Added inplace operations exercise

Author: rougier

README.html

@@ -238,6 +238,17 @@ <h2 class="subtitle" id="a-joint-effort-of-the-numpy-community">A joint effort o
 <span class="name">np</span><span class="operator">.</span><span class="name">sqrt</span><span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">)</span> <span class="operator">==</span> <span class="name">np</span><span class="operator">.</span><span class="name">emath</span><span class="operator">.</span><span class="name">sqrt</span><span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">)</span>
 </pre>
 </li>
+<li><p class="first">How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)</p>
+<pre class="code python literal-block">
+<span class="name">A</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">)</span><span class="operator">*</span><span class="literal number integer">1</span>
+<span class="name">B</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">)</span><span class="operator">*</span><span class="literal number integer">2</span>
+<span class="name">C</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">)</span><span class="operator">*</span><span class="literal number integer">3</span>
+<span class="name">np</span><span class="operator">.</span><span class="name">add</span><span class="punctuation">(</span><span class="name">A</span><span class="punctuation">,</span><span class="name">B</span><span class="punctuation">,</span><span class="name">out</span><span class="operator">=</span><span class="name">B</span><span class="punctuation">)</span>
+<span class="name">np</span><span class="operator">.</span><span class="name">divide</span><span class="punctuation">(</span><span class="name">A</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">,</span><span class="name">out</span><span class="operator">=</span><span class="name">A</span><span class="punctuation">)</span>
+<span class="name">np</span><span class="operator">.</span><span class="name">negative</span><span class="punctuation">(</span><span class="name">A</span><span class="punctuation">,</span><span class="name">out</span><span class="operator">=</span><span class="name">A</span><span class="punctuation">)</span>
+<span class="name">np</span><span class="operator">.</span><span class="name">multiply</span><span class="punctuation">(</span><span class="name">A</span><span class="punctuation">,</span><span class="name">B</span><span class="punctuation">,</span><span class="name">out</span><span class="operator">=</span><span class="name">A</span><span class="punctuation">)</span>
+</pre>
+</li>
 <li><p class="first">Extract the integer part of a random array using 5 different methods (★★☆)</p>
 <pre class="code python literal-block">
 <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">)</span>

README.rst

@@ -284,6 +284,18 @@ Thanks to Michiaki Ariga, there is now a
 
       np.sqrt(-1) == np.emath.sqrt(-1)
 
+#. How to compute ((A+B)*(-A/2)) in place (without copy)? (★★☆)
+
+   .. code-block:: python
+
+      A = np.ones(3)*1
+      B = np.ones(3)*2
+      C = np.ones(3)*3
+      np.add(A,B,out=B)
+      np.divide(A,2,out=A)
+      np.negative(A,out=A)
+      np.multiply(A,B,out=A)
+      
 #. Extract the integer part of a random array using 5 different methods (★★☆)
 
    .. code-block:: python