Merge pull request #546 from rust-ndarray/fold-axis-check-axis

fold axis: Include panic on axis oob in doc

Author: bluss

src/dimension/remove_axis.rs

@@ -19,7 +19,10 @@ pub trait RemoveAxis : Dimension {
 
 impl RemoveAxis for Dim<[Ix; 1]> {
     #[inline]
-    fn remove_axis(&self, _: Axis) -> Ix0 { Ix0() }
+    fn remove_axis(&self, axis: Axis) -> Ix0 {
+        debug_assert!(axis.index() < self.ndim());
+        Ix0()
+    }
 }
 
 impl RemoveAxis for Dim<[Ix; 2]> {
@@ -38,6 +41,7 @@ macro_rules! impl_remove_axis_array(
         {
             #[inline]
             fn remove_axis(&self, axis: Axis) -> Self::Smaller {
+                debug_assert!(axis.index() < self.ndim());
                 let mut tup = Dim([0; $n - 1]);
                 {
                     let mut it = tup.slice_mut().iter_mut();

src/impl_methods.rs

@@ -1849,6 +1849,8 @@ impl<A, S, D> ArrayBase<S, D> where S: Data<Elem=A>, D: Dimension
     /// function and initial value `init`.
     ///
     /// Return the result as an `Array`.
+    ///
+    /// **Panics** if `axis` is out of bounds.
     pub fn fold_axis<B, F>(&self, axis: Axis, init: B, mut fold: F)
         -> Array<B, D::Smaller>
         where D: RemoveAxis,

tests/higher_order_f.rs

@@ -0,0 +1,11 @@
+
+extern crate ndarray;
+
+use ndarray::prelude::*;
+
+#[test]
+#[should_panic]
+fn test_fold_axis_oob() {
+    let a = arr2(&[[1., 2.], [3., 4.]]);
+    a.fold_axis(Axis(2), 0., |x, y| x + y);
+}