xtensor-stack · tdegeus · Jun 3, 2021 · Jun 3, 2021
diff --git a/.azure-pipelines/unix-build.yml b/.azure-pipelines/unix-build.yml
@@ -42,6 +42,14 @@ steps:
     displayName: Example - readme 1
     workingDirectory: $(Build.SourcesDirectory)/docs/source/examples/readme_example_1
 
+  - script: |
+      source activate xtensor-python
+      cmake . -DPYTHON_EXECUTABLE=`which python`
+      cmake --build .
+      python example.py
+    displayName: Example - Copy 'cast'
+    workingDirectory: $(Build.SourcesDirectory)/docs/source/examples/copy_cast
+
   - script: |
       source activate xtensor-python
       cmake . -DPYTHON_EXECUTABLE=`which python`

diff --git a/docs/source/examples/copy_cast/CMakeLists.txt b/docs/source/examples/copy_cast/CMakeLists.txt
@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.1..3.19)
+
+project(mymodule)
+
+find_package(pybind11 CONFIG REQUIRED)
+find_package(xtensor REQUIRED)
+find_package(xtensor-python REQUIRED)
+find_package(Python REQUIRED COMPONENTS NumPy)
+
+pybind11_add_module(mymodule main.cpp)
+target_link_libraries(mymodule PUBLIC pybind11::module xtensor-python Python::NumPy)
+
+target_compile_definitions(mymodule PRIVATE VERSION_INFO=0.1.0)
diff --git a/docs/source/examples/copy_cast/example.py b/docs/source/examples/copy_cast/example.py
@@ -0,0 +1,7 @@
+import mymodule
+import numpy as np
+
+a = np.array([1, 2, 3])
+assert np.isclose(np.sum(np.sin(a)), mymodule.sum_of_sines(a))
+assert np.isclose(np.sum(np.cos(a)), mymodule.sum_of_cosines(a))
+
diff --git a/docs/source/examples/copy_cast/main.cpp b/docs/source/examples/copy_cast/main.cpp
@@ -0,0 +1,25 @@
+#include <numeric>
+#include <xtensor.hpp>
+#include <pybind11/pybind11.h>
+#define FORCE_IMPORT_ARRAY
+#include <xtensor-python/pyarray.hpp>
+
+double sum_of_sines(xt::pyarray<double>& m)
+{
+    auto sines = xt::sin(m);  // sines does not actually hold values.
+    return std::accumulate(sines.begin(), sines.end(), 0.0);
+}
+
+double sum_of_cosines(const xt::xarray<double>& m)
+{
+    auto cosines = xt::cos(m);  // cosines does not actually hold values.
+    return std::accumulate(cosines.begin(), cosines.end(), 0.0);
+}
+
+PYBIND11_MODULE(mymodule, m)
+{
+    xt::import_numpy();
+    m.doc() = "Test module for xtensor python bindings";
+    m.def("sum_of_sines", sum_of_sines, "Sum the sines of the input values");
+    m.def("sum_of_cosines", sum_of_cosines, "Sum the cosines of the input values");
+}
diff --git a/include/xtensor-python/xtensor_type_caster_base.hpp b/include/xtensor-python/xtensor_type_caster_base.hpp
@@ -74,10 +74,6 @@ namespace pybind11
         template <class Type>
         struct xtensor_type_caster_base
         {
-            bool load(handle /*src*/, bool)
-            {
-                return false;
-            }
 
         private:
 
@@ -106,6 +102,26 @@ namespace pybind11
 
         public:
 
+            bool load(handle src, bool convert)
+            {
+                using T = typename Type::value_type;
+
+                if (!convert && !array_t<T>::check_(src)) {
+                    return false;
+                }
+
+                auto buf = array_t<T, array::c_style | array::forcecast>::ensure(src);
+
+                if (!buf) {
+                    return false;
+                }
+
+                type_caster<Type>::value = Type::from_shape(buf.shape());
+                std::copy(buf.data(), buf.data() + buf.size(), type_caster<Type>::value.begin());
+
+                return true;
+            }
+
             // Normal returned non-reference, non-const value:
             static handle cast(Type&& src, return_value_policy /* policy */, handle parent)
             {