state = start
    last-start = input.position
    transition = transition-for (state, input.current-char)
    
    if (transition) {
        state = transition.state                # move
        
        if (state.accepts) {                    # memo
            memo.type = state.type
            memo.position = input.position
        }
        advance (input)                         # advance
    } else {
        push (output-queue, token {             # token
            type = memo.type
            value = input.character-range (
                last-start
                memo.position
            )
        })
        input.position = memo.position + 1      # rewind
        state = start                           # restart
        last-start = input.position
    }