procedure main(arglist)

   s := "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"

   write(" s=",image(s))
   write("s1=",image(s1 := rle_encode(s)))
   write("s2=",image(s2 := rle_decode(s1)))

   if s ~== s2 then write("Encode/Decode problem.")
               else write("Encode/Decode worked.")
end

procedure rle_encode(s)
   es := ""
   s ? while c := move(1) do es ||:= *(move(-1),tab(many(c))) || c
   return es
end

procedure rle_decode(es)
   s := ""
   es ? while s ||:= Repl(tab(many(&digits)),move(1))
   return s
end

procedure Repl(n, c)
    return repl(c,n)
end