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FLOOR(3P)                  POSIX Programmer's Manual                 FLOOR(3P)

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.
NAME
       floor, floorf, floorl - floor function
SYNOPSIS
       #include <math.h>
       double floor(double x);
       float floorf(float x);
       long double floorl(long double x);

DESCRIPTION
       These functions shall compute the largest integral  value  not  greater
       than x.
       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 non-zero or fetestexcept(FE_INVALID
       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error  has
       occurred.
RETURN VALUE
       Upon  successful  completion,  these functions shall return the largest
       integral value not greater than x, expressed as  a  double,  float,  or
       long double, as appropriate for the return type of the function.
       If x is NaN, a NaN shall be returned.
       If x is +-0 or +-Inf, x shall be returned.
       If  the  correct  value would cause overflow, a range error shall occur
       and floor(), floorf(), and floorl() shall return the value of the macro
       -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.
ERRORS
       These functions shall fail if:
       Range Error
              The result would cause an overflow.
       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then the overflow
       floating-point exception shall be raised.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       The integral value returned by these functions might not be expressible
       as  an  int or long. The return value should be tested before assigning
       it to an integer type to avoid the  undefined  results  of  an  integer
       overflow.
       The  floor()  function can only overflow when the floating-point repre-
       sentation has DBL_MANT_DIG > DBL_MAX_EXP.
       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.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       ceil(), feclearexcept(), fetestexcept(), isnan(), the Base  Definitions
       volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi-
       tions for Mathematical Functions, <math.h>
COPYRIGHT
       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                  2003                            FLOOR(3P)