floor(P)                                               floor(P)





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
       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  IEEE Std 1003.1-2001
       defers to the ISO C standard.

       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  feclearex-
       cept(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  float-
       ing-point representation 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 Conditions for Mathe-
       matical 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  Operat-
       ing System Interface (POSIX), The Open Group Base Speci-
       fications Issue 6, Copyright (C) 2001-2003 by the Insti-
       tute  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.open-
       group.org/unix/online.html .



POSIX                         2003                     floor(P)
