ldexpf(3p)

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

PROLOG

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

NAME

12       ldexp, ldexpf, ldexpl - load exponent of a floating-point number
13

SYNOPSIS

15       #include <math.h>
16
17       double ldexp(double x, int exp);
18       float ldexpf(float x, int exp);
19       long double ldexpl(long double x, int exp);
20
21

DESCRIPTION

23       These functions shall compute the quantity x * 2**exp.
24
25       An application wishing to check for error situations should  set  errno
26       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
27       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
28       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
29       occurred.
30

RETURN VALUE

32       Upon successful completion, these functions shall return  x  multiplied
33       by 2, raised to the power exp.
34
35       If  these functions would cause overflow, a range error shall occur and
36       ldexp(), ldexpf(), and ldexpl() shall return ±HUGE_VAL, ±HUGE_VALF, and
37       ±HUGE_VALL (according to the sign of x), respectively.
38
39       If the correct value would cause underflow, and is not representable, a
40       range error may occur, and  either 0.0 (if supported), or an  implemen‐
41       tation-defined value shall be returned.
42
43       If x is NaN, a NaN shall be returned.
44
45       If x is ±0 or ±Inf, x shall be returned.
46
47       If exp is 0, x shall be returned.
48
49       If  the  correct  value  would cause underflow, and is representable, a
50       range error may occur and the correct value shall be returned.
51

ERRORS

53       These functions shall fail if:
54
55       Range Error
56              The result overflows.
57
58       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
59       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
60       (math_errhandling & MATH_ERREXCEPT)  is  non-zero,  then  the  overflow
61       floating-point exception shall be raised.
62
63
64       These functions may fail if:
65
66       Range Error
67              The result underflows.
68
69       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
70       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
71       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow
72       floating-point exception shall be raised.
73
74
75       The following sections are informative.
76

EXAMPLES

78       None.
79

APPLICATION USAGE

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

RATIONALE

86       None.
87

FUTURE DIRECTIONS

89       None.
90

COPYRIGHT

97       Portions of this text are reprinted and reproduced in  electronic  form
98       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
99       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
100       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
101       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
102       event of any discrepancy between this version and the original IEEE and
103       The Open Group Standard, the original IEEE and The Open Group  Standard
104       is  the  referee document. The original Standard can be obtained online
105       at http://www.opengroup.org/unix/online.html .
106
107
108
109IEEE/The Open Group                  2003                            LDEXP(3P)