1NEXTAFTER(3P)              POSIX Programmer's Manual             NEXTAFTER(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

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

16       #include <math.h>
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18       double nextafter(double x, double y);
19       float nextafterf(float x, float y);
20       long double nextafterl(long double x, long double y);
21       double nexttoward(double x, long double y);
22       float nexttowardf(float x, long double y);
23       long double nexttowardl(long double x, long double y);
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DESCRIPTION

27       The nextafter(), nextafterf(), and nextafterl() functions shall compute
28       the next representable floating-point value following x in  the  direc‐
29       tion  of  y.   Thus,  if y is less than x, nextafter() shall return the
30       largest  representable  floating-point  number   less   than   x.   The
31       nextafter(), nextafterf(), and nextafterl() functions shall return y if
32       x equals y.
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34       The nexttoward(), nexttowardf(), and nexttowardl() functions  shall  be
35       equivalent  to the corresponding nextafter() functions, except that the
36       second parameter shall have type long double and  the  functions  shall
37       return y converted to the type of the function if x equals y.
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39       An  application  wishing to check for error situations should set errno
40       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these
41       functions.   On return, if errno is non-zero or fetestexcept(FE_INVALID
42       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has
43       occurred.
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RETURN VALUE

46       Upon  successful completion, these functions shall return the next rep‐
47       resentable floating-point value following x in the direction of y.
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49       If x== y, y (of the type x) shall be returned.
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51       If x is finite and the correct function value would overflow,  a  range
52       error  shall  occur and ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (with the
53       same sign as x) shall be returned as appropriate for the return type of
54       the function.
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56       If x or y is NaN, a NaN shall be returned.
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58       If  x!=  y and the correct function value is subnormal, zero, or under‐
59       flows, a range error shall occur, and either the correct function value
60       (if representable) or 0.0 shall be returned.
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ERRORS

63       These functions shall fail if:
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65       Range Error
66              The correct value overflows.
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68       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
69       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
70       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow
71       floating-point exception shall be raised.
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73       Range Error
74              The correct value is subnormal or underflows.
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76       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
77       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
78       (math_errhandling & MATH_ERREXCEPT) is  non-zero,  then  the  underflow
79       floating-point exception shall be raised.
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82       The following sections are informative.
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EXAMPLES

85       None.
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APPLICATION USAGE

88       On   error,   the   expressions  (math_errhandling  &  MATH_ERRNO)  and
89       (math_errhandling & MATH_ERREXCEPT) are independent of each other,  but
90       at least one of them must be non-zero.
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RATIONALE

93       None.
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FUTURE DIRECTIONS

96       None.
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SEE ALSO

99       feclearexcept(),   fetestexcept(),   the  Base  Definitions  volume  of
100       IEEE Std 1003.1-2001, Section 4.18, Treatment of Error  Conditions  for
101       Mathematical Functions, <math.h>
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104       Portions  of  this text are reprinted and reproduced in electronic form
105       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
106       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
107       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
108       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
109       event of any discrepancy between this version and the original IEEE and
110       The  Open Group Standard, the original IEEE and The Open Group Standard
111       is the referee document. The original Standard can be  obtained  online
112       at http://www.opengroup.org/unix/online.html .
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116IEEE/The Open Group                  2003                        NEXTAFTER(3P)
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