FIX: Remove broadcast_shape from the DimMax trait

While calling co_broadcast directly is less convenient, for now they are
two different functions.

src/dimension/broadcast.rs

@@ -6,11 +6,11 @@ use crate::{Dimension, Ix0, Ix1, Ix2, Ix3, Ix4, Ix5, Ix6, IxDyn};
 ///
 /// Uses the [NumPy broadcasting rules]
 //  (https://docs.scipy.org/doc/numpy/user/basics.broadcasting.html#general-broadcasting-rules).
-fn co_broadcast<D1, D2, Output>(shape1: &D1, shape2: &D2) -> Result<Output, ShapeError>
-    where
-        D1: Dimension,
-        D2: Dimension,
-        Output: Dimension,
+pub(crate) fn co_broadcast<D1, D2, Output>(shape1: &D1, shape2: &D2) -> Result<Output, ShapeError>
+where
+    D1: Dimension,
+    D2: Dimension,
+    Output: Dimension,
 {
     let (k, overflow) = shape1.ndim().overflowing_sub(shape2.ndim());
     // Swap the order if d2 is longer.
@@ -37,40 +37,23 @@ fn co_broadcast<D1, D2, Output>(shape1: &D1, shape2: &D2) -> Result<Output, Shap
 pub trait DimMax<Other: Dimension> {
     /// The resulting dimension type after broadcasting.
     type Output: Dimension;
-
-    /// Determines the shape after broadcasting the shapes together.
-    ///
-    /// If the shapes are not compatible, returns `Err`.
-    fn broadcast_shape(&self, other: &Other) -> Result<Self::Output, ShapeError>;
 }
 
 /// Dimensions of the same type remain unchanged when co_broadcast.
 /// So you can directly use D as the resulting type.
 /// (Instead of <D as DimMax<D>>::BroadcastOutput)
 impl<D: Dimension> DimMax<D> for D {
     type Output = D;
-
-    fn broadcast_shape(&self, other: &D) -> Result<Self::Output, ShapeError> {
-        co_broadcast::<D, D, Self::Output>(self, other)
-    }
 }
 
 macro_rules! impl_broadcast_distinct_fixed {
     ($smaller:ty, $larger:ty) => {
         impl DimMax<$larger> for $smaller {
             type Output = $larger;
-
-            fn broadcast_shape(&self, other: &$larger) -> Result<Self::Output, ShapeError> {
-                co_broadcast::<Self, $larger, Self::Output>(self, other)
-            }
         }
 
         impl DimMax<$smaller> for $larger {
             type Output = $larger;
-
-            fn broadcast_shape(&self, other: &$smaller) -> Result<Self::Output, ShapeError> {
-                co_broadcast::<Self, $smaller, Self::Output>(self, other)
-            }
         }
     };
 }
@@ -103,3 +86,58 @@ impl_broadcast_distinct_fixed!(Ix3, IxDyn);
 impl_broadcast_distinct_fixed!(Ix4, IxDyn);
 impl_broadcast_distinct_fixed!(Ix5, IxDyn);
 impl_broadcast_distinct_fixed!(Ix6, IxDyn);
+
+
+#[cfg(test)]
+#[cfg(feature = "std")]
+mod tests {
+    use super::co_broadcast;
+    use crate::{Dimension, Dim, DimMax, ShapeError, Ix0, IxDynImpl, ErrorKind};
+
+    #[test]
+    fn test_broadcast_shape() {
+        fn test_co<D1, D2>(
+            d1: &D1,
+            d2: &D2,
+            r: Result<<D1 as DimMax<D2>>::Output, ShapeError>,
+        ) where
+            D1: Dimension + DimMax<D2>,
+            D2: Dimension,
+        {
+            let d = co_broadcast::<D1, D2, <D1 as DimMax<D2>>::Output>(&d1, d2);
+            assert_eq!(d, r);
+        }
+        test_co(&Dim([2, 3]), &Dim([4, 1, 3]), Ok(Dim([4, 2, 3])));
+        test_co(
+            &Dim([1, 2, 2]),
+            &Dim([1, 3, 4]),
+            Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
+        );
+        test_co(&Dim([3, 4, 5]), &Ix0(), Ok(Dim([3, 4, 5])));
+        let v = vec![1, 2, 3, 4, 5, 6, 7];
+        test_co(
+            &Dim(vec![1, 1, 3, 1, 5, 1, 7]),
+            &Dim([2, 1, 4, 1, 6, 1]),
+            Ok(Dim(IxDynImpl::from(v.as_slice()))),
+        );
+        let d = Dim([1, 2, 1, 3]);
+        test_co(&d, &d, Ok(d));
+        test_co(
+            &Dim([2, 1, 2]).into_dyn(),
+            &Dim(0),
+            Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
+        );
+        test_co(
+            &Dim([2, 1, 1]),
+            &Dim([0, 0, 1, 3, 4]),
+            Ok(Dim([0, 0, 2, 3, 4])),
+        );
+        test_co(&Dim([0]), &Dim([0, 0, 0]), Ok(Dim([0, 0, 0])));
+        test_co(&Dim(1), &Dim([1, 0, 0]), Ok(Dim([1, 0, 0])));
+        test_co(
+            &Dim([1, 3, 0, 1, 1]),
+            &Dim([1, 2, 3, 1]),
+            Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
+        );
+    }
+}

