43 lines
1.2 KiB
Rust
43 lines
1.2 KiB
Rust
use crate::lenses::{Lens, LensOver, LensView};
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type Getter<T, U> = dyn Fn(T) -> U;
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type Setter<T, U> = dyn Fn(T, U) -> T;
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pub struct FuncLens<T, U>(pub(crate) Box<Getter<T, U>>, pub(crate) Box<Setter<T, U>>);
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impl<T, U> LensView<T> for FuncLens<T, U> {
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type Field = U;
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fn view(&self, thing: T) -> Self::Field {
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(self.0)(thing)
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}
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}
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impl<T: Clone, U> LensOver<T> for FuncLens<T, U> {
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fn over<F>(&self, thing: T, f: F) -> T
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where
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F: FnOnce(Self::Field) -> Self::Field,
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{
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let v = f((self.0)(thing.clone()));
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(self.1)(thing, v)
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}
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fn set(&self, thing: T, v: Self::Field) -> T {
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(self.1)(thing, v)
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}
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}
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/// Makes a lens that implements `LensView<T>` and `LensOver<T>` with the provided functions
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pub fn lens_from_boxed<T, U>(
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getter: Box<Getter<T, U>>,
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setter: Box<Setter<T, U>>,
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) -> Lens<FuncLens<T, U>> {
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Lens(FuncLens(getter, setter))
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}
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/// Makes a lens that implements `LensView<T>` and `LensOver<T>` with the provided functions
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pub fn lens<T, U>(
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getter: impl Fn(T) -> U + 'static,
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setter: impl Fn(T, U) -> T + 'static,
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) -> Lens<FuncLens<T, U>> {
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Lens(FuncLens(Box::new(getter), Box::new(setter)))
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}
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