2021-11-11 13:50:54 +00:00
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use crate::{
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lenses::{Lens, LensOver, LensView},
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2021-11-11 14:47:55 +00:00
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prisms::Prism,
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2021-11-11 13:50:54 +00:00
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traversals::{Traversal, TraversalOver, TraversalTraverse},
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};
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2021-11-05 13:27:34 +00:00
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2021-11-05 14:22:59 +00:00
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#[derive(Clone, Copy)]
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2021-11-05 13:27:34 +00:00
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pub struct Combination<A, B>(A, B);
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2021-11-11 13:50:54 +00:00
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// additions
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2021-11-11 14:47:55 +00:00
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// lens + lens
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impl<A, B> std::ops::Add<Lens<B>> for Lens<A> {
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type Output = Lens<Combination<Lens<A>, Lens<B>>>;
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2021-11-11 13:29:43 +00:00
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fn add(self, rhs: Lens<B>) -> Self::Output {
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Lens(Combination(self, rhs))
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}
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}
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// traversal + traversal
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impl<A, B> std::ops::Add<Traversal<B>> for Traversal<A> {
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type Output = Traversal<Combination<Traversal<A>, Traversal<B>>>;
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fn add(self, rhs: Traversal<B>) -> Self::Output {
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Traversal(Combination(self, rhs))
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}
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}
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2021-11-11 14:47:55 +00:00
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// traversal + lens
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impl<A, B> std::ops::Add<Lens<B>> for Traversal<A> {
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type Output = Traversal<Combination<Traversal<A>, Traversal<Lens<B>>>>;
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fn add(self, rhs: Lens<B>) -> Self::Output {
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Traversal(Combination(self, rhs.to_traversal()))
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}
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}
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// lens + traversal
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impl<A, B> std::ops::Add<Traversal<B>> for Lens<A> {
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type Output = Traversal<Combination<Traversal<Lens<A>>, Traversal<B>>>;
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fn add(self, rhs: Traversal<B>) -> Self::Output {
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Traversal(Combination(self.to_traversal(), rhs))
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}
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}
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2021-11-11 14:47:55 +00:00
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// traversal + prism
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impl<A, B> std::ops::Add<Prism<B>> for Traversal<A> {
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type Output = Traversal<Combination<Traversal<A>, Traversal<Prism<B>>>>;
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fn add(self, rhs: Prism<B>) -> Self::Output {
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Traversal(Combination(self, rhs.to_traversal()))
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}
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}
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// prism + traversal
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impl<A, B> std::ops::Add<Traversal<B>> for Prism<A> {
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type Output = Traversal<Combination<Traversal<Prism<A>>, Traversal<B>>>;
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fn add(self, rhs: Traversal<B>) -> Self::Output {
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Traversal(Combination(self.to_traversal(), rhs))
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}
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}
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// trait impls for Combination
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impl<A, B, T> LensView<T> for Combination<A, B>
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where
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A: LensView<T>,
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B: LensView<A::Field>,
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{
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type Field = B::Field;
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fn view(&self, thing: T) -> Self::Field {
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B::view(&self.1, A::view(&self.0, thing))
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}
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}
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impl<A, B, T> LensOver<T> for Combination<A, B>
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where
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A: LensOver<T>,
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B: LensOver<A::Field>,
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{
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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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A::over(&self.0, thing, |b| B::over(&self.1, b, f))
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}
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}
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impl<A, B, T> TraversalTraverse<T> for Combination<A, B>
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where
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A: TraversalTraverse<T>,
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B: TraversalTraverse<A::Field>,
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{
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type Field = B::Field;
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fn traverse(&self, thing: T) -> Vec<Self::Field> {
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let a = A::traverse(&self.0, thing);
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a.into_iter()
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.map(|v| B::traverse(&self.1, v))
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.flatten()
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.collect()
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}
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}
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impl<A, B, T> TraversalOver<T> for Combination<A, B>
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where
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A: TraversalOver<T>,
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B: TraversalOver<A::Field>,
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{
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fn over<F>(&self, thing: T, mut f: F) -> T
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where
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F: FnMut(Self::Field) -> Self::Field,
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{
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A::over(&self.0, thing, |b| B::over(&self.1, b, &mut f))
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}
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}
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2021-11-11 14:50:21 +00:00
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#[cfg(test)]
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mod tests {
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use crate::{
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lenses::{_0, _1},
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prisms::_Some,
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traversals::each,
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};
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#[test]
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fn can_view_lens_combination() {
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let a = ((1, 2), 3);
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let lens = _0 + _1;
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let a = lens(a);
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assert_eq!(a, 2);
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}
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#[test]
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fn can_over_lens_combination() {
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let a = ((1, 2), 3);
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let lens = _0 + _1;
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let a = lens(a, |v| v + 1);
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assert_eq!(a, ((1, 3), 3));
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}
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#[test]
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fn can_combine_traversals() {
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let array = [vec![1, 2], vec![3, 4]];
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// combine two traversals
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let res = (each + each)(array, |v| v + 1);
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assert_eq!(res, [vec![2, 3], vec![4, 5]]);
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}
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#[test]
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fn can_combine_traversal_with_lens() {
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let array = [(1, 2), (3, 4), (5, 6)];
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// combine a traversal with a lens
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let t = each + _0;
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// traverse
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let res = t(array);
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assert_eq!(res, vec![1, 3, 5]);
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// over
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let res = t(array, |v| v + 1);
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assert_eq!(res, [(2, 2), (4, 4), (6, 6)]);
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}
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#[test]
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fn can_combine_lens_with_traversal() {
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let array = [(1, 2), (3, 4), (5, 6)];
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// combine a traversal with a lens
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let t = _0 + each;
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// traverse
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let res = t(array);
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assert_eq!(res, vec![1, 2]);
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// over
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let res = t(array, |v| v + 1);
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assert_eq!(res, [(2, 3), (3, 4), (5, 6)]);
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}
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#[test]
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fn can_combine_prism_with_traversal() {
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let array = [Some(1), None, Some(3), None, Some(5)];
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// combine a traversal with a lens
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let t = each + _Some;
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// traverse
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let res = t(array);
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assert_eq!(res, vec![1, 3, 5]);
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// over
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let res = t(array, |v| v + 1);
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assert_eq!(res, [Some(2), None, Some(4), None, Some(6)]);
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}
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#[test]
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fn can_combine_traversal_with_prism() {
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let array = Some([1, 2, 3]);
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// combine a traversal with a lens
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let t = _Some + each;
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// traverse
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let res = t(array);
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assert_eq!(res, vec![1, 2, 3]);
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// over
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let res = t(array, |v| v + 1);
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assert_eq!(res, Some([2, 3, 4]));
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let array: Option<[i32; 3]> = None;
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// traverse
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let res = t(array);
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assert_eq!(res, vec![]);
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// over
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let res = t(array, |v| v + 1);
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assert_eq!(res, None);
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}
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}
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