61 lines
1.8 KiB
Markdown
61 lines
1.8 KiB
Markdown
# bad optics
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ergonomic lenses in rust
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`bad-optics` implements the haskell concept of lenses, prisms, and traversals in rust
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it does *not* implement the operators, as it's not really a thing we can do in rust
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you will need nightly for this library to work, as it uses a bunch of unstable features. they're technically not *critical*, but i think not having them reduces the ergonomics too much
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does bringing lenses into rust actually make sense? probably not, but it was fun to implement so who can say
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## example
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```rust
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use bad_optics::{
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lenses::{over, set},
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prelude::*,
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};
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fn main() {
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let a = ((1, 2), 3);
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// use view to access inside the tuple
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let res = view(_0, a);
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assert_eq!(res, (1, 2));
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let res = view(_1, a);
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assert_eq!(res, 3);
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// you can combine lenses
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let lens = _0 + _1;
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// use the view function to access
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let res = view(lens, a);
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assert_eq!(res, 2);
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// you can also call the lens as a function
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let res = lens(a);
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assert_eq!(res, 2);
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// call the over function to modify the value
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let a = over(lens, a, |v| v + 1);
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assert_eq!(a, ((1, 3), 3));
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// call the set function to set the value
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let a = set(lens, a, 5);
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assert_eq!(a, ((1, 5), 3));
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// you can also call the lens as a function to modify the value
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let res = lens(a, |v| v + 1);
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assert_eq!(res, ((1, 6), 3));
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}
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```
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## how to use
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bad-optics provides some of the lenses, prisms, and traversals defined in `lens`. i'm still trying to add more, so if there's one you need and it's missing from here, feel free to open a PR
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if you don't know how lenses work, this is not really gonna be a tutorial, you should read [this](https://hackage.haskell.org/package/lens-tutorial-1.0.3/docs/Control-Lens-Tutorial.html) first instead. the general idea is that they are first-class getters and setters
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