nextafter.3p (5345B)
- '\" et
- .TH NEXTAFTER "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- nextafter,
- nextafterf,
- nextafterl,
- nexttoward,
- nexttowardf,
- nexttowardl
- \(em next representable floating-point number
- .SH SYNOPSIS
- .LP
- .nf
- #include <math.h>
- .P
- double nextafter(double \fIx\fP, double \fIy\fP);
- float nextafterf(float \fIx\fP, float \fIy\fP);
- long double nextafterl(long double \fIx\fP, long double \fIy\fP);
- double nexttoward(double \fIx\fP, long double \fIy\fP);
- float nexttowardf(float \fIx\fP, long double \fIy\fP);
- long double nexttowardl(long double \fIx\fP, long double \fIy\fP);
- .fi
- .SH DESCRIPTION
- The functionality described on this reference page is aligned with the
- ISO\ C standard. Any conflict between the requirements described here and the
- ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
- .P
- The
- \fInextafter\fR(),
- \fInextafterf\fR(),
- and
- \fInextafterl\fR()
- functions shall compute the next representable floating-point value
- following
- .IR x
- in the direction of
- .IR y .
- Thus, if
- .IR y
- is less than
- .IR x ,
- \fInextafter\fR()
- shall return the largest representable floating-point number less than
- .IR x .
- The
- \fInextafter\fR(),
- \fInextafterf\fR(),
- and
- \fInextafterl\fR()
- functions shall return
- .IR y
- if
- .IR x
- equals
- .IR y .
- .P
- The
- \fInexttoward\fR(),
- \fInexttowardf\fR(),
- and
- \fInexttowardl\fR()
- functions shall be equivalent to the corresponding
- \fInextafter\fR()
- functions, except that the second parameter shall have type
- .BR "long double"
- and the functions shall return
- .IR y
- converted to the type of the function if
- .IR x
- equals
- .IR y .
- .P
- An application wishing to check for error situations should set
- .IR errno
- to zero and call
- .IR feclearexcept (FE_ALL_EXCEPT)
- before calling these functions. On return, if
- .IR errno
- is non-zero or \fIfetestexcept\fR(FE_INVALID | FE_DIVBYZERO |
- FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.
- .SH "RETURN VALUE"
- Upon successful completion, these functions shall return the next
- representable floating-point value following
- .IR x
- in the direction of
- .IR y .
- .P
- If
- .IR x ==\c
- .IR y ,
- .IR y
- (of the type
- .IR x )
- shall be returned.
- .P
- If
- .IR x
- is finite and the correct function value would overflow, a range error
- shall occur and \(+-HUGE_VAL, \(+-HUGE_VALF, and \(+-HUGE_VALL (with
- the same sign as
- .IR x )
- shall be returned as appropriate for the return type of the function.
- .P
- If
- .IR x
- or
- .IR y
- is NaN, a NaN shall be returned.
- .P
- If
- .IR x !=\c
- .IR y
- and the correct function value is subnormal, zero, or underflows,
- a range error shall occur, and
- .br
- the correct function value (if representable) or
- .br
- 0.0 shall be returned.
- .SH ERRORS
- These functions shall fail if:
- .IP "Range\ Error" 12
- The correct value overflows.
- .RS 12
- .P
- If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
- non-zero, then
- .IR errno
- shall be set to
- .BR [ERANGE] .
- If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
- non-zero, then the overflow floating-point exception shall be raised.
- .RE
- .IP "Range\ Error" 12
- The correct value is subnormal or underflows.
- .RS 12
- .P
- If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
- non-zero, then
- .IR errno
- shall be set to
- .BR [ERANGE] .
- If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
- non-zero, then the underflow floating-point exception shall be raised.
- .RE
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- None.
- .SH "APPLICATION USAGE"
- On error, the expressions (\fImath_errhandling\fR & MATH_ERRNO) and
- (\fImath_errhandling\fR & MATH_ERREXCEPT) are independent of each
- other, but at least one of them must be non-zero.
- .P
- When
- .IR <tgmath.h>
- is included, note that the return type of
- \fInextafter\fR()
- depends on the generic typing deduced from both arguments, while the
- return type of
- \fInexttoward\fR()
- depends only on the generic typing of the first argument.
- .SH RATIONALE
- None.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIfeclearexcept\fR\^(\|)",
- .IR "\fIfetestexcept\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 4.20" ", " "Treatment of Error Conditions for Mathematical Functions",
- .IR "\fB<math.h>\fP",
- .IR "\fB<tgmath.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .