From a434f18ba4ccdeba0e096daf20f8a0ee082739d3 Mon Sep 17 00:00:00 2001
From: Brendan Zabarauskas <bjzaba@yahoo.com.au>
Date: Tue, 3 Nov 2015 14:15:11 +1100
Subject: [PATCH] Make array type parameters associated types

---
 src/array.rs      | 31 +++++++++++++++++++++----------
 src/matrix.rs     | 22 ++++++++++++++++++----
 src/point.rs      | 10 +++++++---
 src/quaternion.rs |  4 +++-
 src/vector.rs     |  6 ++++--
 5 files changed, 53 insertions(+), 20 deletions(-)

diff --git a/src/array.rs b/src/array.rs
index f2e0e59..0bbfd32 100644
--- a/src/array.rs
+++ b/src/array.rs
@@ -18,14 +18,19 @@ use std::ptr;
 use std::ops::*;
 
 /// An array containing elements of type `Element`
-pub trait Array1<Element: Copy>: Index<usize, Output=Element> + IndexMut<usize, Output=Element> {
+pub trait Array1 where
+    Self: Index<usize, Output = <Self as Array1>::Element>,
+    Self: IndexMut<usize, Output = <Self as Array1>::Element>,
+{
+    type Element: Copy;
+
     /// Get the pointer to the first element of the array.
-    fn ptr<'a>(&'a self) -> &'a Element {
+    fn ptr<'a>(&'a self) -> &'a Self::Element {
         &self[0]
     }
 
     /// Get a mutable pointer to the first element of the array.
-    fn mut_ptr<'a>(&'a mut self) -> &'a mut Element {
+    fn mut_ptr<'a>(&'a mut self) -> &'a mut Self::Element {
         &mut self[0]
     }
 
@@ -38,21 +43,27 @@ pub trait Array1<Element: Copy>: Index<usize, Output=Element> + IndexMut<usize,
 
     /// Replace an element in the array.
     #[inline]
-    fn replace_elem(&mut self, i: usize, src: Element) -> Element {
+    fn replace_elem(&mut self, i: usize, src: Self::Element) -> Self::Element {
         mem::replace(&mut self[i], src)
     }
 }
 
 /// A column-major array
-pub trait Array2<Column: Array1<Element>+'static, Row: Array1<Element>, Element: Copy>:
-        Index<usize, Output=Column> + IndexMut<usize, Output=Column> {
+pub trait Array2 where
+    Self: Index<usize, Output = <Self as Array2>::Column>,
+    Self: IndexMut<usize, Output = <Self as Array2>::Column>,
+{
+    type Element: Copy;
+    type Column: Array1<Element = Self::Element>;
+    type Row: Array1<Element = Self::Element>;
+
     /// Get the pointer to the first element of the array.
-    fn ptr<'a>(&'a self) -> &'a Element {
+    fn ptr<'a>(&'a self) -> &'a Self::Element {
         &self[0][0]
     }
 
     /// Get a mutable pointer to the first element of the array.
-    fn mut_ptr<'a>(&'a mut self) -> &'a mut Element {
+    fn mut_ptr<'a>(&'a mut self) -> &'a mut Self::Element {
         &mut self[0][0]
     }
 
@@ -64,12 +75,12 @@ pub trait Array2<Column: Array1<Element>+'static, Row: Array1<Element>, Element:
 
     /// Replace a column in the array.
     #[inline]
-    fn replace_col(&mut self, c: usize, src: Column) -> Column {
+    fn replace_col(&mut self, c: usize, src: Self::Column) -> Self::Column {
         mem::replace(&mut self[c], src)
     }
 
     /// Get a row from this array by-value.
-    fn row(&self, r: usize) -> Row;
+    fn row(&self, r: usize) -> Self::Row;
 
     /// Swap two rows of this array.
     fn swap_rows(&mut self, a: usize, b: usize);
diff --git a/src/matrix.rs b/src/matrix.rs
index 3fd337c..5b05ab8 100644
--- a/src/matrix.rs
+++ b/src/matrix.rs
@@ -249,7 +249,9 @@ impl<S: Copy + Neg<Output = S>> Matrix4<S> {
     }
 }
 
-pub trait Matrix<S: BaseFloat, V: Vector<S> + 'static>: Array2<V, V, S> + ApproxEq<Epsilon = S> + Sized // where
+pub trait Matrix<S: BaseFloat, V: Vector<S>> where
+    Self: Array2<Element = S, Column = V, Row = V>,
+    Self: ApproxEq<Epsilon = S> + Sized,
     // FIXME: blocked by rust-lang/rust#20671
     //
     // for<'a, 'b> &'a Self: Add<&'b Self, Output = Self>,
@@ -359,7 +361,11 @@ pub trait Matrix<S: BaseFloat, V: Vector<S> + 'static>: Array2<V, V, S> + Approx
     fn is_symmetric(&self) -> bool;
 }
 
