Comment by sparkie

Don't forget about the `prog*` family.

---

    (prog1 foo bar*)

Evaluates foo, then bar(s), and returns the result of evaluating foo and discards the results of bar(s).

Useful if `foo` is the condition and you need to perform some change to it immediately after, eg:

    (while (prog1 (< next prev) (setq prev next)) ...)

---

    (prog2 foo bar baz*)

Evaluates foo, then bar, then baz(s) (if present), returns the result of evaluating bar and discards the results of evaluating foo and baz(s).

Might be what GP wants. `foo` is the preparation, `bar` is the condition`, and `baz` can be some post-condition mutation on the compared value. Not too dissimilar to

    for (pre, cond, post) {}

With `prog2` you could achieve similar behavior with no built in `for`:

    (while (prog2 pre cond post) ...)

---

    (progn foo*)

Evaluate each foo in order, return the result of evaluating the last element of foo and discard all the others.

`progn` is similar to repeated uses of the comma operator in C, which GP has possibly overlooked as one solution.

    while (prepare, condition) { process }