbers
14
16 #include <math.h>
17 double fdim(double x, double y);
19 float fdimf(float x, float y);
20 long double fdiml(long double x, long double y);
21
23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
26 defers to the ISO C standard.
27 These functions shall determine the positive difference between their
29 arguments. If x is greater than y, x-y is returned. If x is less than
30 or equal to y, +0 is returned.
31 An application wishing to check for error situations should set errno
33 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
34 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
35 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
36 occurred.
37
39 Upon successful completion, these functions shall return the positive
40 difference value.
41 If x-y is positive and overflows, a range error shall occur and fdim(),
43 fdimf(), and fdiml() shall return the value of the macro HUGE_VAL,
44 HUGE_VALF, and HUGE_VALL, respectively.
45 If the correct value would cause underflow, a range error may occur,
47 and fdim(), fdimf(), and fdiml() shall return the correct value, or (if
48 the IEC 60559 Floating-Point option is not supported) an implementa‐
49 tion-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and
50 LDBL_MIN, respectively.
51 If x or y is NaN, a NaN shall be returned.
53
55 The fdim() function shall fail if:
56 Range Error The result overflows.
58 If the integer expression (math_errhandling & MATH_ERRNO)
60 is non-zero, then errno shall be set to [ERANGE]. If the
61 integer expression (math_errhandling & MATH_ERREXCEPT) is
62 non-zero, then the overflow floating-point exception shall
63 be raised.
64 The fdim() function may fail if:
66 Range Error The result underflows.
68 If the integer expression (math_errhandling & MATH_ERRNO)
70 is non-zero, then errno shall be set to [ERANGE]. If the
71 integer expression (math_errhandling & MATH_ERREXCEPT) is
72 non-zero, then the underflow floating-point exception shall
73 be raised.
74 The following sections are informative.
76
78 None.
79
81 On error, the expressions (math_errhandling & MATH_ERRNO) and
82 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
83 at least one of them must be non-zero.
84
86 None.
87
89 None.
90
92 feclearexcept(), fetestexcept(), fmax(), fmin()
93 Section 4.20, Treatment of Error Conditions for Mathematical Functions,
95 <math.h>
96
98 Portions of this text are reprinted and reproduced in electronic form
99 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
100 table Operating System Interface (POSIX), The Open Group Base Specifi‐
101 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
102 Electrical and Electronics Engineers, Inc and The Open Group. In the
103 event of any discrepancy between this version and the original IEEE and
104 The Open Group Standard, the original IEEE and The Open Group Standard
105 is the referee document. The original Standard can be obtained online
106 at http://www.opengroup.org/unix/online.html .
107 Any typographical or formatting errors that appear in this page are
109 most likely to have been introduced during the conversion of the source
110 files to man page format. To report such errors, see https://www.ker‐
111 nel.org/doc/man-pages/reporting_bugs.html .
112IEEE/The Open Group 2017 FDIM(3P)