2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "NEXTAFTER" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" nextafter
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl
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\- next representable floating-point
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number
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.SH SYNOPSIS
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.LP
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\fB#include <math.h>
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.br
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.sp
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double nextafter(double\fP \fIx\fP\fB, double\fP \fIy\fP\fB);
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.br
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float nextafterf(float\fP \fIx\fP\fB, float\fP \fIy\fP\fB);
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.br
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long double nextafterl(long double\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);
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.br
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double nexttoward(double\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);
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.br
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float nexttowardf(float\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);
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.br
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long double nexttowardl(long double\fP \fIx\fP\fB, long double\fP
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\fIy\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fInextafter\fP(), \fInextafterf\fP(), and \fInextafterl\fP()
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functions shall compute the next representable
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floating-point value following \fIx\fP in the direction of \fIy\fP.
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Thus, if \fIy\fP is less than \fIx\fP, \fInextafter\fP()
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shall return the largest representable floating-point number less
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than \fIx\fP. The \fInextafter\fP(), \fInextafterf\fP(), and
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\fInextafterl\fP() functions shall return \fIy\fP if \fIx\fP equals
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\fIy\fP.
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.LP
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The \fInexttoward\fP(), \fInexttowardf\fP(), and \fInexttowardl\fP()
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functions shall be equivalent to the corresponding
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\fInextafter\fP() functions, except that the second parameter shall
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have type \fBlong double\fP and the functions shall return
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\fIy\fP converted to the type of the function if \fIx\fP equals \fIy\fP.
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.LP
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An application wishing to check for error situations should set \fIerrno\fP
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to zero and call
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\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
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On return, if \fIerrno\fP is non-zero or
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\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
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is non-zero, an error has occurred.
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.SH RETURN VALUE
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.LP
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Upon successful completion, these functions shall return the next
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representable floating-point value following \fIx\fP in the
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direction of \fIy\fP.
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.LP
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If \fIx\fP== \fIy\fP, \fIy\fP (of the type \fIx\fP) shall be returned.
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.LP
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If \fIx\fP is finite and the correct function value would overflow,
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a range error shall occur and \(+-HUGE_VAL,
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\(+-HUGE_VALF, and \(+-HUGE_VALL (with the same sign as \fIx\fP) shall
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be returned as appropriate for the return type of
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the function.
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.LP
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If
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\fIx\fP or \fIy\fP is NaN, a NaN shall be returned.
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.LP
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If \fIx\fP!= \fIy\fP and the correct function value is subnormal,
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zero, or underflows, a range error shall occur, and either
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the correct function value (if representable) or 0.0 shall be returned.
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.SH ERRORS
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.LP
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These functions shall fail if:
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.TP 7
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Range\ Error
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The correct value overflows.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the overflow floating-point exception shall be
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raised.
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.TP 7
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Range\ Error
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The correct value is subnormal or underflows.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the underflow floating-point exception shall be
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raised.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
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& MATH_ERREXCEPT) are independent of
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each other, but at least one of them must be non-zero.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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2007-09-20 06:11:55 +00:00
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\fIfeclearexcept\fP(), \fIfetestexcept\fP(), the Base
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2004-11-03 13:51:07 +00:00
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Definitions volume of IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment
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of
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Error Conditions for Mathematical Functions, \fI<math.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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