*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->Tru64 Unix man pages -> logb (3)              



NAME    [Toc]    [Back]

       frexp, ldexp, logb, scalb - Manipulate floating-point numbers

SYNOPSIS    [Toc]    [Back]

       #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 );

LIBRARY    [Toc]    [Back]

       Math Library (libm)

STANDARDS    [Toc]    [Back]

       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.

DESCRIPTION    [Toc]    [Back]

       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

       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

[ Back ]
 Similar pages
Name OS Title
frexp IRIX manipulate parts of floating-point numbers (libc routines)
isgreaterequal FreeBSD compare two floating-point numbers
isgreater FreeBSD compare two floating-point numbers
isless FreeBSD compare two floating-point numbers
islessgreater FreeBSD compare two floating-point numbers
isunordered FreeBSD compare two floating-point numbers
islessequal FreeBSD compare two floating-point numbers
fpgetmask IRIX floating-point units
glcgetf IRIX return value of a specified floating point variable
fpgetround FreeBSD IEEE floating point interface
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service