Solution to Exercise 4.1

[jonathantorres]

function list_of_values_left(exps, env) {
    function loop(exps) {
        if (is_null(exps)) {
            return null;
        }
        return pair(evaluate(head(exps), env), loop(tail(exps)));
    }
    return loop(exps);
}

function list_of_values_right(exps, env) {
    return reverse(list_of_values_left(reverse(exps), env));
}

[EmilyOng]

Sharing an alternative as well :)

// Left-To-Right
function list_of_values(exps, env) {
    return is_null(exps)
        ? null
        : pair(
            evaluate(head(exps), env),
	    list_of_values(tail(exps), env)
        );
}
// Right-To-Left
function list_of_values(exps, env) {
    return is_null(exps)
        ? null
        : append(
            list_of_values(tail(exps), env),
            list(evaluate(head(exps), env))
        );
}

[martin-henz]

None of your solutions are correct. In your solutions, the evaluation order of arguments depends on the evaluation order of arguments of pair and append.

[tch1001]

does this work?

// left to right
function list_of_values_left_to_right(exps, env) {
    return is_null(exps) ? null : (() => {
            const fst = evaluate(head(exps), env);
            const snd = list_of_values_left_to_right(tail(exps),env);
            return pair(fst, snd);
    })();
}
// right to left
function list_of_values_right_to_left(exps, env){
    return is_null(exps) ? null : (() => {
            const snd = list_of_values_right_to_left(tail(exps),env);
            const fst = evaluate(head(exps), env);
            return pair(fst, snd);
    })();
}