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POAny suggestion for doing an arbitrary operation using given arguments of arbitrary types?
 

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  1. POAny suggestion for doing an arbitrary operation using given arguments of arbitrary types?
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    <p>Basically i just want to do an arbitrary operation using given arguments of arbitrary types.</p> <p>Argument type base class is Var, and Operation is base class of the operation that will executed for given arguments.</p> <p>I have Evaluator class, that hold a collection of operators which mapped using opId. Evaluator will do operation based on opId argument given in evaluate() member function, then evaluate() function will do search for supported operator that will accept argument type and opId.</p> <p>what I want to ask is, is there any <strong>efficient pattern or algorithm</strong> that will do this <strong>without dynamic_cast&lt;> and/or looping through operator collection</strong>.</p> <p>` </p> <pre><code>class Var { public: bool isValidVar(); static Var invalidVar(); } template&lt;typename T&gt; class VarT : public Var { public: virtual const T getValue() const; } class Operator { public: virtual Var evaluate(const Var&amp; a, const Var&amp; b) = 0; } template&lt;typename T&gt; class AddOperator : public Operator { public: virtual Var evaluate(const Var&amp; a, const Var&amp; b) { //dynamic_cast is slow! const VarT&lt;T&gt;* varA = dynamic_cast&lt;const VarT&lt;T&gt;*&gt;(&amp;a); const VarT&lt;T&gt;* varB = dynamic_cast&lt;const VarT&lt;T&gt;*&gt;(&amp;b); if(varA &amp;&amp; varB) //operation supported { return VarT&lt;T&gt;(varA-&gt;getValue() + varA-&gt;getValue()); } return Var::invalidVar(); //operation for this type is not supported } } class Evaluator { private: std::map&lt;int,std::vector&lt;Operator&gt;&gt; operatorMap; public: virtual Var evaluate(const Var&amp; a, const Var&amp; b,int opId) { std::map&lt;int,std::vector&lt;Operator&gt;&gt;::iterator it = this-&gt;operatorMap.find(opId); if(it != this-&gt;operatorMap.end()) { for(size_t i=0 ; i&lt;it-&gt;second.size() ; i++) { Var result = it-&gt;second.at(i).evaluate(a,b); if(result.isValidVar()) { return result; } } } //no operator mapped, or no operator support the type return Var::invalidVar(); } } </code></pre> <p>`</p>
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    1. USVinko Vrsalovic
    1. USuray
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      1. POAny suggestion for doing an arbitrary operation using given arguments of arbitrary types?
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    1. COPlease clarify, it appears you have several collections of operations. Your OpId corresponds to more than one operation. What is the criterion for which operation you want to use?
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      1. POAny suggestion for doing an arbitrary operation using given arguments of arbitrary types?
      1. USBjörn Pollex
    2. COyes for each opId it could have more than one operator, the operator to use is the operator which could accept the Type of the given arguments. for example i have AddOperator<int>, AddOperator<float>, AddOperator<Matrix>, AddOperator<Vec>, all of those operators are mapped to one opId (which is id for addition) but have different Operator for each argument type
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      1. POAny suggestion for doing an arbitrary operation using given arguments of arbitrary types?
      1. USuray
    3. COHow would you not loop when using a container of operations? Is implicit looping with BOOST_FOREACH enough?
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      1. USstefaanv
 

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