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    <p>It's a tough concept to implement in C++, as you're seeing. I'm always a proponent of using the Boost library, which has <a href="http://www.boost.org/doc/libs/1_38_0/doc/html/variant.html" rel="nofollow noreferrer">already solved it for you</a>. You can typedef the complex boost variant template class to something more usable in your specific domain, so </p> <pre><code>typedef boost::variant&lt; int, float, bool &gt; ParamT; class Param { public: // initialize the variants Param(ParamT min, ParamT max, ParamT value) : m_Min(min), m_Max(max), m_Value(value) {} // example accessor template&lt;typename OutT&gt; const ParamT&amp; value() { return boost::get&lt;OutT&gt;(m_Value); } // other accessors for min, max ... private: ParamT m_Min, m_Value, m_Max; }; Param speed(-10.0f, 10.0f, 0.0f); float speedValue = speed.value&lt;float&gt;(); </code></pre> <p>Now, to add another type to your variant (eg, long, std::string, whatever) you can just modify the typedef of ParamT; The catch, here, is that the burden of checking the types is on you - it'll throw an exception if you store a float and try to receive an int, but there's no compile-time safety.</p> <p>If you want to get really crazy, you can implement an overloaded cast operator on a proxy object....</p> <pre><code>class ProxyValue { public: ProxyValue(ParamT&amp; value) : m_Value(value) {} template&lt;typename ValueT&gt; operator ValueT() { return boost::get&lt;ValueT&gt;(m_Value); } private: ParamT&amp; m_Value; }; </code></pre> <p>You'd return this from a non-templated value() function in Param, instead of the variant itself. Now you can assign a value without the template call..</p> <pre><code>Param speed(-10.0f, 0, 10); float speedValue = speed.value(); </code></pre> <p>Though fair warning, you're stepping into meta-programming hell here. Here thar be dragons. And as always, this is not a complete solution, just a pointer. YMMV.</p> <p><a href="http://codepad.org/QchqIhH6" rel="nofollow noreferrer">Heres a roughly working version showing how to use it, and the failures that are easy to hit.</a></p>
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    1. POcontainer of mixed types in C++ (similar to nsdictionary)
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    1. COwow this looks perfect thanks. Definitely no point re-inventing the wheel, i'll check out boost::variant.
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    2. COi've tried this and I'm really close, but there are a few minor annoyances - with both your code, and my slightly modded version without a proxy ( http://codepad.org/CUHHfYVi ). Your sample code works, but if I try: float a = speed.value() * 2.0f; it doesn't compile complaining that the * operator hasn't been overloaded. I have to write: float a = (float)speed.value() * 2.0f; And I get an assert when i write: int ispeed = (int)speed.value(); I have to do: int ispeed = (int)(float)speed.value(); are there any tricks to address these?
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    3. COFixing those issues will be more and more work, and make your code more dangerous the more magic you do. That said, the easiest way to deal with the first issue (operator * not defined) is to define it on your class and have it do the smart retrieval. The issue with casting to a different type (if you store a float but want to get it as an integer) is more difficult - basically the variant is throwing away the type information, so you need to specify it to retrieve it. Explicitly casting ( with (int)(float)speed.value() ) will probably save you from shooting yourself in the foot.
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