I've often thought about an editor for a stack/concatenative language that makes the arity of words clearer. like when you select a word it highlights which of

I've often thought about an editor for a stack/concatenative language that makes the arity of words clearer. like when you select a word it highlights which of the previous words in the definition it's consuming. I don't know if it would work for forth - too low level - but for something like Factor I could see it being really useful.