xref: /freebsd/lib/msun/man/ieee.3 (revision 24a0682c6465290759ed0b09ea16e40e7cd47053)

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.\"     from: @(#)ieee.3	6.4 (Berkeley) 5/6/91
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.Dd June 20, 2004
.Dt IEEE 3
.Os
.Sh NAME
.Nm copysign ,
.Nm copysignf ,
.Nm copysignl ,
.Nm finite ,
.Nm finitef ,
.Nm ilogb ,
.Nm ilogbf ,
.Nm ilogbl ,
.Nm nextafter ,
.Nm nextafterf ,
.Nm remainder ,
.Nm remainderf ,
.Nm scalbln ,
.Nm scalblnf ,
.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 int
.Fn ilogbl "long double x"
.Ft double
.Fn nextafter "double x" "double y"
.Ft float
.Fn nextafterf "float x" "float y"
.Ft double
.Fn remainder "double x" "double y"
.Ft float
.Fn remainderf "float x" "float y"
.Ft double
.Fn scalbln "double x" "long n"
.Ft float
.Fn scalblnf "float x" "long n"
.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
The
.Fn copysign ,
.Fn copysignf
and
.Fn copysignl
functions
return
.Fa x
with its sign changed to
.Fa y Ns 's .
.Pp
.Fn finite
and
.Fn finitef
return 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 ,
.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 nextafter
and
.Fn nextafterf
return the next machine representable number from
.Fa x
in direction
.Fa y .
.Pp
.Fn remainder
and
.Fn remainderf
return 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 scalbln ,
.Fn scalblnf ,
.Fn scalbn ,
and
.Fn scalbnf
return
.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 .
The
.Fn copysignl ,
.Fn scalbln ,
and
.Fn scalblnf
functions first appeared in
.Fx 5.3 .