2.9BSD - /usr/src/lib/ape/square.c

   1: #include "lint.h"
   2: #ifndef lint
   3: static char sccs_id[] = "%W%	%G%";
   4: #endif lint
   5: #include <stdio.h>
   6: #include <ape.h>
   7: square(a,b) /* b = a^2, recursive version */
   8: PMINT a,b;
   9: {
  10:     MINT low, high, x, y;
  11:     int half;
  12: 
  13:     if (a->len == 0) {  /* first base case -- a==0 */
  14:         xfree(b);
  15:         return;
  16:         }
  17:     half = a->len / 2;
  18:     if (half == 0) {    /* second base case -- a->len == 1 */
  19:         long answer;
  20: 
  21:         answer = ( (long) a->val[0] ) * ( (long) a->val[0] );
  22:         makemint(b,answer);
  23:         return;
  24:         }
  25:     if (half < 0) half = -half;
  26:     low.len = half;
  27:     low.val = a->val;
  28:     high.len = a->len - half;
  29:     high.val = &(a->val[half]);
  30:     x.len = 0;
  31:     y.len = 0;
  32: 
  33:     square(&low,&x);    /* (low+high)^2=low^2+high^2+2low*high */
  34:     square(&high,&y);
  35:     lshift(&y,half+half);
  36:     madd(&x,&y,&x);
  37:     mult(&low,&high,&y);
  38:     lshift(&y,half);
  39:     madd(&x,&y,&x);
  40:     madd(&x,&y,&x);
  41:     xfree(&y);
  42:     *b = x;
  43: }

Defined functions

Defined variables