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nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - next representable floating-point number

#include <math.h>

double nextafter(doublex, doubley);

float nextafterf(floatx, floaty);

long double nextafterl(long doublex, long doubley);

double nexttoward(doublex, long doubley);

float nexttowardf(floatx, long doubley);

long double nexttowardl(long doublex, long doubley);

The

nextafter(),nextafterf(), andnextafterl() functions shall compute the next representable floating-point value followingxin the direction ofy. Thus, ifyis less thanx,nextafter() shall return the largest representable floating-point number less thanx. Thenextafter(),nextafterf(), andnextafterl() functions shall returnyifxequalsy.The

nexttoward(),nexttowardf(), andnexttowardl() functions shall be equivalent to the correspondingnextafter() functions, except that the second parameter shall have typelong doubleand the functions shall returnyconverted to the type of the function ifxequalsy.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Upon successful completion, these functions shall return the next representable floating-point value following

xin the direction ofy.If

x==y,y(of the typex) shall be returned.If

xis 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 asx) shall be returned as appropriate for the return type of the function.If

xoryis NaN, a NaN shall be returned.If

x!=yand the correct function value is subnormal, zero, or underflows, a range error shall occur, and either the correct function value (if representable) or 0.0 shall be returned.

These functions shall fail if:

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

Range Error The correct value overflows. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errnoshall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.Range Error The correct value is subnormal or underflows. errnoshall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point 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 non-zero.

None.

None.

feclearexcept() ,fetestexcept() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 .

IEEE/The Open Group |
NEXTAFTER (P) | 2003 |