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A generic framework for on-demand, incrementalized computation. Inspired by adapton, glimmer, and rustc's query system.
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bors[bot] d4a94fbf07
Merge #440 
440: Change the constructor of `salsa::Id` to const fn r=XFFXFF a=Y-Nak

This change is motivated to allow interned structs to have default const instances and prefill them in db initialization.

A specific example is managing symbols as a salsa interned struct in a compiler implementation. By declaring keywords as `const` symbols, we can handle keywords without going through their internal representation as rustc does (ref: [rustc_span::symbol](https://github.com/rust-lang/rust/blob/master/compiler/rustc_span/src/symbol.rs)). 
Conceptually, it'd look like the one below.

```rust
#[salsa::interned]
pub struct Symbol {
    data: String,
}

const SELF_SYM: Symbol = Symbol(salsa::Id::from_u32(1))
...

/// This function is called in db initialization.
fn prefill(db: &dyn HirDb) {
       Symbol::new(db, "self".to_string());
       ...
}
```

Co-authored-by: Yoshitomo Nakanishi <yurayura.rounin.3@gmail.com>
2023-04-24 08:45:47 +00:00
.github/workflows Run CI on trybuild test updates 2023-03-21 11:55:20 -04:00
book Update videos.md with architecture walkthrough 2023-02-03 17:45:17 +07:00
components Change the constructor of salsa::Id to const fn 2023-04-12 13:36:17 +02:00
examples Remove ': salsa::Database' bound from two examples 2021-12-30 11:02:30 +00:00
examples-2022 Update on-demand input docs 2022-09-16 00:14:54 +01:00
salsa-2022-tests Fix trybuild ui test to adapt the change of rustc error message 2023-04-22 11:16:51 +02:00
src Merge #381 2022-08-25 10:34:44 +00:00
tests Fix clippy issues 2022-08-24 18:45:53 +02:00
.dir-locals.el ask emacs to rustfmt on save 2018-09-28 11:26:57 -04:00
.gitignore Fix clippy issues 2022-08-24 18:45:53 +02:00
bors.toml Update book workflow 2021-09-28 22:03:05 +02:00
Cargo.toml Move calc and lazy-input examples to examples-2022 2022-09-16 00:14:44 +01:00
FAQ.md Update New Mexico state question 2020-06-26 15:48:29 +01:00
LICENSE-APACHE add readme, license, etc 2018-09-28 11:01:27 -04:00
LICENSE-MIT add readme, license, etc 2018-09-28 11:01:27 -04:00
README.md Fix Chinese book link 2022-09-24 01:00:36 +09:00
RELEASES.md highlight breaking changes 2019-08-15 08:08:00 -04:00
rustfmt.toml add empty/default rustfmt.toml 2022-08-22 19:19:22 +08:00

README.md

salsa

Test Book Released API docs Crates.io

A generic framework for on-demand, incrementalized computation.

Salsa Logo

Obligatory warning

Very much a WORK IN PROGRESS at this point. Ready for experimental use but expect frequent breaking changes.

Credits

This system is heavily inspired by adapton, glimmer, and rustc's query system. So credit goes to Eduard-Mihai Burtescu, Matthew Hammer, Yehuda Katz, and Michael Woerister.

Key idea

The key idea of salsa is that you define your program as a set of queries. Every query is used like function K -> V that maps from some key of type K to a value of type V. Queries come in two basic varieties:

  • Inputs: the base inputs to your system. You can change these whenever you like.
  • Functions: pure functions (no side effects) that transform your inputs into other values. The results of queries are memoized to avoid recomputing them a lot. When you make changes to the inputs, we'll figure out (fairly intelligently) when we can re-use these memoized values and when we have to recompute them.

Want to learn more?

To learn more about Salsa, try one of the following:

Getting in touch

The bulk of the discussion happens in the issues and pull requests, but we have a zulip chat as well.