fix prisms

src/combinations.rs

@@ -1,5 +1,6 @@
 use crate::{
     lenses::{Lens, LensOver, LensView},
+    prisms::Prism,
     traversals::{Traversal, TraversalOver, TraversalTraverse},
 };
 
@@ -8,6 +9,7 @@ pub struct Combination<A, B>(A, B);
 
 // additions
 
+// lens + lens
 impl<A, B> std::ops::Add<Lens<B>> for Lens<A> {
     type Output = Lens<Combination<Lens<A>, Lens<B>>>;
 
@@ -15,6 +17,7 @@ impl<A, B> std::ops::Add<Lens<B>> for Lens<A> {
         Lens(Combination(self, rhs))
     }
 }
+// traversal + traversal
 impl<A, B> std::ops::Add<Traversal<B>> for Traversal<A> {
     type Output = Traversal<Combination<Traversal<A>, Traversal<B>>>;
 
@@ -22,6 +25,7 @@ impl<A, B> std::ops::Add<Traversal<B>> for Traversal<A> {
         Traversal(Combination(self, rhs))
     }
 }
+// traversal + lens
 impl<A, B> std::ops::Add<Lens<B>> for Traversal<A> {
     type Output = Traversal<Combination<Traversal<A>, Traversal<Lens<B>>>>;
 
@@ -29,6 +33,7 @@ impl<A, B> std::ops::Add<Lens<B>> for Traversal<A> {
         Traversal(Combination(self, rhs.to_traversal()))
     }
 }
+// lens + traversal
 impl<A, B> std::ops::Add<Traversal<B>> for Lens<A> {
     type Output = Traversal<Combination<Traversal<Lens<A>>, Traversal<B>>>;
 
@@ -36,6 +41,22 @@ impl<A, B> std::ops::Add<Traversal<B>> for Lens<A> {
         Traversal(Combination(self.to_traversal(), rhs))
     }
 }
+// traversal + prism
+impl<A, B> std::ops::Add<Prism<B>> for Traversal<A> {
+    type Output = Traversal<Combination<Traversal<A>, Traversal<Prism<B>>>>;
+
+    fn add(self, rhs: Prism<B>) -> Self::Output {
+        Traversal(Combination(self, rhs.to_traversal()))
+    }
+}
+// prism + traversal
+impl<A, B> std::ops::Add<Traversal<B>> for Prism<A> {
+    type Output = Traversal<Combination<Traversal<Prism<A>>, Traversal<B>>>;
+
+    fn add(self, rhs: Traversal<B>) -> Self::Output {
+        Traversal(Combination(self.to_traversal(), rhs))
+    }
+}
 
 // trait impls for Combination
 

src/fns.rs

@@ -1,5 +1,6 @@
 use crate::{
     lenses::{Lens, LensOver, LensView},
+    prisms::{Prism, PrismPreview},
     traversals::{Traversal, TraversalOver, TraversalTraverse},
 };
 
@@ -120,3 +121,65 @@ where
         L::over(&self.0, args.0, args.1)
     }
 }
+
+// prism preview
+impl<L, A> std::ops::FnOnce<(A,)> for Prism<L>
+where
+    L: PrismPreview<A>,
+{
+    type Output = Option<L::Field>;
+
+    extern "rust-call" fn call_once(self, args: (A,)) -> Self::Output {
+        L::preview(&self.0, args.0)
+    }
+}
+impl<L, A> std::ops::FnMut<(A,)> for Prism<L>
+where
+    L: PrismPreview<A>,
+{
+    extern "rust-call" fn call_mut(&mut self, args: (A,)) -> Self::Output {
+        L::preview(&self.0, args.0)
+    }
+}
+impl<L, A> std::ops::Fn<(A,)> for Prism<L>
+where
+    L: PrismPreview<A>,
+{
+    extern "rust-call" fn call(&self, args: (A,)) -> Self::Output {
+        L::preview(&self.0, args.0)
+    }
+}
+
+// prism over
+impl<L, A, F> std::ops::FnOnce<(A, F)> for Prism<L>
+where
+    A: Clone,
+    L: PrismPreview<A>,
+    F: FnMut(L::Field) -> L::Field,
+{
+    type Output = A;
+
+    extern "rust-call" fn call_once(self, args: (A, F)) -> Self::Output {
+        L::over(&self.0, args.0, args.1)
+    }
+}
+impl<L, A, F> std::ops::FnMut<(A, F)> for Prism<L>
+where
+    A: Clone,
+    L: PrismPreview<A>,
+    F: FnMut(L::Field) -> L::Field,
+{
+    extern "rust-call" fn call_mut(&mut self, args: (A, F)) -> Self::Output {
+        L::over(&self.0, args.0, args.1)
+    }
+}
+impl<L, A, F> std::ops::Fn<(A, F)> for Prism<L>
+where
+    A: Clone,
+    L: PrismPreview<A>,
+    F: FnMut(L::Field) -> L::Field,
+{
+    extern "rust-call" fn call(&self, args: (A, F)) -> Self::Output {
+        L::over(&self.0, args.0, args.1)
+    }
+}

src/prisms/mod.rs

@@ -12,10 +12,28 @@ pub struct Prism<P>(pub(crate) P);
 pub trait PrismPreview<T> {
     type Field;
 
