“State” means the current state of the program. What elms lacks is mutation of that state - you never change it, but only have a function taking the old state,

“State” means the current state of the program. What elms lacks is mutation of that state - you never change it, but only have a function taking the old state, and returning the new state. Thus every change is atomic, and you can record each change and in the debugger travel back and forth in time. Maybe calling immutable programming “stateless” is a misnomer, but “immutable state” would be better.