I have met people who were already earning a paycheck as professional C programmers, who didn't fully grasp what it meant to return a value from a function. If

I have met people who were already earning a paycheck as professional C programmers, who didn't fully grasp what it meant to return a value from a function. If I were teaching beginners these days, I would do what SICP does and tackle the substitution model of evaluation head-on at an early stage.