RFC for const generics #42

xunilrj · 2024-10-27T13:20:03Z

README.md

…ystem

IGI-111

LGTM, the definition itself ends up pretty straightforward, the hard part is going to be the monomorphization implementation.

ironcev · 2025-01-30T12:52:48Z

rfcs/0015-const-generics.md

+
+[motivation]: #motivation
+
+Some types have constants, specifically unsigned integers, as their definition (e.g. arrays and string arrays). Without `const generics` it is impossible to have `impl` items for all instances of these types.


Suggested change

Some types have constants, specifically unsigned integers, as their definition (e.g. arrays and string arrays). Without `const generics` it is impossible to have `impl` items for all instances of these types.

Some types have constants, specifically unsigned integers, as a part of their definition (e.g. arrays and string arrays). Without `const generics` it is impossible to have a single `impl` item for all instances of these types.

ironcev · 2025-01-30T12:59:31Z

rfcs/0015-const-generics.md

+A simple example would be:
+
+```rust
+fn id<const SIZE: usize>(array: [u64; SIZE]) -> [u64; SIZE] {


In most of the code samples usize is used which is misleading because this type does not exist in Sway. Was the intention maybe to emphasize that any unsigned type can be used?

Even in that case, the proposal would be to go with u64 or other concrete types in examples and specify in the RFC which types can be used in const generics.

Or to mention on the top of the Guide-level explanation that usize means any of the types: u8, ...

Still, in this particular example even that is misleading because currently array size must be u64.

Suggested change

fn id<const SIZE: usize>(array: [u64; SIZE]) -> [u64; SIZE] {

fn id<const SIZE: u64>(array: [u64; SIZE]) -> [u64; SIZE] {

ironcev · 2025-01-30T12:59:52Z

rfcs/0015-const-generics.md

+This also allows `impl` items such as
+
+```rust
+impl<const N: usize> AbiEncode for str[N] {


Suggested change

impl<const N: usize> AbiEncode for str[N] {

impl<const N: u64> AbiEncode for str[N] {

ironcev · 2025-01-30T13:00:45Z

rfcs/0015-const-generics.md

+
+[reference-level-explanation]: #reference-level-explanation
+
+This new syntax has three forms: declarations, instantiations and references.


Suggested change

This new syntax has three forms: declarations, instantiations and references.

This new syntax has three forms: declarations, instantiations, and references.

ironcev · 2025-01-30T13:01:13Z

rfcs/0015-const-generics.md

+
+This new syntax has three forms: declarations, instantiations and references.
+
+"const generics declarations" can appear anywhere all other generic arguments declarations are valid:


Suggested change

"const generics declarations" can appear anywhere all other generic arguments declarations are valid:

"Const generics declarations" can appear anywhere all other generic arguments declarations are valid:

ironcev · 2025-01-30T13:39:37Z

rfcs/0015-const-generics.md

+```
+6. Struct/enum support for const generics
+7. Function/method declaration;
+8. `impl` declarations.


Suggested change

8. `impl` declarations.

8. `impl` declarations;

ironcev · 2025-01-30T13:39:48Z

rfcs/0015-const-generics.md

+6. Struct/enum support for const generics
+7. Function/method declaration;
+8. `impl` declarations.
+9. Function/method reference;


Suggested change

9. Function/method reference;

9. Function/method reference.

ironcev · 2025-01-30T13:41:10Z

rfcs/0015-const-generics.md

+
+[prior-art]: #prior-art
+
+This RFC is partially based on Rust's own const generic system: https://doc.rust-lang.org/reference/items/generics.html#const-generics, https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html, https://rust-lang.github.io/rfcs/2000-const-generics.html, https://doc.rust-lang.org/beta/unstable-book/language-features/generic-const-exprs.html


Suggested change

This RFC is partially based on Rust's own const generic system: https://doc.rust-lang.org/reference/items/generics.html#const-generics, https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html, https://rust-lang.github.io/rfcs/2000-const-generics.html, https://doc.rust-lang.org/beta/unstable-book/language-features/generic-const-exprs.html

This RFC is partially based on Rust's own const generic system:

- https://doc.rust-lang.org/reference/items/generics.html#const-generics

- https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html

- https://rust-lang.github.io/rfcs/2000-const-generics.html

- https://doc.rust-lang.org/beta/unstable-book/language-features/generic-const-exprs.html

ironcev · 2025-01-30T13:41:34Z

rfcs/0015-const-generics.md

+
+[unresolved-questions]: #unresolved-questions
+
+1. What is the impact of changing the "method called algorithm"?


Suggested change

1. What is the impact of changing the "method called algorithm"?

1. What is the impact of changing the "method call search algorithm"?

ironcev · 2025-01-30T13:42:09Z

rfcs/0015-const-generics.md

+
+1. What is the impact of changing the "method called algorithm"?
+
+# Future possibilities


As mentioned above, implementing constraints like where N > 0.

IGI-111 reviewed Dec 6, 2024

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RFC for const generics

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xunilrj force-pushed the xunilrj/const-generics branch from 9d50946 to de7209d Compare January 21, 2025 11:40

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xunilrj marked this pull request as ready for review January 21, 2025 11:41

xunilrj mentioned this pull request Jan 24, 2025

Const Generics FuelLabs/sway#6860

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RFC for const generics #42

RFC for const generics #42

xunilrj commented Oct 27, 2024 •

edited by ironcev

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ironcev Jan 30, 2025

ironcev Jan 30, 2025

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ironcev Jan 30, 2025

ironcev Jan 30, 2025

ironcev Jan 30, 2025

ironcev Jan 30, 2025

ironcev Jan 30, 2025


		[motivation]: #motivation

		Some types have constants, specifically unsigned integers, as their definition (e.g. arrays and string arrays). Without `const generics` it is impossible to have `impl` items for all instances of these types.

	fn id<const SIZE: usize>(array: [u64; SIZE]) -> [u64; SIZE] {
	fn id<const SIZE: u64>(array: [u64; SIZE]) -> [u64; SIZE] {

	impl<const N: usize> AbiEncode for str[N] {
	impl<const N: u64> AbiEncode for str[N] {


		[reference-level-explanation]: #reference-level-explanation

		This new syntax has three forms: declarations, instantiations and references.


		This new syntax has three forms: declarations, instantiations and references.

		"const generics declarations" can appear anywhere all other generic arguments declarations are valid:


		[prior-art]: #prior-art

		This RFC is partially based on Rust's own const generic system: https://doc.rust-lang.org/reference/items/generics.html#const-generics, https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html, https://rust-lang.github.io/rfcs/2000-const-generics.html, https://doc.rust-lang.org/beta/unstable-book/language-features/generic-const-exprs.html


		[unresolved-questions]: #unresolved-questions

		1. What is the impact of changing the "method called algorithm"?


		1. What is the impact of changing the "method called algorithm"?

		# Future possibilities

RFC for const generics #42

Are you sure you want to change the base?

RFC for const generics #42

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xunilrj commented Oct 27, 2024 • edited by ironcev Loading

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xunilrj commented Oct 27, 2024 •

edited by ironcev

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