They are only nested given the common assumption (among programmers, at least) that recursion a stack-like model. From the young child's perspective this is pro

They are only nested given the common assumption (among programmers, at least) that recursion a stack-like model. From the young child's perspective this is probably tail-recursive operation: def up(): if not at top stair: up() Think of recursion in terms of induction. No nested state required.