Learning that you can use unions in C for grouping things into namespaces

Re:Learning that you can use unions in C for grouping things... by nextaccountic on Monday August 02, 2021 @07:39AM (#28035343)

> BTW, D is the first language of its type (curly brace static compilation) to be able to execute arbitrary code at compile time. It started as kind of "let's see what happens if I implement this", and it spawned an explosion of creativity. It has since been adopted by other languages.

I don't know much about D compile time evaluation. How is it better than macros/templates?

Also, what do you think about Haskell's and Rust's approach of generics with typeclass/trait bounds?

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by d110af5ccf on Monday August 02, 2021 @08:08AM (#28035542)

> D compile time evaluation. How is it better than macros/templates?

CTFE isn't better than templates, it's a completely different tool. CTFE computes a result at compile time as though you had written a literal in the source code. Templates generate blocks of specialized code on the fly based on various parameters (typically types). They solve different problems.

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by nextaccountic on Monday August 02, 2021 @02:03PM (#28040341)

I think that Walter was trying to say that D gets by doing the same things that people use macros for, but without macros. I interpreted this as meaning that D uses CTFE in those same situations. Am I wrong?

What does D do, then?

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by d110af5ccf on Monday August 02, 2021 @09:05PM (#28044633)

I think he was saying that sufficiently powerful languages provide enough features that you won't need macros in the first place. If you feel that you do for some reason, go find a more powerful language instead.

> What does D do, then?

Most mainstream languages, D included, very intentionally don't provide any features that could potentially be used to extend the language itself on the fly. (At least not in a straightforward manner. Obviously the C preprocessor kind of sort of facilitates a bit of this.)

As a counterexample, Rust does provide some of this in the form of procedural macros but doesn't provide (to the best of my knowledge) an equivalent to Lisp reader macros.

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by WalterBright on Monday August 02, 2021 @01:45PM (#28040045)

I wish you luck with it. If you send me an email, when I find what I wrote about it I'll pass it along to you.

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by nextaccountic on Monday August 02, 2021 @02:08PM (#28040415)

I think you replied the wrong comment

[ Parent | on HN ]

Re:Learning that you can use unions in C for grouping things... by WalterBright on Monday August 02, 2021 @07:35PM (#28044060)

Oops, indeed I did. Replied to the right one!

[ Parent | on HN ]