frexp, ldexp, logb, scalb - Manipulate floating-point numbers
#include <math.h>
double frexp(
double x,
int *n ); float frexpf(
float x,
int *n ); long double frexpl(
long double x,
int *n ); double ldexp(
double y,
int n ); float ldexpf(
float y,
int n ); long double ldexpl(
long double y,
int n ); double logb(
double x ); float logbf(
float x ); long double logbl(
long double x ); double scalb(
double x,
double n ); float scalbf(
float x,
float n ); long double scalbl(
long double x,
long double n );
Math Library (libm)
Interfaces documented on this reference page conform to
industry standards as follows:
frexp(): XPG4
ldexp(): XPG4
logb(): XPG4-UNIX
scalb(): XPG4-UNIX
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Every nonzero number can be written uniquely as the normalized
mantissa (fraction) z times 2 raised to the power
p, where the absolute value of z is in the range [0.5,
1.0), and the exponent p, is an integer.
The frexp(), frexpf(), and frexpl() functions break a
floating-point number into a normalized fraction and an
integral power of 2. The functions store the integer in
the int object pointed to by the n parameter and return
the fraction part.
The ldexp(), ldexpf(), and ldexpl() functions multiply a
floating-point number, y, by an integral power of 2.
The logb(), logbf(), and logbl() functions return a signed
integer converted to double-precision floating-point and
so chosen that 1 <= |x|/2**n < 2 unless x = 0 or |x| =
infinity or x lies between 0 and the Underflow Threshold.
IEEE 754 defines logb(+infinity) = +infinity and logb(0) =
-infinity. The latter is required to signal Division-byZero.
The scalb(), scalbf(), and scalbl() functions are defined
as x*(2**n) for integer n.
The following table describes function behavior in
response to exceptional arguments:
--------------------------------------------------------------------------
Function Exceptional Argument Routine Behavior
--------------------------------------------------------------------------
frexp(), frexpf(), frexpl() |x| = infinity Invalid argument
logb(), logbf(), logbl() |x| = infinity Invalid argument
scalb(), scalbf(), scalbl() x*(2**n) > max_float Overflow
scalb(), scalbf(), scalbl() x*(2**n) < min_float Underflow
ldexp(), ldexpf(), ldexpl() x*(2**n) > max_float Overflow
ldexp(), ldexpf(), ldexpl() x*(2**n) < min_float Underflow
--------------------------------------------------------------------------
The following table lists boundary values used by these
functions:
--------------------------------------------------------------------
Value Name Data Type Hexadecimal Value Decimal Value
--------------------------------------------------------------------
max_float S_FLOAT 7F7FFFFF 3.402823e38
T_FLOAT 7FEFFFFFFFFFFFFF 1.797693134862316e308
min_float S_FLOAT 00000001 1.4012985e-45
T_FLOAT 0000000000000001 4.940656458412465e-324
--------------------------------------------------------------------
frexp(3)
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