Check ndim in check_trailing_shape helpers

This was previously checked by using an `array_view<type, ndim>`, but
moving to pybind11 we won't have that until cast to `unchecked`.

Author: QuLogic

src/mplutils.h

@@ -71,6 +71,12 @@ inline int prepare_and_add_type(PyTypeObject *type, PyObject *module)
 template<typename T>
 inline bool check_trailing_shape(T array, char const* name, long d1)
 {
+    if (array.ndim() != 2) {
+        PyErr_Format(PyExc_ValueError,
+                     "Expected 2-dimensional array, got %ld",
+                     array.ndim());
+        return false;
+    }
     if (array.shape(1) != d1) {
         PyErr_Format(PyExc_ValueError,
                      "%s must have shape (N, %ld), got (%ld, %ld)",
@@ -83,6 +89,12 @@ inline bool check_trailing_shape(T array, char const* name, long d1)
 template<typename T>
 inline bool check_trailing_shape(T array, char const* name, long d1, long d2)
 {
+    if (array.ndim() != 3) {
+        PyErr_Format(PyExc_ValueError,
+                     "Expected 3-dimensional array, got %ld",
+                     array.ndim());
+        return false;
+    }
     if (array.shape(1) != d1 || array.shape(2) != d2) {
         PyErr_Format(PyExc_ValueError,
                      "%s must have shape (N, %ld, %ld), got (%ld, %ld, %ld)",

src/numpy_cpp.h

@@ -365,10 +365,6 @@ class array_view : public detail::array_view_accessors<array_view, T, ND>
   public:
     typedef T value_type;
 
-    enum {
-        ndim = ND
-    };
-
     array_view() : m_arr(NULL), m_data(NULL)
     {
         m_shape = zeros;
@@ -492,6 +488,10 @@ class array_view : public detail::array_view_accessors<array_view, T, ND>
         return true;
     }
 
+    npy_intp ndim() const {
+        return ND;
+    }
+
     npy_intp shape(size_t i) const
     {
         if (i >= ND) {