Manpages - scalb.3

scalb, scalbf, scalbl - multiply floating-point number by integral power of radix (OBSOLETE)

  #include <math.h>

  double scalb(double x, double exp);
  float scalbf(float x, float exp);
  long double scalbl(long double x, long double exp);

Link with -lm.

Feature Test Macro Requirements for glibc (see *feature_test_macros*(7)):

*scalb*():

      _XOPEN_SOURCE >= 500
          || /* Since glibc 2.19: */ _DEFAULT_SOURCE
          || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

*scalbf*(), *scalbl*():

      _XOPEN_SOURCE >= 600
          || /* Since glibc 2.19: */ _DEFAULT_SOURCE
          || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

These functions multiply their first argument x by FLT_RADIX (probably 2) to the power of exp, that is:

      x * FLT_RADIX ** exp

The definition of FLT_RADIX can be obtained by including <float.h>.

On success, these functions return x * FLT_RADIX ** exp.

If x or exp is a NaN, a NaN is returned.

If x is positive infinity (negative infinity), and exp is not negative infinity, positive infinity (negative infinity) is returned.

If x is +0 (-0), and exp is not positive infinity, +0 (-0) is returned.

If x is zero, and exp is positive infinity, a domain error occurs, and a NaN is returned.

If x is an infinity, and exp is negative infinity, a domain error occurs, and a NaN is returned.

If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with a sign the same as x.

If the result underflows, a range error occurs, and the functions return zero, with a sign the same as x.

See *math_error*(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

• Domain error: x is 0, and exp is positive infinity, or x is positive infinity and exp is negative infinity and the other argument is not a NaN :: errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.
• errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised.
• errno is set to ERANGE. An underflow floating-point exception (FE_UNDERFLOW) is raised.

For an explanation of the terms used in this section, see *attributes*(7).

*scalb*() is specified in POSIX.1-2001, but marked obsolescent. POSIX.1-2008 removes the specification of *scalb*(), recommending the use of *scalbln*(3), *scalblnf*(3), or *scalblnl*(3) instead. The *scalb*() function is from 4.3BSD.

*scalbf*() and *scalbl*() are unstandardized; *scalbf*() is nevertheless present on several other systems

Before glibc 2.20, these functions did not set errno for domain and range errors.

*ldexp*(3), *scalbln*(3)

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