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PORelational Operator Implementation Dilemma
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  1. PORelational Operator Implementation Dilemma
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    copied!<p>I'm in the process of designing several classes that need to support operators <code>!=</code>, <code>&gt;</code>, <code>&lt;=</code>, and <code>&gt;=</code>. These operators will be implemented in terms of operators <code>==</code> and <code>&lt;</code>.</p> <p>At this stage, I need to make a choice between inheritance¹ and forcing my consumers to use <code>std::rel_ops</code>² "manually".</p> <p>[1] Inheritance (possible implementation):</p> <pre><code>template&lt;class T&gt; class RelationalOperatorsImpl { protected: RelationalOperatorsImpl() {} ~RelationalOperatorsImpl() {} friend bool operator!=(const T&amp; lhs, const T&amp; rhs) {return !(lhs == rhs);} friend bool operator&gt;(const T&amp; lhs, const T&amp; rhs) {return (rhs &lt; lhs);} friend bool operator&lt;=(const T&amp; lhs, const T&amp; rhs) {return !(rhs &lt; lhs);} friend bool operator&gt;=(const T&amp; lhs, const T&amp; rhs) {return !(lhs &lt; rhs);} }; template&lt;typename T&gt; class Foo : RelationalOperatorsImpl&lt; Foo&lt;T&gt; &gt; { public: explicit Foo(const T&amp; value) : m_Value(value) {} friend bool operator==(const Foo&amp; lhs, const Foo&amp; rhs) {return (lhs.m_Value == rhs.m_Value);} friend bool operator&lt;(const Foo&amp; lhs, const Foo&amp; rhs) {return (lhs.m_Value &lt; rhs.m_Value);} private: T m_Value; }; </code></pre> <p>[2] <code>std::rel_ops</code> glue:</p> <pre><code>template&lt;typename T&gt; class Foo { public: explicit Foo(const T&amp; value) : m_Value(value) {} friend bool operator==(const Foo&amp; lhs, const Foo&amp; rhs) {return (lhs.m_Value == rhs.m_Value);} friend bool operator&lt;(const Foo&amp; lhs, const Foo&amp; rhs) {return (lhs.m_Value &lt; rhs.m_Value);} private: T m_Value; }; void Consumer() { using namespace std::rel_ops; //Operators !=, &gt;, &gt;=, and &lt;= will be instantiated for Foo&lt;T&gt; (in this case) on demand. } </code></pre> <p>I'm basically trying to avoid code repetition. Any thoughts as to which method "feels" better?</p>
 

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