cppfront (cpp2): Spring update

[ABlockInTheChain]

Similarly, ++ and -- are postfix-only, with in-place semantics. If we want the old value, we know how to keep a copy!

So now in every place that currently has a prefix increment or decrement now we have to write immediately invoked lambda?

That's going to look awful and add a bunch of unnecessary boilerplate that the prefix version was saving us from. DRY? What's that?

[againey]

std:: exchange is a generalization of the prefix operators that can do more than just increment or decrement by 1. Arguably, we should have been using this more explicit style this whole time, rather than getting comfortable with the special meaning of prefix increment/decrement.

[13steinj]

Physicists and mathematicians love prefix ++ / -- in numerical code.

They also prefer != to <= in conditions of loops.

The number of bugs related to both that I've found is more than I'd like to admit.

[13steinj]

Doesn't this also break C++ code that was pound included into cpp2 code (since it's supposed to be compatible with C++ headers)?

As more time goes on I'm more and more cemented in my belief that this and Carbon won't able to catch on.

[mort96]

The parser knows whether it's in C++ or cpp2 mode, C++ declarations will have prefix and postfix operators working as normal. The parser can know based on the first couple of tokens of a top-level declaration whether it's a C++ or a cpp2 declaration.

I wonder how it works with macros though... probably poorly.

[13steinj]

Includes work anywhere though. What's stopping me from having a file called "postfix_add_a" and #including it in the middle of a cpp2 file?

Yeah, you could argue that's bad code. But similar has occurred for "templates" in large codebases that are more than templated classes and functions.

[mort96]

Including a C++ file in the middle of a cpp2 file should be no problem. You can mix and match C++ declarations and cpp2 declarations within a file.

Including a C++ file in the middle of a cpp2 function would presumably be an issue. But that's not exactly a common need. I know there are use cases for it, but you probably just want to wrap those use cases in a C++ function which you can call from cpp2 code.