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POC++ equivalent of Matlab Abstract for class properties
 

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  1. POC++ equivalent of Matlab Abstract for class properties
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    <p><strong>Short version:</strong><br> Consider the following pseudo-code:</p> <pre class="lang-cpp prettyprint-override"><code>class Foo { private: abstract type myVar; } // This class is abstract </code></pre> <p>How would you implement this behaviour in standard C++?</p> <hr> <p><strong>Long version:</strong><br> I have to port a lot of Obj-Oriented code from Matlab to C++. Note that I am the least experienced person in the world with Matlab and I do not use C++ since 2007.</p> <p>I googled a lot on this topic but i couldn't find a proper answer to my question. So here I am :)</p> <p>Let's say that you have this matlab class:</p> <pre class="lang-m prettyprint-override"><code>classdef Foo &lt; handle properties (Abstract, Dependent) A end properties B end methods (Abstract) computeA() end methods (Access = protected) function obj = Foo(bar) obj.B = Matlab.BlaBlaBla(bar) end end </code></pre> <p>This class (i suppose) cannot be allocated "directly" since it's constructor is protected. Also is property "A" is Abstract (ignore for a moment the fact that is also Dependent). MathWorks tells us that this means that:</p> <ul> <li>Concrete subclasses must redefine abstract properties without the Abstract attribute, and must use the same values for the SetAccess and GetAccess attributes as those used in the abstract superclass.</li> <li>Abstract properties cannot define set or get access methods (see Property Access Methods) and cannot specify initial values. The subclass that defines the concrete property can create set or get access methods and specify initial values.</li> </ul> <p>So how would you correctly translate such behaviour in C++? Would it be right if I do as follow? (By right I mean that it is not a bad design practice)</p> <pre class="lang-cpp prettyprint-override"><code>class Foo { private: type A; type B; protected: virtual void computeA() = 0; Foo(type bar) { this.B = SomeFoo(bar); } } </code></pre> <p>What I think (and I may be wrong) is that if I'm doing so one will have to do</p> <pre class="lang-cpp prettyprint-override"><code>class Subclass: Foo { protected: void computeA(){...} public: type A() { computeA(); return A; } //This is A getter that grants Dependent behavior } </code></pre> <p>Or otherwise get an error at compile time.</p> <p>Am i wrong? Is there a better way to do so? Also is the that right way to translate the Dependent keyword?</p>
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    1. COAt least based on your description, it sounds to me like Matlab properties are enough of a mess (read that as "foreign enough to C++", if you prefer) that *any* translation into C++ is going to do one of two things: either change the code a lot, or end up as fairly poor (or at least strange) C++.
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      1. USJerry Coffin
    2. COThe Abstract keyword definition has been taken from MathWorks website. Also I don't think that a behavior such the one obtained by using the Dependent keyword is such strange in C++. It grants you that the attribute A gets computed only if you need it and it grants you that it is always updated when you use it. Also put into account that i might have misunderstood what Dependent means for matlab :)
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    3. COnote that Subclass cannot access Foo's private member A.
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      1. USPhilipp
 

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