-    fn preview(thing: T) -> Option<Self::Field>;
-}
-pub trait PrismReview<T>: PrismPreview<T> {
-    fn review(thing: Self::Field) -> T;
+    fn preview(&self, thing: T) -> Option<Self::Field>;
+    fn review(&self, thing: Self::Field) -> T;
+    // TODO id like for this to not need clone
+    fn over<F>(&self, thing: T, f: F) -> T
+    where
+        F: FnOnce(Self::Field) -> Self::Field,
+        T: Clone,
+    {
+        if let Some(a) = Self::preview(&self, thing.clone()) {
+            Self::review(&self, f(a))
+        } else {
+            thing
+        }
+    }
+
+    fn set(&self, thing: T, v: Self::Field) -> T
+    where
+        T: Clone,
+        Self::Field: Clone,
+    {
+        Self::over(self, thing, move |_| v.clone())
+    }
 }
 
 impl<P, T> PrismPreview<T> for Prism<P>
@@ -24,25 +42,27 @@ where
 {
     type Field = P::Field;
 
-    fn preview(thing: T) -> Option<Self::Field> {
-        P::preview(thing)
+    fn preview(&self, thing: T) -> Option<Self::Field> {
+        P::preview(&self.0, thing)
+    }
+
+    fn review(&self, thing: Self::Field) -> T {
+        P::review(&self.0, thing)
     }
 }
 
-impl<P, T> PrismReview<T> for Prism<P>
-where
-    P: PrismReview<T>,
-{
-    fn review(thing: Self::Field) -> T {
-        P::review(thing)
-    }
+pub fn preview<T, P: PrismPreview<T>>(prism: P, thing: T) -> Option<P::Field> {
+    P::preview(&prism, thing)
 }
-
-pub fn preview<T, P: PrismPreview<T>>(_prism: P, thing: T) -> Option<P::Field> {
-    P::preview(thing)
+pub fn review<T, P: PrismPreview<T>>(prism: P, thing: P::Field) -> T {
+    P::review(&prism, thing)
 }
-pub fn review<T, P: PrismReview<T>>(_prism: P, thing: P::Field) -> T {
-    P::review(thing)
+pub fn over<T: Clone, P: PrismPreview<T>>(
+    prism: P,
+    thing: T,
+    f: impl FnOnce(P::Field) -> P::Field,
+) -> T {
+    P::over(&prism, thing, f)
 }
 
 #[cfg(test)]
@@ -52,13 +72,13 @@ mod tests {
     #[test]
     fn preview_result() {
         let a: Result<i32, i32> = Ok(3);
-        assert_eq!(preview(_Ok, a), Some(3));
+        assert_eq!(_Ok(a), Some(3));
 
         let a: Result<i32, i32> = Err(3);
         assert_eq!(preview(_Ok, a), None);
 
         let a: Result<i32, i32> = Ok(3);
-        assert_eq!(preview(_Err, a), None);
+        assert_eq!(_Err(a), None);
 
         let a: Result<i32, i32> = Err(3);
         assert_eq!(preview(_Err, a), Some(3));
@@ -67,7 +87,7 @@ mod tests {
     #[test]
     fn preview_option() {
         let a = Some(3);
-        assert_eq!(preview(_Some, a), Some(3));
+        assert_eq!(_Some(a), Some(3));
 
         let a = Some(3);
         assert_eq!(preview(_None, a), Some(()));
@@ -90,4 +110,11 @@ mod tests {
         assert_eq!(review(_Some, 3), Some(3));
         assert_eq!(review(_None, ()), None::<()>);
     }
+
+    #[test]
+    fn over_option() {
+        assert_eq!(over(_Some, Some(3), |v| v + 1), Some(4));
+        assert_eq!(_Some(Some(3), |v| v + 1), Some(4));
+        assert_eq!(over(_None, None, |_v: ()| ()), None::<()>);
+    }
 }

src/prisms/option.rs

@@ -8,13 +8,11 @@ pub const _Some: Prism<SomeInner> = Prism(SomeInner);
 impl<T> PrismPreview<Option<T>> for SomeInner {
     type Field = T;
 
-    fn preview(thing: Option<T>) -> Option<Self::Field> {
+    fn preview(&self, thing: Option<T>) -> Option<Self::Field> {
         thing
     }
-}
 
-impl<T> PrismReview<Option<T>> for SomeInner {
-    fn review(thing: Self::Field) -> Option<T> {
+    fn review(&self, thing: Self::Field) -> Option<T> {
         Some(thing)
     }
 }
@@ -26,13 +24,11 @@ pub const _None: Prism<NoneInner> = Prism(NoneInner);
 impl<T> PrismPreview<Option<T>> for NoneInner {
     type Field = ();
 
-    fn preview(_thing: Option<T>) -> Option<Self::Field> {
+    fn preview(&self, _thing: Option<T>) -> Option<Self::Field> {
         Some(())
     }
-}
 
