xref: /freebsd/lib/msun/man/ilogb.3 (revision 32948b81c442618246906e6cbc40da567fda00a6)

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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
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.Dd Nov 6, 2005
.Dt ILOGB 3
.Os
.Sh NAME
.Nm ilogb ,
.Nm ilogbf ,
.Nm ilogbl ,
.Nm logb ,
.Nm logbf
.Nd extract exponent
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft int
.Fn ilogb "double x"
.Ft int
.Fn ilogbf "float x"
.Ft int
.Fn ilogbl "long double x"
.Ft double
.Fn logb "double x"
.Ft float
.Fn logbf "float x"
.Sh DESCRIPTION
.Fn ilogb ,
.Fn ilogbf
and
.Fn ilogbl
return
.Fa x Ns 's exponent
in integer format.
.Fn ilogb \*(Pm\*(If
returns
.Dv INT_MAX ,
.Fn ilogb \*(Pm\*(Na
returns
.Dv FP_ILOGBNAN ,
and
.Fn ilogb 0
returns
.Dv FP_ILOGB0 .
.Pp
.Fn logb x
and
.Fn logbf x
return
.Fa x Ns 's exponent
in floating\-point format with the same precision as
.Fa x .
.Fn logb \*(Pm\*(If
returns +\*(If, and
.Fn logb 0
returns -\*(If with a division by zero exception.
.Sh SEE ALSO
.Xr frexp 3 ,
.Xr ieee 3 ,
.Xr math 3 ,
.Xr scalbn 3
.Sh STANDARDS
The
.Fn ilogb ,
.Fn ilogbf ,
.Fn ilogbl ,
.Fn logb
and
.Fn logbf
routines conform to
.St -isoC-99 .
.Fn logb
and
.Fn logbf
implement the logb function recommended by
.St -ieee754 .
.Sh HISTORY
The
.Fn logb
function appeared in
.Bx 4.3 .
The
.Fn ilogb
function appeared in
.Fx 1.1.5 .
The
.Fn ilogbf
and
.Fn logbf
functions appeared in
.Fx 2.0 .
The
.Fn ilogbl
function appeared in
.Fx 5.4 .