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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
.\"
.Dd $Mdocdate: April 26 2016 $
.Dt LOGB 3
.Os
.Sh NAME
.Nm logb ,
.Nm logbf ,
.Nm logbl ,
.Nm scalb ,
.Nm scalbf ,
.Nm scalbl ,
.Nm significand ,
.Nm significandf
.Nd IEEE test functions
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn logb "double x"
.Ft float
.Fn logbf "float x"
.Ft long double
.Fn logbl "long double x"
.Ft double
.Fn scalb "double x" "double n"
.Ft float
.Fn scalbf "float x" "float n"
.Ft long double
.Fn scalbl "long double x" "long double n"
.Ft double
.Fn significand "double x"
.Ft float
.Fn significandf "float x"
.Sh DESCRIPTION
These functions allow users to test conformance to
.St -ieee754 .
Their use is not otherwise recommended.
.Pp
.Fn logb x
returns
.Fa x Ns 's exponent
.Fa n ,
a signed integer converted to double\-precision floating\-point.
.Fn logb \(+-infinity
= +infinity;
.Fn logb 0
= -infinity with a division by zero exception.
.Fn logbf
is the single precision form of
.Fn logb .
.Fn logbl
is the extended precision form of
.Fn logb .
.Pp
.Fn scalb x n
returns
.Fa x Ns *(2** Ns Fa n )
computed by exponent manipulation.
.Fn scalbf
is the single precision form of
.Fn scalb .
.Fn scalbl
is the extended precision form of
.Fn scalb .
.Pp
.Fn significand x
returns
.Fa sig ,
where
.Fa x
:=
.Fa sig No * 2** Ns Fa n
with 1 \(<=
.Fa sig
< 2.
.Fn significand x
is not defined when
.Fa x
is 0, \(+-infinity, or NaN.
.Fn significandf
is the single precision for of
.Fn significand .
.Sh SEE ALSO
.Xr fpclassify 3 ,
.Xr ilogb 3 ,
.Xr scalbn 3
.Sh STANDARDS
.St -ieee754