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POc++ Overload operator bool() gives an ambiguous overload error with operator+
 

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  1. POc++ Overload operator bool() gives an ambiguous overload error with operator+
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    <p>I'm compiling some c++ code of a class MegaInt which is a positive decimal type class that allows arithmetic operations on huge numbers.</p> <p>I want to overload operator bool to allow code like this:</p> <pre><code>MegaInt m(45646578676547676); if(m) cout &lt;&lt; "YaY!" &lt;&lt; endl; </code></pre> <p>This is what I did:</p> <p>header:</p> <pre><code>class MegaInt { public: ... operator bool() const; }; const MegaInt operator+(const MegaInt &amp; left, const MegaInt &amp; right); const MegaInt operator*(const MegaInt &amp; left, const MegaInt &amp; right); </code></pre> <p>implementation:</p> <pre><code>MegaInt::operator bool() const { return *this != 0; } const MegaInt operator+(const MegaInt &amp; left, const MegaInt &amp; right) { MegaInt ret = left; ret += right; return ret; } </code></pre> <p>Now, the problem is if I do:</p> <pre><code>MegaInt(3424324234234342) + 5; </code></pre> <p>It gives me this error:</p> <blockquote> <p>ambiguous overload for 'operator+' in 'operator+(const MegaInt&amp;, const MegaInt&amp;) note: candidates are: operator+(int, int) | note: const MegaInt operator+(const MegaInt&amp;, const MegaInt&amp;)|</p> </blockquote> <p>I don't know why. How is the overloaded bool() causing operator+ to become ambiguous?¸</p> <p>Thank You.</p> <hr> <p>Well, everyone gave me great answers, unfortunately, none of them seem to solve my problem entirely.</p> <p><strong>Both void* or the Safe Bool Idiom works.</strong> Except for one tiny problem, I hope has a workaround:</p> <p>When comparing with 0 like:</p> <pre><code>if (aMegaInt == 0) </code></pre> <p>The compiler gives an ambiguous overload error again. I understand why: it doesn't know if we're comparing to false or to MegaInt of value 0. None the less, in that case, I'd want it to cast to MegaInt(0). Is there a way to force this?</p> <p>Thank You Again.</p>
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    1. COMight need to use the [safe bool idiom](http://en.wikibooks.org/wiki/More_C%2B%2B_Idioms/Safe_bool).
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