scalbln(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SCALBLN(3P)             POSIX Programmer's Manual            SCALBLN(3P)

PROLOG         top

       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         top

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

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       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         top

       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         top

       None.

SEE ALSO         top

       feclearexcept(3p), fetestexcept(3p)

       The Base Definitions volume of POSIX.1‐2017, Section 4.20,
       Treatment of Error Conditions for Mathematical Functions,
       math.h(0p)

COPYRIGHT         top

       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 .

IEEE/The Open Group               2017                       SCALBLN(3P)

Pages that refer to this page: math.h(0p)ilogb(3p)logb(3p)