minix/lib/libm/man/ieee.3

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.\" from: @(#)ieee.3 6.4 (Berkeley) 5/6/91
.\" $NetBSD: ieee.3,v 1.21 2010/09/15 16:11:30 christos Exp $
.\"
.Dd February 25, 1994
.Dt IEEE 3
.Os
.Sh NAME
.Nm copysign ,
.Nm copysignf ,
.Nm copysignl ,
.Nm finite ,
.Nm finitef ,
.Nm ilogb ,
.Nm ilogbf ,
.Nm nextafter ,
.Nm nextafterf ,
.Nm nextafterl ,
.Nm nexttoward ,
.Nm remainder ,
.Nm remainderf ,
.Nm scalbn ,
.Nm scalbnf
.Nd functions for IEEE arithmetic
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.Ft double
.Fn copysign "double x" "double y"
.Ft float
.Fn copysignf "float x" "float y"
.Ft long double
.Fn copysignl "long double x" "long double y"
.Ft int
.Fn finite "double x"
.Ft int
.Fn finitef "float x"
.Ft int
.Fn ilogb "double x"
.Ft int
.Fn ilogbf "float x"
.Ft double
.Fn nextafter "double x" "double y"
.Ft float
.Fn nextafterf "float x" "float y"
.Ft long double
.Fn nextafterl "long double x" "long double y"
.Ft double
.Fn nexttoward "double x" "long double y"
.Ft double
.Fn remainder "double x" "double y"
.Ft float
.Fn remainderf "float x" "float y"
.Ft double
.Fn scalbn "double x" "int n"
.Ft float
.Fn scalbnf "float x" "int n"
.Sh DESCRIPTION
These functions are required or recommended by
.St -ieee754 .
.Pp
.Fn copysign
returns
.Fa x
with its sign changed to
.Fa y Ns 's .
.Pp
.Fn finite
returns the value 1 just when
\-\*(If \*(Lt
.Fa x
\*(Lt +\*(If;
otherwise a
zero is returned
(when
.Pf \*(Ba Ns Fa x Ns \*(Ba
= \*(If or
.Fa x
is \*(Na).
.Pp
.Fn ilogb
returns
.Fa x Ns 's exponent
.Fa n ,
in integer format.
.Fn ilogb \*(Pm\*(If
returns
.Dv INT_MAX
and
.Fn ilogb 0
returns
.Dv INT_MIN .
.Pp
.Fn nextafter
returns the next machine representable number from
.Fa x
in direction
.Fa y .
.Pp
.Fn nexttoward
is equivalent to
.Fn nextafter ,
except that the second parameter has type
.Ft long double
and the function returns
.Dv y
converted to the type of the function if
.Dv x
equals
.Dv y .
.Pp
.Fn remainder
returns the remainder
.Fa r
:=
.Fa x
\-
.Fa n\(**y
where
.Fa n
is the integer nearest the exact value of
.Bk -words
.Fa x Ns / Ns Fa y ;
.Ek
moreover if
.Pf \*(Ba Fa n
\-
.Sm off
.Fa x No / Fa y No \*(Ba
.Sm on
=
1/2
then
.Fa n
is even.
Consequently the remainder is computed exactly and
.Sm off
.Pf \*(Ba Fa r No \*(Ba
.Sm on
\*(Le
.Sm off
.Pf \*(Ba Fa y No \*(Ba/2 .
.Sm on
But
.Fn remainder x 0
and
.Fn remainder \*(If 0
are invalid operations that produce a \*(Na.
.Pp
.Fn scalbn
returns
.Fa x Ns \(**(2** Ns Fa n )
computed by exponent manipulation.
.Sh SEE ALSO
.Xr math 3
.Sh STANDARDS
.St -ieee754
.Sh HISTORY
The
.Nm ieee
functions appeared in
.Bx 4.3 .