// Testing more interesting state types contract Stack = type stack('a) = list('a) record state = { stack : stack(string), size : int } function init(ss : list(string)) = { stack = ss, size = length(ss) } private function length(xs) = switch(xs) [] => 0 _ :: xs => length(xs) + 1 stateful function pop() : string = switch(state.stack) s :: ss => put(state{ stack = ss, size = state.size - 1 }) s stateful function push(s) = put(state{ stack = s :: state.stack, size = state.size + 1 }) state.size function all() = state.stack function size() = state.size