'\" te
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.TH nextafter 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
.SH NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl \- next
representable double-precision floating-point number
.SH SYNOPSIS
.LP
.nf
c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBdouble\fR \fBnextafter\fR(\fBdouble\fR \fIx\fR, \fBdouble\fR \fIy\fR);
.fi

.LP
.nf
\fBfloat\fR \fBnextafterf\fR(\fBfloat\fR \fIx\fR, \fBfloat\fR \fIy\fR);
.fi

.LP
.nf
\fBlong double\fR \fBnextafterl\fR(\fBlong double\fR \fIx\fR, \fBlong double\fR \fIy\fR);
.fi

.LP
.nf
\fBdouble\fR \fBnexttoward\fR(\fBdouble\fR \fIx\fR, \fBlong double\fR \fIy\fR);
.fi

.LP
.nf
\fBfloat\fR \fBnexttowardf\fR(\fBfloat\fR \fIx\fR, \fBlong double\fR \fIy\fR);
.fi

.LP
.nf
\fBlong double\fR \fBnexttowardl\fR(\fBlong double\fR \fIx\fR, \fBlong double\fR \fIy\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBnextafter()\fR, \fBnextafterf()\fR, and \fBnextafterl()\fR functions
compute the next representable floating-point value following \fIx\fR in the
direction of \fIy\fR. Thus, if \fIy\fR is less than \fIx\fR, \fBnextafter()\fR
returns the largest representable floating-point number less than \fIx\fR. The
\fBnextafter()\fR, \fBnextafterf()\fR, and \fBnextafterl()\fR functions return
\fIy\fR if \fIx\fR equals \fIy\fR.
.sp
.LP
The \fBnexttoward()\fR, \fBnexttowardf()\fR, and \fBnexttowardl()\fR functions
are equivalent to the corresponding \fBnextafter()\fR functions, except that
the second parameter has type \fBlong double\fR and the functions return
\fIy\fR converted to the type of the function if \fIx\fR equals \fIy\fR.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, these functions return the next representable
floating-point value following \fIx\fR in the direction of \fIy\fR.
.sp
.LP
If \fIx\fR == \fIy\fR, \fIy\fR (of the type \fIx\fR) is returned.
.sp
.LP
If \fIx\fR is finite and the correct function value would overflow, a range
error occurs and \(+-\fBHUGE_VAL\fR, \(+-\fBHUGE_VALF\fR, and
\(+-\fBHUGE_VALL\fR (with the same sign as \fIx\fR) is returned as appropriate
for the return type of the function.
.sp
.LP
If \fIx\fR or \fIy\fR is NaN, a NaN is returned.
.sp
.LP
If \fIx\fR != \fIy\fR and the correct function value is subnormal, zero, or
underflows, a range error occurs and either the correct function value (if
representable) or 0.0 is returned.
.SH ERRORS
.sp
.LP
These functions will fail if:
.sp
.ne 2
.mk
.na
\fBRange Error\fR
.ad
.RS 15n
.rt  
The correct value overflows.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, the overflow floating-point exception is raised.
.sp
The \fBnextafter()\fR function sets \fBerrno\fR to \fBERANGE\fR if the correct
value would overflow.
.RE

.sp
.ne 2
.mk
.na
\fBRange Error\fR
.ad
.RS 15n
.rt  
The correct value underflows.
.sp
If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
non-zero, the underflow floating-point exception is raised.
.RE

.SH USAGE
.sp
.LP
An application wanting to check for exceptions should call
\fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
\fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
raised. An application should either examine the return value or check the
floating point exception flags to detect exceptions.
.sp
.LP
An application can also set \fBerrno\fR to 0 before calling \fBnextafter()\fR.
On return, if \fBerrno\fR is non-zero, an error has occurred. The
\fBnextafterf()\fR, \fBnextafterl()\fR. \fBnexttoward()\fR,
\fBnexttowardf()\fR, and \fBnexttowardl()\fR functions do not set \fBerrno\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityStandard
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M), \fBmath.h\fR(3HEAD),
\fBattributes\fR(5), \fBstandards\fR(5)