Phelype Oleinik

> I am writing a package and would like to use `pgf`'s maths engine for some computations. Going off on a bit of a tangent, but why don't you use...

Well, maybe it shouldn't be supported, but it's convenient. And it doesn't need checking much, just these two changes: ```latex \ExplSyntaxOn \cs_gset:Npn \__bool_if_p:n #1 { \tl_if_empty:oT { \use_none:nn #1 ....

I ruled it as “should be fixed” mostly because it worked before, so to avoid breakage. Though given it remain undetected for a good amount of time, maybe it's not...

This is true for everything described in `interface3` that takes `` as argument (notably `\..._map_inline:` functions). If I recall correctly, somewhere in `interface3` it is mentioned that inside a definition...

> I notice another option: tell users to use the already currently working \input filename The primitive is used, but it's not expandable because of `\@ifnextchar`, which solves the problems...

> one option you didn't mention is (on platforms where you have added the primitive `\input{..}` just provide a no @ version of `\@@input` and let the engine handle the...

> I'm not sure how you mean. Without an assignment, all we can do is grab an argument up-to left brace and see if that's empty. That's explicitly _not_ in...

@davidcarlisle Yeah, maybe generic `file/before` and `file/after` could be left out. The advantage of the key-val syntax is that you can do `\input[with-hooks]` or whatever if you need hooks or...

There are argument types `G`, `g`, `l`, and `u`, but they are deprecated, thus documented in a separate (and intentionally harder to find) section: https://github.com/latex3/latex3/blob/25523bf1497a3fb3f8868bb1ce8861f6b9e0fae6/l3packages/xparse/xparse.dtx#L465-L490 Not sure what these two...

Not even mention, I'd say.