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2 points by akkartik 246 days ago | link | parent

Thanks for that example. I see now that you mostly only need to worry about multiple evaluation for the `%test` branch; `%then` and `%else` should be exclusive anyway, and I'm not concerned about the growth in macroexpanded code when duplicating a few s-expressions.

You could still have repeated use within a '%then' or '%else' block:

    (aif (test)
      (something)
      (do %then %then))
But it should suffice to perform one evaluation in each branch. Cool! That seems simpler than some of the alternatives I'd been thinking about. I'd try to evaluate everything ahead of time and then realize that I shouldn't run `%else` if the `%test` returns a truthy value.


2 points by adas 246 days ago | link

Didn't consider a double `%then` or `%else`, thanks. Raises some interesting problems.

Generally the plan is to have a special character control whether it gets bound or inlined, probably `!`. So say `%test!` would get inlined like right now, while using `%test` would bind (and doing both would also be possible). But for a `%then` you'd generally only want to bind if there's 2+ so I could count usages instead.

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