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Can’t you pass “argument” structs as parameters to kinda emulate the feel of named arguments (along with using the Default trait)? I use this in C++ a lot, and

Can’t you pass “argument” structs as parameters to kinda emulate the feel of named arguments (along with using the Default trait)? I use this in C++ a lot, and it seems that some Rust devs are doing this too.

kevincox 4y ago
You can, but it is a mouthful. Especially if you want optional arguments. foo::some_func(foo::SomeFuncArgs{ a: 8, b: Some(false), ..Default::default() }) Personally I would be really happy if `..` could default to `..Default::default()` which would make this a lot cleaner. But even then needing to name a type for the argument struct is noisy. Language-integrated keyword arguments would make this a lot cleaner: foo::some_func( a=8, b=Some(false))
- cercatrova 4y ago
  Indeed, it's basically the same as in JS/TS where you just pass an object of key/values rather than have named arguments.
  - kevincox 4y ago
    Yes, but it is a lot cleaner there because you don't need to specify the name of the type and you don't need to do anything special for optional arguments. I wouldn't mind if it worked this way "under the hood" but syntax sugar for passing that last argument as keyword arguments would be a fantastic quality of life improvement.
- cyber_kinetist 4y ago
  By the way, C++20 designated initializers works like a charm for this. foo::some_func({ .a = 8, .b = false }); (I view this and std::span as the only two usable features in C++20, and pretty much everything else can go to the dustbin or the drawing board.)
- estebank 4y ago
  I'm waiting to getting some spare time to propose (not quite but very close) that in an RFC. A lot of conversation about it from a while back is available at https://internals.rust-lang.org/t/pre-pre-rfc-syntactic-sugar-for-default-default/13234/75 https://internals.rust-lang.org/t/pre-pre-rfc-syntactic-suga...

kevincox 4y ago

You can, but it is a mouthful. Especially if you want optional arguments. foo::some_func(foo::SomeFuncArgs{ a: 8, b: Some(false), ..Default::default() }) Personally I would be really happy if `..` could default to `..Default::default()` which would make this a lot cleaner. But even then needing to name a type for the argument struct is noisy. Language-integrated keyword arguments would make this a lot cleaner: foo::some_func( a=8, b=Some(false))

cercatrova 4y ago
Indeed, it's basically the same as in JS/TS where you just pass an object of key/values rather than have named arguments.
- kevincox 4y ago
  Yes, but it is a lot cleaner there because you don't need to specify the name of the type and you don't need to do anything special for optional arguments. I wouldn't mind if it worked this way "under the hood" but syntax sugar for passing that last argument as keyword arguments would be a fantastic quality of life improvement.
cyber_kinetist 4y ago
By the way, C++20 designated initializers works like a charm for this. foo::some_func({ .a = 8, .b = false }); (I view this and std::span as the only two usable features in C++20, and pretty much everything else can go to the dustbin or the drawing board.)
estebank 4y ago
I'm waiting to getting some spare time to propose (not quite but very close) that in an RFC. A lot of conversation about it from a while back is available at https://internals.rust-lang.org/t/pre-pre-rfc-syntactic-sugar-for-default-default/13234/75 https://internals.rust-lang.org/t/pre-pre-rfc-syntactic-suga...