first shot at TAHOE.

[unix-history] / usr / src / lib / libm / common_source / floor.c

/*      @(#)floor.c     4.2     9/11/85; 1.3 (ucb.elefunt) %G% */

/*
* floor and ceil-- greatest integer <= arg
* (resp least >=)
*/

double  modf();

double
floor(d)
double d;
{
       double fract;

       if (d<0.0) {
               d = -d;
               fract = modf(d, &d);
               if (fract != 0.0)
                       d += 1;
               d = -d;
       } else
               modf(d, &d);
       return(d);
}

double
ceil(d)
double d;
{
       return(-floor(-d));
}

/*
* algorithm for rint(x) in pseudo-pascal form ...
*
* real rint(x): real x;
*      ... delivers integer nearest x in direction of prevailing rounding
*      ... mode
* const        L = (last consecutive integer)/2
*        = 2**55; for VAX D
*        = 2**52; for IEEE 754 Double
* real s,t;
* begin
*      if x != x then return x;                ... NaN
*      if |x| >= L then return x;              ... already an integer
*      s := copysign(L,x);
*      t := x + s;                             ... = (x+s) rounded to integer
*      return t - s
* end;
*
* Note: Inexact will be signaled if x is not an integer, as is
*      customary for IEEE 754.  No other signal can be emitted.
*/
#if (defined(VAX)||defined(TAHOE))
static long Lx[] = {0x5c00,0x0};                /* 2**55 */
#define L *(double *) Lx
#else   /* IEEE double */
static double L = 4503599627370496.0E0;         /* 2**52 */
#endif
double
rint(x)
double x;
{
       double s,t,one = 1.0,copysign();
#if (!defined(VAX)&&!defined(TAHOE))
       if (x != x)                             /* NaN */
               return (x);
#endif
       if (copysign(x,one) >= L)               /* already an integer */
           return (x);
       s = copysign(L,x);
       t = x + s;                              /* x+s rounded to integer */
       return (t - s);
}