Add From implementations.

src/traits.rs

@@ -59,3 +59,18 @@ impl<'a,T> Strided for MutStride<'a,T> {
 impl<'a,T> MutStrided for MutStride<'a,T> {
     fn as_stride_mut(&mut self) -> MutStride<T> { self.reborrow() }
 }
+
+// this isn't as general as it could be.
+impl<'a,T, X: Deref<Target=[T]>> From<&'a X> for Stride<'a,T> {
+    fn from(value: &X) -> Stride<T> { Stride::new(&**value) }
+}
+impl<'a,T, X: DerefMut + Deref<Target=[T]>> From<&'a mut X> for MutStride<'a,T> {
+    fn from(value: &mut X) -> MutStride<T> { MutStride::new(&mut **value) }
+}
+
+impl<'a,T> From<&'a [T]> for Stride<'a,T> {
+    fn from(value: &[T]) -> Stride<T> { Stride::new(value) }
+}
+impl<'a,T> From<&'a mut [T]> for MutStride<'a,T> {
+    fn from(value: &mut [T]) -> MutStride<T> { MutStride::new(value) }
+}