Re: Understanding macroexp.el

[Stefan Monnier]

>> For byte-compiled code there should be no difference between the two
>> expansions.
> What's the use of `macroexp-unprogn' then at all?

It's when you care to generate slightly cleaner code it's easy to do so.
It usually doesn't really matter much.

> Or does it make a difference in other cases?

I can't remember exactly what motivated me to introduce
macroexp-unprogn, but I don't think it was a strong need.
I can retroactively come up with scenarios where it could make
a difference, but they all seem reasonably infrequent.
E.g. (+ 1 2) will be optimized to 3, but (+ 1 (progn 2)) won't.


        Stefan