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\" Copyright (c) 2011 Jukka Ruohonen <
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Dd August 22, 2016
Dt ILOGB 3
Os
Sh NAME
Nm ilogb ,
Nm ilogbf ,
Nm ilogbl
Nd an unbiased 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"
Sh DESCRIPTION
The
Fn ilogb ,
Fn ilogbf ,
and
Fn ilogbl
functions return the exponent of the non-zero real floating-point number
Fa x
as a signed integer value.
Formally the return value is the integral part of
Bd -ragged -offset indent
log_r |
Va x | ,
Ed
Pp
where
Fa r
is the radix of the machine's floating-point arithmetic defined by the
Dv FLT_RADIX
constant in
In float.h .
Sh RETURN VALUES
As described above, upon successful completion,
the functions return the exponent.
Functionally this is the same as calling the corresponding
Xr logb 3
function and casting the return value to
Vt int .
Pp
The following special cases may occur:
Bl -enum -offset indent
It
If
Fa x
is zero, the value of
Dv FP_ILOGB0
is returned and a domain error occurs.
It
If
Fa x
is infinite, a domain error occurs and the value of
Dv INT_MAX
is returned.
It
If
Fa x
is \*(Na, a domain error is raised and the value of
Dv FP_ILOGBNAN
is returned.
It
If the correct value is outside the range of the return type,
a domain error occurs but an unspecified value is returned.
El
Sh SEE ALSO
Xr ilog2 3 ,
Xr logb 3 ,
Xr math 3
Sh STANDARDS
The described functions conform to
St -isoC-99 .
