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POHow do I make my matrix object implicitly convert to scalar when its dimensions are 1x1?
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  1. POHow do I make my matrix object implicitly convert to scalar when its dimensions are 1x1?
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    copied!<p>I have written a <code>Matrix</code> class. It does multiplications between matrices. Sometimes multiplication of matrices yield a 1x1 matrix (e.g.; inner product of two column vectors). Is it possible to make a <code>Matrix</code> object directly return a scalar value when it is one-by-one?</p> <pre><code>template &lt;class T&gt; class Matrix { public: // ... T&amp; operator()(uint64_t unRow, uint64_t unCol = 0) throw(MatrixOutOfRange); const T&amp; operator()(uint64_t unRow, uint64_t unCol = 0) const throw(MatrixOutOfRange); // ... protected: std::vector&lt;T&gt; MatrixArray; // ... }; // ... template &lt;class T&gt; T &amp; Matrix&lt;T&gt;::operator()(uint64_t unRow, uint64_t unCol /*= 0*/) throw(MatrixOutOfRange) { /* Bound checking here */ return MatrixArray[m_unColSize * unRow + unCol]; } template &lt;class T&gt; const T &amp; Matrix&lt;T&gt;::operator()(uint64_t unRow, uint64_t unCol /*= 0*/) const throw(MatrixOutOfRange) { /* Bound checking here */ return MatrixArray[m_unColSize * unRow + unCol]; } // ... </code></pre> <hr> <p>Example code:</p> <p><img src="https://i.stack.imgur.com/ziirN.png" alt="Latex image"></p> <pre><code>Matrix&lt;double&gt; A (3, 1, 1.0, 2.0, 3.0); Matrix&lt;double&gt; AT(1, 3, 1.0, 2.0, 3.0); // Transpose of the A matrix Matrix&lt;double&gt; B (3, 1, 4.0, 5.0, 6.0); Matrix&lt;double&gt; C(); C = AT * B; double Result1 = C(0, 0); double Result2 = (AT * B)(0, 0); double Result3 = A.InnerProductWith(B)(0, 0); </code></pre> <p>I want to drop the unnecessary element location specifier arguments <code>(0, 0)</code> when the result is a one-by-one matrix. Like this:</p> <pre><code>C = AT * B; double Result1 = C; double Result2 = AT * B; double Result3 = A.InnerProductWith(B); </code></pre> <p>It is OK if it throws an exception if the result is not one-by-one.</p>
 

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