eval-when-compile permits compile-time definitions that can be used from macros

[khinsen]

Fixes #186

[paultag]

Clever. Very clever. You mentioned this has a precedent, @khinsen? Mind linking me to the docs for some of it (actually just interested, I'll likely merge this after a quick @jd / @olasd signoff that we're not doing something that breaks internals)

[olasd]

Looks good to me from an internals POV. The hy_eval dance could be factored out in a common function.

From a semantics POV, the eval-when-compiled thing is evaluated at runtime too. Is that intended? (I feel it contradicts the meaning of the eval-when-compile special form in elisp, for instance). Either way, it should be tested.

[khinsen]

I actually stole both the name and the semantics from elisp. I agree that the name suggests that the evaluation is limited to compile time.

I don't see a point in evaluating something only at compile time but not at runtime, so I'd like to keep the semantics of the current version, but I am open to suggestions for a clearer name.

[olasd]

http://www.gnu.org/software/emacs/manual/html_node/elisp/Eval-During-Compile.html suggests the opposite. The semantics you are talking about seem to be from eval-and-compile? I think we need some @jd knowledge here :)

[khinsen]

Oops, you are right, it's eval-and-compile that I tried to imitate. And now I am hesitation about whay I want, because in elisp it's eval-when-compile that is used much more frequently.

Looking at my own use cases, all I need is eval-when-compile but it never does any harm to use eval-and-compile instead. I can easily construct use cases that require one or the other, but they are made up. My real-life Lisp experience is mostly Clojure, which doesn't have the distinction between compile and load/eval time.

[paultag]

This seems like thrilling stuff; can I get a @jd comment on this?

[paultag]

Throw caution to the wind! Thanks, @khinsen !