7 releases (breaking)

new 0.22.0 May 23, 2025
0.21.1 May 1, 2025
0.21.0 Apr 29, 2025
0.20.0 Apr 22, 2025
0.1.0 Feb 19, 2025

#536 in Rust patterns

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27,934 downloads per month
Used in 24 crates (via salsa)

Apache-2.0 OR MIT

67KB
1K SLoC

This crate defines various macro_rules macros used as part of Salsa's internal plumbing. These macros are re-exported under salsa::plumbing``. The procedural macros emit calls to these macro_rules` macros after doing error checking.

Using macro_rules macro definitions is generally more ergonomic and also permits true hygiene for local variables (sadly not items).

Currently the only way to have a macro that is re-exported from a submodule is to use multiple crates, hence the existence of this crate.


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.

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.

Contributing

To create a release and publish to crates.io, update the version field in Cargo.toml. After pushed, GitHub Actions will publish the crates to crates.io automatically.

No runtime deps