Add squeeze() to dynamic dimension arrays

src/impl_dyn.rs

@@ -58,4 +58,60 @@ where S: Data<Elem = A>
         self.dim = self.dim.remove_axis(axis);
         self.strides = self.strides.remove_axis(axis);
     }
+
+    /// Remove axes of length 1 and return the modified array.
+    ///
+    /// If the array has more the one dimension, the result array will always
+    /// have at least one dimension, even if it has a length of 1.
+    ///
+    /// ```
+    /// use ndarray::{arr1, arr2, arr3};
+    ///
+    /// let a = arr3(&[[[1, 2, 3]], [[4, 5, 6]]]).into_dyn();
+    /// assert_eq!(a.shape(), &[2, 1, 3]);
+    /// let b = a.squeeze();
+    /// assert_eq!(b, arr2(&[[1, 2, 3], [4, 5, 6]]).into_dyn());
+    /// assert_eq!(b.shape(), &[2, 3]);
+    ///
+    /// let c = arr2(&[[1]]).into_dyn();
+    /// assert_eq!(c.shape(), &[1, 1]);
+    /// let d = c.squeeze();
+    /// assert_eq!(d, arr1(&[1]).into_dyn());
+    /// assert_eq!(d.shape(), &[1]);
+    /// ```
+    #[track_caller]
+    pub fn squeeze(self) -> Self
+    {
+        let mut out = self;
+        for axis in (0..out.shape().len()).rev() {
+            if out.shape()[axis] == 1 && out.shape().len() > 1 {
+                out = out.remove_axis(Axis(axis));
+            }
+        }
+        out
+    }
+}
+
+#[cfg(test)]
+mod tests
+{
+    use crate::{arr1, arr2, arr3};
+
+    #[test]
+    fn test_squeeze()
+    {
+        let a = arr3(&[[[1, 2, 3]], [[4, 5, 6]]]).into_dyn();
+        assert_eq!(a.shape(), &[2, 1, 3]);
+
+        let b = a.squeeze();
+        assert_eq!(b, arr2(&[[1, 2, 3], [4, 5, 6]]).into_dyn());
+        assert_eq!(b.shape(), &[2, 3]);
+
+        let c = arr2(&[[1]]).into_dyn();
+        assert_eq!(c.shape(), &[1, 1]);
+
+        let d = c.squeeze();
+        assert_eq!(d, arr1(&[1]).into_dyn());
+        assert_eq!(d.shape(), &[1]);
+    }
 }