BSD 4_2 development

[unix-history] / usr / src / new / new / icon / int / operators / random.c

#include "../h/rt.h"
#include "../h/record.h"
#define randval (RSCALE*(k_random=(RANDA*k_random+RANDC)&MAXLONG))

/*
* ?x - produce a randomly selected element of x.
*/

random(nargs, arg1v, arg1, arg0)
int nargs;
struct descrip arg1v, arg1, arg0;
  {
  register int val, i, j;
  register union block *bp;
  long l1;
  double r1;
  char sbuf[MAXSTRING];
  union block *ep;
  struct descrip *dp;
  extern char *alcstr();

  SetBound;
  arg1v = arg1;
  deref(&arg1);

  if (NULLDESC(arg1))
     runerr(113, &arg1);

  if (QUAL(arg1)) {                    /* random char in string */
     if ((val = STRLEN(arg1)) <= 0)
        fail();
     hneed(sizeof(struct b_tvsubs));
     mksubs(&arg1v, &arg1, (int)(randval*val)+1, 1, &arg0);
     ClearBound;
     return;
     }

  switch (TYPE(arg1)) {
     case T_CSET:
        cvstr(&arg1, sbuf);
        if ((val = STRLEN(arg1)) <= 0)
           fail();
        sneed(1);
        STRLEN(arg0) = 1;
        STRLOC(arg0) = alcstr(STRLOC(arg1)+(int)(randval*val), 1);
        ClearBound;
        return;

     case T_REAL:
        r1 = BLKLOC(arg1)->realval;
        if (r1 < 0 || r1 > MAXSHORT)
           runerr(205, &arg1);
        val = (int)r1;
        goto getrand;

     case T_INTEGER:
        val = INTVAL(arg1);
        if (val < 0)
           runerr(205, &arg1);
     getrand:
        if (val == 0)          /* return real in range [0,1) */
           mkreal(randval, &arg0);
        else                   /* return integer in range [1,val] */
           mkint((long)(randval*val) + 1, &arg0);
        ClearBound;
        return;

#ifndef BIT32
     case T_LONGINT:
        runerr(205, &arg1);

#endif
     case T_LIST:
        bp = BLKLOC(arg1);
        val = bp->list.cursize;
        if (val <= 0)
           fail();
        i = (int)(randval*val) + 1;
        j = 1;
        bp = BLKLOC(BLKLOC(arg1)->list.listhead);
        while (i >= j + bp->listb.nused) {
           j += bp->listb.nused;
           if (TYPE(bp->listb.listnext) != T_LISTB)
              syserr("list reference out of bounds in random");
           bp = BLKLOC(bp->listb.listnext);
           }
        i += bp->listb.first - j;
        if (i >= bp->listb.nelem)
           i -= bp->listb.nelem;
        dp = &bp->listb.lelem[i];
        arg0.type = D_VAR + ((int *)dp - (int *)bp);
        BLKLOC(arg0) = dp;
        ClearBound;
        return;

     case T_TABLE:
         bp = BLKLOC(arg1);
         val = bp->table.cursize;
         if (val <= 0)
            fail();
         i = (int)(randval*val) + 1;
         for (j = 0; j < NBUCKETS; j++) {
            for (ep = BLKLOC(bp->table.buckets[j]); ep != NULL;
                 ep = BLKLOC(ep->telem.blink)) {
               if (--i <= 0) {
                  dp = &ep->telem.tval;
                  arg0.type = D_VAR + ((int *)dp - (int *)bp);
                  BLKLOC(arg0) = dp;
                  ClearBound;
                  return;
                  }
               }
            }

     case T_RECORD:
        bp = BLKLOC(arg1);
        val = bp->record.recptr->nfields;
        if (val <= 0)
           fail();
        dp = &bp->record.fields[(int)(randval*val)];
        arg0.type = D_VAR + ((int *)dp - (int *)bp);
        BLKLOC(arg0) = dp;
        ClearBound;
        return;

     default:
        runerr(113, &arg1);
     }
  }
struct b_iproc Brandom = {
  T_PROC,
  sizeof(struct b_proc),
  EntryPoint(random),
  2,
  -1,
  -1,
  0,
  {1, "?"}
  };