Fix readme example and add test

Author: SylvainCorlay

README.md

@@ -100,17 +100,17 @@ import numpy as np
 import xtensor_python_test as xt
 
 x = np.arange(15).reshape(3, 5)
-y = [1, 2, 3]
+y = [1, 2, 3, 4, 5]
 z = xt.vectorized_func(x, y)
 z
 ```
 
 **Outputs**
 
 ```
-[[-1.      ,  0.301169,  1.325444,  1.131113, -0.103159],
- [-1.958924, -0.819718,  1.073133,  1.979351,  1.065762],
- [-1.544021, -1.540293, -0.120426,  1.41016 ,  1.644251]]
+[[-0.540302,  1.257618,  1.89929 ,  0.794764, -1.040465],
+ [-1.499227,  0.136731,  1.646979,  1.643002,  0.128456],
+ [-1.084323, -0.583843,  0.45342 ,  1.073811,  0.706945]]
 ``` 
 
 ## Installation

test/main.cpp

@@ -28,6 +28,11 @@ double readme_example1(xt::pyarray<double> &m)
     return std::accumulate(sines.begin(), sines.end(), 0.0);
 }
 
+double readme_example2(double i, double j)
+{
+    return std::sin(i) -  std::cos(j);
+}
+
 // Vectorize Examples
 
 int add(int i, int j)
@@ -43,6 +48,7 @@ PYBIND11_PLUGIN(xtensor_python_test)
     m.def("example2", example2, "");
 
     m.def("readme_example1", readme_example1, "");
+    m.def("readme_example2", xt::pyvectorize(readme_example2), "");
 
     m.def("vectorize_example1", xt::pyvectorize(add), "");
 

test/test_pyarray.py

@@ -35,3 +35,13 @@ def test_readme_example1(self):
         v = np.arange(15).reshape(3, 5)
         y = xt.readme_example1(v)
         np.testing.assert_allclose(y, 1.2853996391883833, 1e-12)
+
+    def test_readme_example2(self):
+        x = np.arange(15).reshape(3, 5)
+        y = [1, 2, 3, 4, 5]
+        z = xt.readme_example2(x, y)
+        np.testing.assert_allclose(z, 
+            [[-0.540302,  1.257618,  1.89929 ,  0.794764, -1.040465],
+             [-1.499227,  0.136731,  1.646979,  1.643002,  0.128456],
+             [-1.084323, -0.583843,  0.45342 ,  1.073811,  0.706945]], 1e-5)
+