-impl<S: Copy + 'static> Array2<Vector2<S>, Vector2<S>, S> for Matrix2<S> {
+impl<S: Copy + 'static> Array2 for Matrix2<S> {
+    type Element = S;
+    type Column = Vector2<S>;
+    type Row = Vector2<S>;
+
     #[inline]
     fn row(&self, r: usize) -> Vector2<S> {
         Vector2::new(self[0][r],
@@ -373,7 +379,11 @@ impl<S: Copy + 'static> Array2<Vector2<S>, Vector2<S>, S> for Matrix2<S> {
     }
 }
 
-impl<S: Copy + 'static> Array2<Vector3<S>, Vector3<S>, S> for Matrix3<S> {
+impl<S: Copy + 'static> Array2 for Matrix3<S> {
+    type Element = S;
+    type Column = Vector3<S>;
+    type Row = Vector3<S>;
+
     #[inline]
     fn row(&self, r: usize) -> Vector3<S> {
         Vector3::new(self[0][r],
@@ -389,7 +399,11 @@ impl<S: Copy + 'static> Array2<Vector3<S>, Vector3<S>, S> for Matrix3<S> {
     }
 }
 
-impl<S: Copy + 'static> Array2<Vector4<S>, Vector4<S>, S> for Matrix4<S> {
+impl<S: Copy + 'static> Array2 for Matrix4<S> {
+    type Element = S;
+    type Column = Vector4<S>;
+    type Row = Vector4<S>;
+
     #[inline]
     fn row(&self, r: usize) -> Vector4<S> {
         Vector4::new(self[0][r],
diff --git a/src/point.rs b/src/point.rs
index 1f917f1..809c94d 100644
--- a/src/point.rs
+++ b/src/point.rs
@@ -66,7 +66,7 @@ impl<S: BaseNum> Point3<S> {
 }
 
 /// Specifies the numeric operations for point types.
-pub trait Point<S: BaseNum>: Array1<S> + Clone // where
+pub trait Point<S: BaseNum>: Array1<Element = S> + Clone // where
     // FIXME: blocked by rust-lang/rust#20671
     //
     // for<'a, 'b> &'a Self: Add<&'b V, Output = Self>,
@@ -123,7 +123,9 @@ pub trait Point<S: BaseNum>: Array1<S> + Clone // where
     fn max(&self, p: &Self) -> Self;
 }
 
-impl<S: BaseNum> Array1<S> for Point2<S> {}
+impl<S: BaseNum> Array1 for Point2<S> {
+    type Element = S;
+}
 
 impl<S: BaseNum> Point<S> for Point2<S> {
     type Vector = Vector2<S>;
@@ -200,7 +202,9 @@ impl<S: BaseFloat> ApproxEq for Point2<S> {
     }
 }
 
-impl<S: BaseNum> Array1<S> for Point3<S> {}
+impl<S: BaseNum> Array1 for Point3<S> {
+    type Element = S;
+}
 
 impl<S: BaseNum> Point<S> for Point3<S> {
     type Vector = Vector3<S>;
diff --git a/src/quaternion.rs b/src/quaternion.rs
index 51802e8..6c9635a 100644
--- a/src/quaternion.rs
+++ b/src/quaternion.rs
@@ -40,7 +40,9 @@ pub struct Quaternion<S> {
     pub v: Vector3<S>,
 }
 
-impl<S: Copy + BaseFloat> Array1<S> for Quaternion<S> {}
+impl<S: Copy + BaseFloat> Array1 for Quaternion<S> {
+    type Element = S;
+}
 
 impl<S: BaseFloat> Quaternion<S> {
     /// Construct a new quaternion from one scalar component and three
diff --git a/src/vector.rs b/src/vector.rs
index fa13ea5..77e63f1 100644
--- a/src/vector.rs
+++ b/src/vector.rs
@@ -111,7 +111,7 @@ use num::{BaseNum, BaseFloat};
 /// A trait that specifies a range of numeric operations for vectors. Not all
 /// of these make sense from a linear algebra point of view, but are included
 /// for pragmatic reasons.
-pub trait Vector<S: BaseNum>: Array1<S> + Clone // where
+pub trait Vector<S: BaseNum>: Array1<Element = S> + Clone // where
     // FIXME: blocked by rust-lang/rust#20671
     //
     // for<'a, 'b> &'a Self: Add<&'b Self, Output = Self>,
@@ -245,7 +245,9 @@ macro_rules! vec {
             }
         }
 
-        impl<$S: Copy> Array1<$S> for $VectorN<$S> {}
+        impl<S: Copy> Array1 for $VectorN<S> {
+            type Element = S;
+        }
 
         impl<S: BaseNum> Vector<S> for $VectorN<S> {
             #[inline] fn from_value(s: S) -> $VectorN<S> { $VectorN { $($field: s),+ } }