-impl<T> PrismReview<Option<T>> for NoneInner {
-    fn review(_thing: Self::Field) -> Option<T> {
+    fn review(&self, _thing: Self::Field) -> Option<T> {
         None
     }
 }

src/prisms/result.rs

@@ -7,13 +7,10 @@ pub const _Ok: Prism<OkInner> = Prism(OkInner);
 impl<T, E> PrismPreview<Result<T, E>> for OkInner {
     type Field = T;
 
-    fn preview(thing: Result<T, E>) -> Option<Self::Field> {
+    fn preview(&self, thing: Result<T, E>) -> Option<Self::Field> {
         thing.ok()
     }
-}
-
-impl<T, E> PrismReview<Result<T, E>> for OkInner {
-    fn review(thing: Self::Field) -> Result<T, E> {
+    fn review(&self, thing: Self::Field) -> Result<T, E> {
         Ok(thing)
     }
 }
@@ -26,13 +23,10 @@ pub const _Err: Prism<ErrInner> = Prism(ErrInner);
 impl<T, E> PrismPreview<Result<T, E>> for ErrInner {
     type Field = E;
 
-    fn preview(thing: Result<T, E>) -> Option<Self::Field> {
+    fn preview(&self, thing: Result<T, E>) -> Option<Self::Field> {
         thing.err()
     }
-}
-
-impl<T, E> PrismReview<Result<T, E>> for ErrInner {
-    fn review(thing: Self::Field) -> Result<T, E> {
+    fn review(&self, thing: Self::Field) -> Result<T, E> {
         Err(thing)
     }
 }

src/traversals/mod.rs

@@ -4,7 +4,10 @@ pub use both::both;
 mod each;
 pub use each::each;
 
-use crate::lenses::{Lens, LensOver, LensView};
+use crate::{
+    lenses::{Lens, LensOver, LensView},
+    prisms::{Prism, PrismPreview},
+};
 
 /// Wrapper type
 #[derive(Clone, Copy)]
@@ -87,6 +90,43 @@ where
     }
 }
 
+// all prisms are traversals, so we can freely transform them into a traversal
+impl<L> Prism<L> {
+    /// Returns this lens as a traversal
+    pub fn to_traversal(self) -> Traversal<Prism<L>> {
+        Traversal(self)
+    }
+}
+// we can go back to a lens from a "traversal-ed" lens
+impl<L> Traversal<Prism<L>> {
+    /// Returns the wrapped lens
+    pub fn to_prism(self) -> Prism<L> {
+        self.0
+    }
+}
+impl<L, T> TraversalTraverse<T> for Prism<L>
+where
+    L: PrismPreview<T>,
+{
+    type Field = L::Field;
+
+    fn traverse(&self, thing: T) -> Vec<Self::Field> {
+        L::preview(&self.0, thing).into_iter().collect()
+    }
+}
+impl<L, T> TraversalOver<T> for Prism<L>
+where
+    T: Clone,
+    L: PrismPreview<T>,
+{
+    fn over<F>(&self, thing: T, f: F) -> T
+    where
+        F: FnMut(Self::Field) -> Self::Field,
+    {
+        L::over(&self.0, thing, f)
+    }
+}
+
 pub fn traverse<T, L: TraversalTraverse<T>>(lens: L, thing: T) -> Vec<L::Field> {
     L::traverse(&lens, thing)
 }
@@ -102,7 +142,7 @@ pub fn over<T, L: TraversalOver<T>>(lens: L, thing: T, f: impl FnMut(L::Field) -
 
 #[cfg(test)]
 mod tests {
-    use crate::lenses::_0;
+    use crate::{lenses::_0, prisms::_Some};
 
     use super::*;
 
@@ -157,4 +197,45 @@ mod tests {
         let res = t(array, |v| v + 1);
         assert_eq!(res, [(2, 3), (3, 4), (5, 6)]);
     }
+
+    #[test]
+    fn can_combine_prism_with_traversal() {
+        let array = [Some(1), None, Some(3), None, Some(5)];
+
+        // combine a traversal with a lens
+        let t = each + _Some;
+
+        // traverse
+        let res = t(array);
+        assert_eq!(res, vec![1, 3, 5]);
+
+        // over
+        let res = t(array, |v| v + 1);
+        assert_eq!(res, [Some(2), None, Some(4), None, Some(6)]);
+    }
+
+    #[test]
+    fn can_combine_traversal_with_prism() {
+        let array = Some([1, 2, 3]);
+
+        // combine a traversal with a lens
+        let t = _Some + each;
+
+        // traverse
+        let res = t(array);
+        assert_eq!(res, vec![1, 2, 3]);
+
+        // over
+        let res = t(array, |v| v + 1);
+        assert_eq!(res, Some([2, 3, 4]));
+
+        let array: Option<[i32; 3]> = None;
+        // traverse
+        let res = t(array);
+        assert_eq!(res, vec![]);
+
+        // over
+        let res = t(array, |v| v + 1);
+        assert_eq!(res, None);
+    }
 }