1EXP2(3P)                   POSIX Programmer's Manual                  EXP2(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.
10

NAME

12       exp2, exp2f, exp2l — exponential base 2 functions
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SYNOPSIS

15       #include <math.h>
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17       double exp2(double x);
18       float exp2f(float x);
19       long double exp2l(long double x);
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DESCRIPTION

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.
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27       These functions shall compute the base-2 exponential of x.
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29       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.
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RETURN VALUE

36       Upon successful completion, these functions shall return 2x.
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38       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.
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42       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.
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48       If x is NaN, a NaN shall be returned.
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50       If x is ±0, 1 shall be returned.
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52       If x is -Inf, +0 shall be returned.
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54       If x is +Inf, 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       exp(), feclearexcept(), fetestexcept(), isnan(), log()
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99       The Base Definitions volume of POSIX.1‐2017, Section 4.20, 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 1003.1-2017, 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
113       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 .
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120IEEE/The Open Group                  2017                             EXP2(3P)
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