exp2f(3p)

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.
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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

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

32       Upon successful completion, these functions shall return 2**x.
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34       If the correct value would cause overflow, a range  error  shall  occur
35       and  exp2(),  exp2f(),  and exp2l() shall return the value of the macro
36       HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
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38       If the correct value would cause underflow, and is not representable, a
39       range  error may occur, and  either 0.0 (if supported), or an implemen‐
40       tation-defined value shall be returned.
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42       If x is NaN, a NaN shall be returned.
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44       If x is ±0, 1 shall be returned.
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46       If x is -Inf, +0 shall be returned.
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48       If x is +Inf, x shall be returned.
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50       If the correct value would cause underflow,  and  is  representable,  a
51       range error may occur and the correct value shall be returned.
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ERRORS

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

79       None.
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APPLICATION USAGE

82       For  IEEE Std 754-1985  double,  1024  <=  x implies exp2( x) has over‐
83       flowed. The value x < -1022 implies exp( x) has underflowed.
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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.
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RATIONALE

90       None.
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FUTURE DIRECTIONS

93       None.
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COPYRIGHT

101       Portions of this text are reprinted and reproduced in  electronic  form
102       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
103       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
104       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
105       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
106       event of any discrepancy between this version and the original IEEE and
107       The Open Group Standard, the original IEEE and The Open Group  Standard
108       is  the  referee document. The original Standard can be obtained online
109       at http://www.opengroup.org/unix/online.html .
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113IEEE/The Open Group                  2003                             EXP2(3P)