# HG changeset patch
# User Tuomo Valkonen <tuomov@iki.fi>
# Date 1697224556 18000
# Node ID 8de8a80852c2db2e2857df6243bc1f434f96af85
# Parent  239aa32f0e7df91fc40ae18bed0e0c8aebbb84f9
diff_ref

diff -r 239aa32f0e7d -r 8de8a80852c2 src/mapping.rs
--- a/src/mapping.rs	Mon Oct 21 09:59:45 2024 -0500
+++ b/src/mapping.rs	Fri Oct 13 14:15:56 2023 -0500
@@ -88,6 +88,11 @@
     fn diff(self) -> Differential<Domain, Self> {
         Differential{ g : self, _space : PhantomData }
     }
+
+    /// Form the differential mapping of `self`.
+    fn diff_ref(&self) -> Differential<Domain, Ref<'_, Self>> {
+        Differential{ g : Ref(self), _space : PhantomData }
+    }
 }
 
 
@@ -242,9 +247,35 @@
         assert!(slice < N);
         SlicedCodomain{ g : self, slice, _phantoms : PhantomData }
     }
+
+    /// Flatten the codomain from [`Loc`]`<F, 1>` to `F`.
+    fn slice_codomain_ref(&self, slice : usize) -> SlicedCodomain<X, F, Ref<'_, Self>, N> {
+        assert!(slice < N);
+        SlicedCodomain{ g : Ref(self), slice, _phantoms : PhantomData }
+    }
 }
 
 impl<X, F : Copy, G : Sized + Mapping<X, Codomain=Loc<F, N>>, const N : usize>
 SliceCodomain<X, F, N>
 for G {}
 
+
+/// Helper struct for doing operations on references of mappings while avoiding
+/// conflicting implementations that `&'g G` would cause.
+pub struct Ref<'g, G>(&'g G);
+
+impl<'g, X, G : Apply<X>> Apply<X> for Ref<'g, G> {
+    type Output = G::Output;
+    #[inline]
+    fn apply(&self, x : X) -> Self::Output {
+        self.0.apply(x)
+    }
+}
+
+impl<'g, X, G : Differentiable<X>> Differentiable<X> for Ref<'g, G> {
+    type Output = G::Output;
+    #[inline]
+    fn differential(&self, x : X) -> Self::Output {
+        self.0.differential(x)
+    }
+}