1LDEXP(3P)                  POSIX Programmer's Manual                 LDEXP(3P)
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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.
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11

NAME

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

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

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.1‐2008
26       defers to the ISO C standard.
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28       These functions shall compute the quantity x * 2exp.
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30       An  application  wishing to check for error situations should set errno
31       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these
32       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33       FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero,  an  error  has
34       occurred.
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RETURN VALUE

37       Upon  successful  completion, these functions shall return x multiplied
38       by 2, raised to the power exp.
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40       If these functions would cause overflow, a range error shall occur  and
41       ldexp(), ldexpf(), and ldexpl() shall return ±HUGE_VAL, ±HUGE_VALF, and
42       ±HUGE_VALL (according to the sign of x), respectively.
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44       If the correct value would cause underflow, and is not representable, a
45       range error may occur, and ldexp(), ldexpf(), and ldexpl() shall return
46       0.0, or (if IEC 60559 Floating-Point is not supported)  an  implementa‐
47       tion-defined  value  no greater in magnitude than DBL_MIN, FLT_MIN, and
48       LDBL_MIN, respectively.
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50       If x is NaN, a NaN shall be returned.
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52       If x is ±0 or ±Inf, x shall be returned.
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54       If exp is 0, x shall be returned.
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56       If the correct value would cause underflow,  and  is  representable,  a
57       range error may occur and the correct value shall be returned.
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ERRORS

60       These functions shall fail if:
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62       Range Error The result overflows.
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64                   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.
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70       These functions may fail if:
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72       Range Error The result underflows.
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74                   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.
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80       The following sections are informative.
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EXAMPLES

83       None.
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APPLICATION USAGE

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.
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RATIONALE

91       None.
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FUTURE DIRECTIONS

94       None.
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SEE ALSO

97       feclearexcept(), fetestexcept(), frexp(), isnan()
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99       The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
100       Error Conditions for Mathematical Functions, <math.h>
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103       Portions of this text are reprinted and reproduced in  electronic  form
104       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
105       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
106       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
107       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
108       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
109       event of any discrepancy between this version and the original IEEE and
110       The  Open Group Standard, the original IEEE and The Open Group Standard
111       is the referee document. The original Standard can be  obtained  online
112       at http://www.unix.org/online.html .
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114       Any  typographical  or  formatting  errors that appear in this page are
115       most likely to have been introduced during the conversion of the source
116       files  to  man page format. To report such errors, see https://www.ker‐
117       nel.org/doc/man-pages/reporting_bugs.html .
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121IEEE/The Open Group                  2013                            LDEXP(3P)
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