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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd September 13, 2015
.Dt NEXTAFTER 3
.Os
.Sh NAME
.Nm nextafter ,
.Nm nextafterf ,
.Nm nextafterl ,
.Nm nexttoward ,
.Nm nexttowardf ,
.Nm nexttowardl
.Nd next representable floating-point number
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In math.h
.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 float
.Fn nexttowardf "float x" "long double y"
.Ft long double
.Fn nexttowardl "long double x" "long double y"
.Sh DESCRIPTION
The
.Fn nextafter ,
.Fn nextafterf ,
and
.Fn nextafterl
functions return the next machine representable number from
.Fa x
in direction of
.Fa y .
In other words, if
.Fa y
is less than
.Fa x ,
the functions return the largest representable floating-point number less than
.Fa x .
When
.Fa x
equals
.Fa y ,
the value of
.Fa y
is returned.
The three functions differ only in the type of the return value and
.Fa x .
.Pp
The
.Fn nexttoward
and
.Fn nexttowardf
functions are equivalent to the
.Fn nextafter
family of functions with two exceptions:
.Bl -enum -offset indent
.It
The second parameter has a type
.Vt long double .
.It
The return value is
.Fa y
converted to the type of the function, provided that
.Fa x
equals
.Fa y .
.El
.Pp
.Fn nexttowardl
is equivalent to
.Fn nextafterl .
.Sh RETURN VALUES
Upon successful completion, the described functions return
the next representable floating-point value as described above.
If
.Fa x
is finite but an overflow would occur,
a range error follows and the functions return
.Dv \*(PmHUGE_VAL ,
.Dv \*(PmHUGE_VALF ,
or
.Dv \*(PmHUGE_VALL
with the same sign as
.Fa x .
When either
.Fa x
or
.Fa y
is \*(Na, a \*(Na is returned.
When
.Fa x
is not
.Fa y
but the function value is subnormal, zero, or underflows,
a range error occurs, and either 0.0 or the correct function
value (if representable) is returned.
.Sh SEE ALSO
.Xr math 3
.Sh STANDARDS
The described functions conform to
.St -isoC-99 .