PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl — compute exponent using FLT_RADIX

SYNOPSIS

       #include <math.h>

       double scalbln(double x, long n);
       float scalblnf(float x, long n);
       long double scalblnl(long double x, long n);
       double scalbn(double x, int n);
       float scalbnf(float x, int n);
       long double scalbnl(long double x, int n);

DESCRIPTION

       The functionality described on this reference page is aligned with the ISO C standard. Any
       conflict between the requirements described here and the ISO C standard is  unintentional.
       This volume of POSIX.1‐2017 defers to the ISO C standard.

       These  functions  shall  compute  x * FLT_RADIXn  efficiently,  not  normally by computing
       FLT_RADIXn explicitly.

       An application wishing to check for error situations should set errno  to  zero  and  call
       feclearexcept(FE_ALL_EXCEPT)  before  calling these functions. On return, if errno is non-
       zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is  non-zero,
       an error has occurred.

RETURN VALUE

       Upon successful completion, these functions shall return x * FLT_RADIXn.

       If  the  result  would cause overflow, a range error shall occur and these functions shall
       return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x)  as  appropriate
       for the return type of the function.

       If  the  correct  value would cause underflow, and is not representable, a range error may
       occur, and scalbln(), scalblnf(), scalblnl(), scalbn(),  scalbnf(),  and  scalbnl()  shall
       return  0.0,  or  (if IEC 60559 Floating-Point is not supported) an implementation-defined
       value no greater in magnitude than  DBL_MIN,  FLT_MIN,  LDBL_MIN,  DBL_MIN,  FLT_MIN,  and
       LDBL_MIN, respectively.

       If x is NaN, a NaN shall be returned.

       If x is ±0 or ±Inf, x shall be returned.

       If n is 0, x shall be returned.

       If  the correct value would cause underflow, and is representable, a range error may occur
       and the correct value shall be returned.

ERRORS

       These functions shall fail if:

       Range Error The result overflows.

                   If the integer expression (math_errhandling & MATH_ERRNO)  is  non-zero,  then
                   errno shall be set to [ERANGE].  If the integer expression (math_errhandling &
                   MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception  shall
                   be raised.

       These functions may fail if:

       Range Error The result underflows.

                   If  the  integer  expression (math_errhandling & MATH_ERRNO) is non-zero, then
                   errno shall be set to [ERANGE].  If the integer expression (math_errhandling &
                   MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall
                   be raised.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       On  error,  the  expressions  (math_errhandling  &  MATH_ERRNO)  and  (math_errhandling  &
       MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

RATIONALE

       These functions are named so as to avoid conflicting with the historical definition of the
       scalb() function from the Single UNIX Specification. The difference is  that  the  scalb()
       function has a second argument of double instead of int.  The scalb() function is not part
       of the ISO C standard. The three functions whose second type is long are provided  because
       the  factor  required  to  scale  from  the  smallest positive floating-point value to the
       largest finite one, on many implementations, is too large to  represent  in  the  minimum-
       width int format.

FUTURE DIRECTIONS

       None.

SEE ALSO

       feclearexcept(), fetestexcept()

       The  Base  Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions
       for Mathematical Functions, <math.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1-2017,  Standard  for  Information Technology -- Portable Operating System Interface
       (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C)  2018  by
       the  Institute  of  Electrical  and Electronics Engineers, Inc and The Open Group.  In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .