mirror of https://github.com/mkerrisk/man-pages
157 lines
3.4 KiB
Groff
157 lines
3.4 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\" Distributed under GPL
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.\" Based on glibc infopages
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.TH NEXTAFTER 3 2008-10-06 "GNU" "Linux Programmer's Manual"
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.SH NAME
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nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl \-
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floating-point number manipulation
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.SH SYNOPSIS
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.B #include <math.h>
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.sp
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.BI "double nextafter(double " x ", double " y );
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.br
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.BI "float nextafterf(float " x ", float " y );
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.br
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.BI "long double nextafterl(long double " x ", long double " y );
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.sp
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.BI "double nexttoward(double " x ", long double " y );
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.br
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.BI "float nexttowardf(float " x ", long double " y );
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.br
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.BI "long double nexttowardl(long double " x ", long double " y );
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.sp
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.ad l
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.BR nextafter ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR nextafterf (),
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.BR nextafterl ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR nexttoward (),
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.BR nexttowardf (),
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.BR nexttowardl ():
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE;
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.I cc\ -std=c99
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.ad b
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.SH DESCRIPTION
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The
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.BR nextafter ()
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functions return the next representable floating-point value following
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.I x
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in the direction of
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.IR y .
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If
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.I y
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is less than
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.IR x ,
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these functions will return the largest representable number less than
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.IR y .
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If \fIx\fP equals \fIy\fP, the functions return \fIy\fP.
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The
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.BR nexttoward ()
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functions do the same as the
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.BR nextafter ()
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functions, except that they have a
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.I "long double"
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second argument.
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.SH RETURN VALUE
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On success,
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these functions return the next representable floating-point value after
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.I x
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in the direction of
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.IR y .
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If
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.I x
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equals
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.IR y ,
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then
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.I y
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(cast to the same type as
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.IR x )
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is returned.
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If
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.I x
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or
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.I y
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is a NaN,
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a NaN is returned.
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If
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.I x
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is finite,
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.\" e.g., DBL_MAX
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and the result would overflow,
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a range error occurs,
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and the functions return
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.BR HUGE_VAL ,
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.BR HUGE_VALF ,
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or
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.BR HUGE_VALL ,
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respectively, with the correct mathematical sign.
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If
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.I x
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is not equal to
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.IR y ,
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and the correct function result would be subnormal, zero, or underflow,
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a range error occurs,
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and either the correct value (if it can be represented),
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or 0.0, is returned.
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.SH ERRORS
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See
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.BR math_error (7)
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for information on how to determine whether an error has occurred
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when calling these functions.
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.PP
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The following errors can occur:
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.TP
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Range error: result overflow
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.\" e.g., nextafter(DBL_MAX, HUGE_VAL);
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.\" .I errno
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.\" is set to
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.\" .BR ERANGE .
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An overflow floating-point exception
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.RB ( FE_OVERFLOW )
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is raised.
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.TP
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Range error: result is subnormal or underflows
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.\" e.g., nextafter(DBL_MIN, 0.0);
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.\" .I errno
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.\" is set to
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.\" .BR ERANGE .
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An underflow floating-point exception
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.RB ( FE_UNDERFLOW )
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is raised.
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.PP
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These functions do not set
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.IR errno .
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.\" FIXME . Is it intentional that these functions do not set errno?
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.\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6799
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.SH "CONFORMING TO"
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C99, POSIX.1-2001.
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This function is defined in IEC 559 (and the appendix with
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recommended functions in IEEE 754/IEEE 854).
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.SH BUGS
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In glibc version 2.5 and earlier, these functions do not raise an underflow
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floating-point
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.RB ( FE_UNDERFLOW )
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exception when an underflow occurs.
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.SH "SEE ALSO"
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.BR nearbyint (3)
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