1EXP2(3P) POSIX Programmer's Manual EXP2(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 exp2, exp2f, exp2l — exponential base 2 functions
13
15 #include <math.h>
16 double exp2(double x);
18 float exp2f(float x);
19 long double exp2l(long double x);
20
22 The functionality described on this reference page is aligned with the
23 ISO C standard. Any conflict between the requirements described here
24 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
25 defers to the ISO C standard.
26 These functions shall compute the base-2 exponential of x.
28 An application wishing to check for error situations should set errno
30 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
31 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
32 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
33 occurred.
34
36 Upon successful completion, these functions shall return 2x.
37 If the correct value would cause overflow, a range error shall occur
39 and exp2(), exp2f(), and exp2l() shall return the value of the macro
40 HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
41 If the correct value would cause underflow, and is not representable, a
43 range error may occur, and exp2(), exp2f(), and exp2l() shall return
44 0.0, or (if the IEC 60559 Floating-Point option is not supported) an
45 implementation-defined value no greater in magnitude than DBL_MIN,
46 FLT_MIN, and LDBL_MIN, respectively.
47 If x is NaN, a NaN shall be returned.
49 If x is ±0, 1 shall be returned.
51 If x is -Inf, +0 shall be returned.
53 If x is +Inf, x shall be returned.
55 If the correct value would cause underflow, and is representable, a
57 range error may occur and the correct value shall be returned.
58
60 These functions shall fail if:
61 Range Error The result overflows.
63 If the integer expression (math_errhandling & MATH_ERRNO)
65 is non-zero, then errno shall be set to [ERANGE]. If the
66 integer expression (math_errhandling & MATH_ERREXCEPT) is
67 non-zero, then the overflow floating-point exception shall
68 be raised.
69 These functions may fail if:
71 Range Error The result underflows.
73 If the integer expression (math_errhandling & MATH_ERRNO)
75 is non-zero, then errno shall be set to [ERANGE]. If the
76 integer expression (math_errhandling & MATH_ERREXCEPT) is
77 non-zero, then the underflow floating-point exception shall
78 be raised.
79 The following sections are informative.
81
83 None.
84
86 On error, the expressions (math_errhandling & MATH_ERRNO) and
87 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
88 at least one of them must be non-zero.
89
91 None.
92
94 None.
95
97 exp(), feclearexcept(), fetestexcept(), isnan(), log()
98 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
100 Error Conditions for Mathematical Functions, <math.h>
101
103 Portions of this text are reprinted and reproduced in electronic form
104 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
105 table Operating System Interface (POSIX), The Open Group Base Specifi‐
106 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
107 Electrical and Electronics Engineers, Inc and The Open Group. In the
108 event of any discrepancy between this version and the original IEEE and
109 The Open Group Standard, the original IEEE and The Open Group Standard
110 is the referee document. The original Standard can be obtained online
111 at http://www.opengroup.org/unix/online.html .
112 Any typographical or formatting errors that appear in this page are
114 most likely to have been introduced during the conversion of the source
115 files to man page format. To report such errors, see https://www.ker‐
116 nel.org/doc/man-pages/reporting_bugs.html .
117IEEE/The Open Group 2017 EXP2(3P)