function search( key : typekey; var r : dataarray ) : integer;
     var high, j, low : integer;

     begin
     low := 1;
     high := n;
     while (r[high].k >= key) and (key > r[low].k) do
          begin
          j := trunc( (key-r[low].k) / (r[high].k-r[low].k) *
                         (high-low) ) + low;
          if      key > r[j].k then low  := j+1
          else if key < r[j].k then high := j-1
                               else low  := j
          end;
     if r[low].k = key then search := low  {*** found(r[low]) ***}
                       else search := -1;  {*** notfound(key) ***}
     end;