Time the loops plus an iteration counter. Together they work well. If something is taking long AND is looping a lot then there's a good chance we're running up

Time the loops plus an iteration counter. Together they work well. If something is taking long AND is looping a lot then there's a good chance we're running up against an infinite loop. Additionally we setTimeout and reset the counter so that we don't stop infinite generators. Good point re undecidability, it's a knowledge curse mistake.