1SCALB(3P)                  POSIX Programmer's Manual                 SCALB(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       scalb - load exponent of a radix-independent floating-point number
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SYNOPSIS

15       #include <math.h>
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17       double scalb(double x, double n);
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19

DESCRIPTION

21       The scalb() function shall compute x*r**n, where r is the radix of  the
22       machine's  floating-point  arithmetic.  When  r  is 2, scalb() shall be
23       equivalent to ldexp(). The value of r is FLT_RADIX which is defined  in
24       <float.h>.
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26       An  application  wishing to check for error situations should set errno
27       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these
28       functions.   On return, if errno is non-zero or fetestexcept(FE_INVALID
29       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has
30       occurred.
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RETURN VALUE

33       Upon successful completion, the scalb() function shall return x*r**n.
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35       If x or n is NaN, a NaN shall be returned.
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37       If n is zero, x shall be returned.
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39       If x is ±Inf and n is not -Inf, x shall be returned.
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41       If x is ±0 and n is not +Inf, x shall be returned.
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43       If  x is ±0 and n is +Inf, a domain error shall occur, and either a NaN
44       (if supported), or an implementation-defined value shall be returned.
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46       If x is ±Inf and n is -Inf, a domain error shall occur,  and  either  a
47       NaN  (if  supported),  or  an  implementation-defined  value  shall  be
48       returned.
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50       If the result would cause an overflow, a range error  shall  occur  and
51       ±HUGE_VAL (according to the sign of x) shall be returned.
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53       If  the  correct  value  would cause underflow, and is representable, a
54       range error may occur and the correct value shall be returned.
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56       If the correct value would cause underflow, and is not representable, a
57       range error may occur, and 0.0 shall be returned.
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ERRORS

60       The scalb() function shall fail if:
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62       Domain Error
63              If x is zero and n is +Inf, or x is Inf and n is -Inf.
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65       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
66       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression
67       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid
68       floating-point exception shall be raised.
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70       Range Error
71              The result would overflow.
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73       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
74       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
75       (math_errhandling & MATH_ERREXCEPT)  is  non-zero,  then  the  overflow
76       floating-point exception shall be raised.
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79       The scalb() function may fail if:
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81       Range Error
82              The result underflows.
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84       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
85       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
86       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow
87       floating-point exception shall be raised.
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90       The following sections are informative.
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EXAMPLES

93       None.
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APPLICATION USAGE

96       Applications should use either scalbln(), scalblnf(), or scalblnl()  in
97       preference to this function.
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99       IEEE Std 1003.1-2001 only defines the behavior for the scalb() function
100       when the n argument is an integer, a NaN, or Inf. The behavior of other
101       values for the n argument is unspecified.
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103       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
104       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
105       at least one of them must be non-zero.
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RATIONALE

108       None.
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FUTURE DIRECTIONS

111       None.
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SEE ALSO

114       feclearexcept(),  fetestexcept(),  ilogb(), ldexp(), logb(), scalbln(),
115       the Base Definitions  volume  of  IEEE Std 1003.1-2001,  Section  4.18,
116       Treatment  of  Error  Conditions for Mathematical Functions, <float.h>,
117       <math.h>
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120       Portions of this text are reprinted and reproduced in  electronic  form
121       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
122       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
123       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
124       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
125       event of any discrepancy between this version and the original IEEE and
126       The Open Group Standard, the original IEEE and The Open Group  Standard
127       is  the  referee document. The original Standard can be obtained online
128       at http://www.opengroup.org/unix/online.html .
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132IEEE/The Open Group                  2003                            SCALB(3P)
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