xref: /freebsd/lib/msun/man/ilogb.3 (revision fbbd9655e5107c68e4e0146ff22b73d7350475bc)

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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
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.Dd December 16, 2007
.Dt ILOGB 3
.Os
.Sh NAME
.Nm ilogb ,
.Nm ilogbf ,
.Nm ilogbl ,
.Nm logb ,
.Nm logbf ,
.Nm logbl
.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"
.Ft long double
.Fn logbl "long double 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 ,
.Fn logbf x ,
and
.Fn logbl 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 ,
.Fn logbf ,
and
.Fn logbl
routines conform to
.St -isoC-99 .
The latter three
implement the logb function recommended by
.St -ieee754 .
.Sh HISTORY
.Bl -tag -width "Function " -compact
.It Em Function
.Em "First Appeared In"
.It Fn logb
.Bx 4.3
.It Fn ilogb
.Fx 1.1.5
.It Fn ilogbf
.Fx 2.0
.It Fn logbf
.Fx 2.0
.It Fn ilogbl
.Fx 5.4
.It Fn logbl
.Fx 8.0
.El