The functions described in this section are primarily provided as a way
to efficiently perform certain low-level manipulations on floating point
numbers that are represented internally using a binary radix;
see Floating Point Concepts. These functions are required to
have equivalent behavior even if the representation does not use a radix
of 2, but of course they are unlikely to be particularly efficient in
those cases.

All these functions are declared in math.h.

— Function: double frexp (double value, int *exponent)

— Function: float frexpf (float value, int *exponent)

— Function: long double frexpl (long double value, int *exponent)

These functions are used to split the number value
into a normalized fraction and an exponent.

If the argument value is not zero, the return value is value
times a power of two, and is always in the range 1/2 (inclusive) to 1
(exclusive). The corresponding exponent is stored in
*exponent; the return value multiplied by 2 raised to this
exponent equals the original number value.

For example, frexp (12.8, &exponent) returns 0.8 and
stores 4 in exponent.

If value is zero, then the return value is zero and
zero is stored in *exponent.

— Function: double ldexp (double value, int exponent)

— Function: float ldexpf (float value, int exponent)

— Function: long double ldexpl (long double value, int exponent)

These functions return the result of multiplying the floating-point
number value by 2 raised to the power exponent. (It can
be used to reassemble floating-point numbers that were taken apart
by frexp.)

For example, ldexp (0.8, 4) returns 12.8.

The following functions, which come from BSD, provide facilities
equivalent to those of ldexp and frexp. See also the
ISO C function logb which originally also appeared in BSD.

— Function: double scalb (double value, int exponent)

— Function: float scalbf (float value, int exponent)

— Function: long double scalbl (long double value, int exponent)

The scalb function is the BSD name for ldexp.

— Function: long long int scalbn (double x, int n)

— Function: long long int scalbnf (float x, int n)

— Function: long long int scalbnl (long double x, int n)

scalbn is identical to scalb, except that the exponent
n is an int instead of a floating-point number.

— Function: long long int scalbln (double x, long int n)

— Function: long long int scalblnf (float x, long int n)

— Function: long long int scalblnl (long double x, long int n)

scalbln is identical to scalb, except that the exponent
n is a long int instead of a floating-point number.

— Function: long long int significand (double x)

— Function: long long int significandf (float x)

— Function: long long int significandl (long double x)

significand returns the mantissa of x scaled to the range
[1, 2).
It is equivalent to scalb (x, (double) -ilogb (x)).

This function exists mainly for use in certain standardized tests
of IEEE 754 conformance.

Published under the terms of the GNU General Public License