PROLOG  NAME  SYNOPSIS  DESCRIPTION  RETURN VALUE  ERRORS  EXAMPLES  APPLICATION USAGE  RATIONALE  FUTURE DIRECTIONS  SEE ALSO  COPYRIGHT 

NEXTAFTER(3P) POSIX Programmer's Manual NEXTAFTER(3P)
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.
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl — next representable floatingpoint number
#include <math.h> double nextafter(double x, double y); float nextafterf(float x, float y); long double nextafterl(long double x, long double y); double nexttoward(double x, long double y); float nexttowardf(float x, long double y); long double nexttowardl(long double x, long double y);
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.1‐2008 defers to the ISO C standard. The nextafter(), nextafterf(), and nextafterl() functions shall compute the next representable floatingpoint value following x in the direction of y. Thus, if y is less than x, nextafter() shall return the largest representable floatingpoint number less than x. The nextafter(), nextafterf(), and nextafterl() functions shall return y if x equals y. The nexttoward(), nexttowardf(), and nexttowardl() functions shall be equivalent to the corresponding nextafter() functions, except that the second parameter shall have type long double and the functions shall return y converted to the type of the function if x equals y. An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is nonzero or fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVERFLOW  FE_UNDERFLOW) is nonzero, an error has occurred.
Upon successful completion, these functions shall return the next representable floatingpoint value following x in the direction of y. If x==y, y (of the type x) shall be returned. If 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 x) shall be returned as appropriate for the return type of the function. If x or y is NaN, a NaN shall be returned. If x!=y and the correct function value is subnormal, zero, or underflows, a range error shall occur, and the correct function value (if representable) or 0.0 shall be returned.
These functions shall fail if: Range Error The correct value overflows. If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the overflow floatingpoint exception shall be raised. Range Error The correct value is subnormal or underflows. If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero, then the underflow floatingpoint exception shall be raised. The following sections are informative.
None.
On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be nonzero. When <tgmath.h> is included, note that the return type of nextafter() depends on the generic typing deduced from both arguments, while the return type of nexttoward() depends only on the generic typing of the first argument.
None.
None.
feclearexcept(3p), fetestexcept(3p) The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of Error Conditions for Mathematical Functions, math.h(0p), tgmath.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology  Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.12008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
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/manpages/reporting_bugs.html .
IEEE/The Open Group 2013 NEXTAFTER(3P)