RosettaCodeData/Task/Binary-search/PL-I/binary-search.pli

/* A binary search of list A for element M */
search: procedure (A, M) returns (fixed binary);
   declare (A(*), M) fixed binary;
   declare (l, r, mid) fixed binary;

   l = lbound(a,1)-1; r = hbound(A,1)+1;
   do while (l <= r);
      mid = (l+r)/2;
      if A(mid) = M then return (mid);
      if A(mid) < M then
         L = mid+1;
      else
         R = mid-1;
   end;
   return (lbound(A,1)-1);
end search;