Add const vs. dynamic ndim to array Debug format

The difference between const-dimensional and dynamic-dimensional
arrays is fairly significant, so it is useful for the debug format to
include this information.

Author: jturner314

src/arrayformat.rs

@@ -105,9 +105,13 @@ impl<'a, A: fmt::Debug, S, D: Dimension> fmt::Debug for ArrayBase<S, D>
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // Add extra information for Debug
-        try!(format_array(self, f, <_>::fmt));
-        try!(write!(f, " shape={:?}, strides={:?}, layout={:?}",
-                    self.shape(), self.strides(), layout=self.view().layout()));
+        format_array(self, f, <_>::fmt)?;
+        write!(f, " shape={:?}, strides={:?}, layout={:?}",
+               self.shape(), self.strides(), layout=self.view().layout())?;
+        match D::NDIM {
+            Some(ndim) => write!(f, ", const ndim={}", ndim)?,
+            None => write!(f, ", dynamic ndim={}", self.ndim())?,
+        }
         Ok(())
     }
 }

tests/format.rs

@@ -1,7 +1,7 @@
-
 extern crate ndarray;
 
-use ndarray::{arr0, rcarr1, aview1};
+use ndarray::prelude::*;
+use ndarray::rcarr1;
 
 #[test]
 fn formatting()
@@ -35,3 +35,20 @@ fn formatting()
     let s = format!("{:02x}", aview1::<u8>(&[1, 0xff, 0xfe]));
     assert_eq!(s, "[01, ff, fe]");
 }
+
+#[test]
+fn debug_format() {
+    let a = Array2::<i32>::zeros((3, 4));
+    assert_eq!(
+        format!("{:?}", a),
+        "[[0, 0, 0, 0],
+ [0, 0, 0, 0],
+ [0, 0, 0, 0]] shape=[3, 4], strides=[4, 1], layout=C (0x1), const ndim=2"
+    );
+    assert_eq!(
+        format!("{:?}", a.into_dyn()),
+        "[[0, 0, 0, 0],
+ [0, 0, 0, 0],
+ [0, 0, 0, 0]] shape=[3, 4], strides=[4, 1], layout=C (0x1), dynamic ndim=2"
+    );
+}