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69 lines
2.8 KiB
Markdown
69 lines
2.8 KiB
Markdown
# salsa
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[](https://travis-ci.org/salsa-rs/salsa)
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[](https://docs.rs/salsa)
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[](https://crates.io/crates/salsa)
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*A generic framework for on-demand, incrementalized computation.*
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## Obligatory warning
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Very much a WORK IN PROGRESS at this point. Ready for experimental use
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but expect frequent breaking changes.
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## Credits
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This system is heavily inspired by [adapton](http://adapton.org/), [glimmer](https://github.com/glimmerjs/glimmer-vm), and rustc's query
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system. So credit goes to Eduard-Mihai Burtescu, Matthew Hammer,
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Yehuda Katz, and Michael Woerister.
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## Key idea
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The key idea of `salsa` is that you define your program as a set of
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**queries**. Every query is used like function `K -> V` that maps from
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some key of type `K` to a value of type `V`. Queries come in two basic
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varieties:
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- **Inputs**: the base inputs to your system. You can change these
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whenever you like.
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- **Functions**: pure functions (no side effects) that transform your
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inputs into other values. The results of queries is memoized to
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avoid recomputing them a lot. When you make changes to the inputs,
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we'll figure out (fairly intelligently) when we can re-use these
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memoized values and when we have to recompute them.
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## How to use Salsa in three easy steps
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Using salsa is as easy as 1, 2, 3...
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1. Define one or more **query groups** that contain the inputs
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and queries you will need. We'll start with one such group, but
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later on you can use more than one to break up your system into
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components (or spread your code across crates).
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2. Define the **query functions** where appropriate.
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3. Define the **database**, which contains the storage for all
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the inputs/queries you will be using. The query struct will contain
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the storage for all of the inputs/queries and may also contain
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anything else that your code needs (e.g., configuration data).
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To see an example of this in action, check out [the `hello_world`
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example](examples/hello_world/main.rs), which has a number of comments
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explaining how things work.
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## Videos about Salsa
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There are also two videos explaining how Salsa works:
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- [How Salsa Works](https://youtu.be/_muY4HjSqVw), which gives a
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high-level introduction to the key concepts involved and shows how
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to use salsa;
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- [Salsa In More Depth](https://www.youtube.com/watch?v=i_IhACacPRY),
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which really digs into the incremental algorithm and explains -- at
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a high-level -- how Salsa is implemented.
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## Getting in touch
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The bulk of the discussion happens in the [issues](https://github.com/salsa-rs/salsa/issues)
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and [pull requests](https://github.com/salsa-rs/salsa/pulls),
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but we have a [zulip chat](https://salsa.zulipchat.com/) as well.
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