flip: overload without axis (mimics NumPy)

Author: tdegeus

include/xtensor/xmanipulation.hpp

@@ -76,6 +76,9 @@ namespace xt
     template <class E>
     auto vsplit(E& e, std::size_t n);
 
+    template <class E>
+    auto flip(E&& e);
+
     template <class E>
     auto flip(E&& e, std::size_t axis);
 
@@ -589,7 +592,7 @@ namespace xt
     /**
      * @brief Split an xexpression into subexpressions horizontally (column-wise)
      *
-     * This method is equivalent to ``split(e, n, 1)``. 
+     * This method is equivalent to ``split(e, n, 1)``.
      *
      * @param e input xexpression
      * @param n number of elements to return
@@ -618,6 +621,24 @@ namespace xt
      * flip implementation *
      ***********************/
 
+    /**
+     * @brief Reverse the order of elements in an xexpression along every axis.
+     *
+     * @param e the input xexpression
+     *
+     * @return returns a view with the result of the flip.
+     */
+    template <class E>
+    inline auto flip(E&& e)
+    {
+        using size_type = typename std::decay_t<E>::size_type;
+        auto r = flip(e, 0);
+        for (size_type d = 1; d < e.dimension(); ++d) {
+            r = flip(r, d);
+        }
+        return r;
+    }
+
     /**
      * @brief Reverse the order of elements in an xexpression along the given axis.
      * Note: A NumPy/Matlab style `flipud(arr)` is equivalent to `xt::flip(arr, 0)`,
@@ -902,7 +923,7 @@ namespace xt
      * @brief Repeats elements of an expression along a given axis.
      *
      * @param e the input xexpression
-     * @param repeats The number of repetition of each elements. The size of \ref repeats 
+     * @param repeats The number of repetition of each elements. The size of \ref repeats
      * must match the shape of the given \ref axis.
      * @param axis the axis along which to repeat the value
      *
@@ -918,7 +939,7 @@ namespace xt
      * @brief Repeats elements of an expression along a given axis.
      *
      * @param e the input xexpression
-     * @param repeats The number of repetition of each elements. The size of \ref repeats 
+     * @param repeats The number of repetition of each elements. The size of \ref repeats
      * must match the shape of the given \ref axis.
      * @param axis the axis along which to repeat the value
      *

test/test_xmanipulation.cpp

@@ -153,7 +153,7 @@ namespace xt
             auto e = flatten<XTENSOR_DEFAULT_LAYOUT>(a);
             xtensor<double, 1> fl = e;
             using assign_traits = xassign_traits<decltype(fl), decltype(e)>;
-        
+
         #if XTENSOR_USE_XSIMD
             EXPECT_TRUE(assign_traits::simd_linear_assign());
             EXPECT_TRUE(assign_traits::simd_linear_assign(fl, e));
@@ -397,6 +397,22 @@ namespace xt
         ASSERT_EQ(expected_2, ft);
     }
 
+    TEST(xmanipulation, flip_noaxis)
+    {
+        {
+            xtensor<double, 1> e = {1, 2, 3, 4, 5, 6};
+            xtensor<double, 1> t = xt::flip(e);
+            xtensor<double, 1> expected = {6, 5, 4, 3, 2, 1};
+            ASSERT_EQ(expected, t);
+        }
+        {
+            xtensor<double, 2> e = {{1, 2, 3}, {4, 5, 6}};
+            xtensor<double, 2> t = xt::flip(e);
+            xtensor<double, 2> expected = {{6, 5, 4}, {3, 2, 1}};
+            ASSERT_EQ(expected, t);
+        }
+    }
+
     TEST(xmanipulation, rot90)
     {
         xarray<double> e = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};