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47 lines
1.8 KiB
Markdown
47 lines
1.8 KiB
Markdown
# 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, glimmer, 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
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of **queries**. Queries come in two basic 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 **database traits** that contain the inputs
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and queries you will need. We'll start with one such trait, 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. **Implement the query functions** where appropriate.
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3. Define the **database struct**, 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. The [`hello_world`
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README](examples/hello_world/README.md) has a more detailed writeup.
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