1LDEXP(3P) POSIX Programmer's Manual LDEXP(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 ldexp, ldexpf, ldexpl — load exponent of a floating-point number
13
15 #include <math.h>
16 double ldexp(double x, int exp);
18 float ldexpf(float x, int exp);
19 long double ldexpl(long double x, int exp);
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 quantity x * 2exp.
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 x multiplied
37 by 2, raised to the power exp.
38 If these functions would cause overflow, a range error shall occur and
40 ldexp(), ldexpf(), and ldexpl() shall return ±HUGE_VAL, ±HUGE_VALF, and
41 ±HUGE_VALL (according to the sign of x), respectively.
42 If the correct value would cause underflow, and is not representable, a
44 range error may occur, and ldexp(), ldexpf(), and ldexpl() shall return
45 0.0, or (if IEC 60559 Floating-Point is not supported) an implementa‐
46 tion-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and
47 LDBL_MIN, respectively.
48 If x is NaN, a NaN shall be returned.
50 If x is ±0 or ±Inf, x shall be returned.
52 If exp is 0, x shall be returned.
54 If the correct value would cause underflow, and is representable, a
56 range error may occur and the correct value shall be returned.
57
59 These functions shall fail if:
60 Range Error The result overflows.
62 If the integer expression (math_errhandling & MATH_ERRNO)
64 is non-zero, then errno shall be set to [ERANGE]. If the
65 integer expression (math_errhandling & MATH_ERREXCEPT) is
66 non-zero, then the overflow floating-point exception shall
67 be raised.
68 These functions may fail if:
70 Range Error The result underflows.
72 If the integer expression (math_errhandling & MATH_ERRNO)
74 is non-zero, then errno shall be set to [ERANGE]. If the
75 integer expression (math_errhandling & MATH_ERREXCEPT) is
76 non-zero, then the underflow floating-point exception shall
77 be raised.
78 The following sections are informative.
80
82 None.
83
85 On error, the expressions (math_errhandling & MATH_ERRNO) and
86 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
87 at least one of them must be non-zero.
88
90 None.
91
93 None.
94
96 feclearexcept(), fetestexcept(), frexp(), isnan()
97 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
99 Error Conditions for Mathematical Functions, <math.h>
100
102 Portions of this text are reprinted and reproduced in electronic form
103 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
104 table Operating System Interface (POSIX), The Open Group Base Specifi‐
105 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
106 Electrical and Electronics Engineers, Inc and The Open Group. In the
107 event of any discrepancy between this version and the original IEEE and
108 The Open Group Standard, the original IEEE and The Open Group Standard
109 is the referee document. The original Standard can be obtained online
110 at http://www.opengroup.org/unix/online.html .
111 Any typographical or formatting errors that appear in this page are
113 most likely to have been introduced during the conversion of the source
114 files to man page format. To report such errors, see https://www.ker‐
115 nel.org/doc/man-pages/reporting_bugs.html .
116IEEE/The Open Group 2017 LDEXP(3P)