src/dimension/mod.rs

@@ -29,7 +29,7 @@ use std::mem;
 mod macros;
 mod axes;
 mod axis;
-mod broadcast;
+pub(crate) mod broadcast;
 mod conversion;
 pub mod dim;
 mod dimension_trait;

src/impl_methods.rs

@@ -21,6 +21,7 @@ use crate::dimension::{
     abs_index, axes_of, do_slice, merge_axes, move_min_stride_axis_to_last,
     offset_from_ptr_to_memory, size_of_shape_checked, stride_offset, Axes,
 };
+use crate::dimension::broadcast::co_broadcast;
 use crate::error::{self, ErrorKind, ShapeError, from_kind};
 use crate::math_cell::MathCell;
 use crate::itertools::zip;
@@ -1778,7 +1779,7 @@ where
         D: Dimension + DimMax<E>,
         E: Dimension,
     {
-        let shape = self.dim.broadcast_shape(&other.dim)?;
+        let shape = co_broadcast::<D, E, <D as DimMax<E>>::Output>(&self.dim, &other.dim)?;
         if let Some(view1) = self.broadcast(shape.clone()) {
             if let Some(view2) = other.broadcast(shape) {
                 return Ok((view1, view2))

tests/dimension.rs

@@ -2,8 +2,7 @@
 
 use defmac::defmac;
 
-use ndarray::{arr2, ArcArray, Array, Axis, Dim, Dimension, Ix0, IxDyn, IxDynImpl, RemoveAxis,
-              ErrorKind, ShapeError, DimMax};
+use ndarray::{arr2, ArcArray, Array, Axis, Dim, Dimension, IxDyn, RemoveAxis};
 
 use std::hash::{Hash, Hasher};
 
@@ -341,50 +340,3 @@ fn test_all_ndindex() {
     ndindex!(10, 4, 3, 2, 2);
     ndindex!(10, 4, 3, 2, 2, 2);
 }
-
-#[test]
-fn test_broadcast_shape() {
-    fn test_co<D1, D2>(
-        d1: &D1,
-        d2: &D2,
-        r: Result<<D1 as DimMax<D2>>::Output, ShapeError>,
-    ) where
-        D1: Dimension + DimMax<D2>,
-        D2: Dimension,
-    {
-        let d = d1.broadcast_shape(d2);
-        assert_eq!(d, r);
-    }
-    test_co(&Dim([2, 3]), &Dim([4, 1, 3]), Ok(Dim([4, 2, 3])));
-    test_co(
-        &Dim([1, 2, 2]),
-        &Dim([1, 3, 4]),
-        Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
-    );
-    test_co(&Dim([3, 4, 5]), &Ix0(), Ok(Dim([3, 4, 5])));
-    let v = vec![1, 2, 3, 4, 5, 6, 7];
-    test_co(
-        &Dim(vec![1, 1, 3, 1, 5, 1, 7]),
-        &Dim([2, 1, 4, 1, 6, 1]),
-        Ok(Dim(IxDynImpl::from(v.as_slice()))),
-    );
-    let d = Dim([1, 2, 1, 3]);
-    test_co(&d, &d, Ok(d));
-    test_co(
-        &Dim([2, 1, 2]).into_dyn(),
-        &Dim(0),
-        Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
-    );
-    test_co(
-        &Dim([2, 1, 1]),
-        &Dim([0, 0, 1, 3, 4]),
-        Ok(Dim([0, 0, 2, 3, 4])),
-    );
-    test_co(&Dim([0]), &Dim([0, 0, 0]), Ok(Dim([0, 0, 0])));
-    test_co(&Dim(1), &Dim([1, 0, 0]), Ok(Dim([1, 0, 0])));
-    test_co(
-        &Dim([1, 3, 0, 1, 1]),
-        &Dim([1, 2, 3, 1]),
-        Err(ShapeError::from_kind(ErrorKind::IncompatibleShape)),
-    );
-}