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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 dif-
       fer (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 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 excep-
       tion 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 representation has DBL_MANT_DIG > DBL_MAX_EXP.

       On  error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are indepen-
       dent 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 Mathematical Functions, <math.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)