1FLOOR(3P)                  POSIX Programmer's Manual                 FLOOR(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       floor, floorf, floorl - floor function
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SYNOPSIS

15       #include <math.h>
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17       double floor(double x);
18       float floorf(float x);
19       long double floorl(long double x);
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21

DESCRIPTION

23       These functions shall compute the largest integral  value  not  greater
24       than x.
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26       An  application  wishing to check for error situations should set errno
27       to zero and  call  feclearexcept(FE_ALL_EXCEPT)  before  calling  these
28       functions.   On return, if errno is non-zero or fetestexcept(FE_INVALID
29       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has
30       occurred.
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RETURN VALUE

33       Upon  successful  completion,  these functions shall return the largest
34       integral value not greater than x, expressed as  a  double,  float,  or
35       long double, as appropriate for the return type of the function.
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37       If x is NaN, a NaN shall be returned.
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39       If x is ±0 or ±Inf, x shall be returned.
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41       If  the  correct  value would cause overflow, a range error shall occur
42       and floor(), floorf(), and floorl() shall return the value of the macro
43       -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.
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ERRORS

46       These functions shall fail if:
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48       Range Error
49              The result would cause an overflow.
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51       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
52       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
53       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow
54       floating-point exception shall be raised.
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57       The following sections are informative.
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EXAMPLES

60       None.
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APPLICATION USAGE

63       The integral value returned by these functions might not be expressible
64       as  an  int or long. The return value should be tested before assigning
65       it to an integer type to avoid the  undefined  results  of  an  integer
66       overflow.
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68       The  floor()  function can only overflow when the floating-point repre‐
69       sentation has DBL_MANT_DIG > DBL_MAX_EXP.
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71       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
72       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
73       at least one of them must be non-zero.
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RATIONALE

76       None.
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FUTURE DIRECTIONS

79       None.
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SEE ALSO

82       ceil(), feclearexcept(), fetestexcept(), isnan(), the Base  Definitions
83       volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi‐
84       tions for Mathematical Functions, <math.h>
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87       Portions of this text are reprinted and reproduced in  electronic  form
88       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
89       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
90       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
91       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
92       event of any discrepancy between this version and the original IEEE and
93       The Open Group Standard, the original IEEE and The Open Group  Standard
94       is  the  referee document. The original Standard can be obtained online
95       at http://www.opengroup.org/unix/online.html .
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99IEEE/The Open Group                  2003                            FLOOR(3P)
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