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POHow to pass references by value in C++?
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copied!<p>I'm trying to create am immutable type (class) in C++,</p> <p>I made it so that all methods "aka member functions" don't modify the object and return a new instance instead.</p> <p>I'm running across a bunch of issues, but they all revolve around the reference types in C++.</p> <p>One example is when passing parameters of the same class type by reference:</p> <pre><code>Imm Imm::someOp( const Imm& p_im ) const { ... p_im = p_im.someOtherOp(); //error, p_im is const, can't modify it! ... } </code></pre> <p>The error is caused by passing the value by reference. If instead, I was passing the reference by value, then the error line above would not be an error! </p> <p>Consider a Java/C# example</p> <pre><code>class Imm { ... Imm someOp( Imm p_im ) { .... p_im = p_im.someOtherOp(); //ok, you're not modifying the //original object, just changing the local reference .... } .... } </code></pre> <p>How can I do something like this in C++? I know I can use pointers but then I run into the whole memory management mess. I don't want to worry about who owns references to objects. </p> <p>Ideally I'd like to design the class to be like immutable strings in python; you can use them without ever noticing or even knowing that they're immutable, and they just behave as you expect; they just work.</p> <p><strong>EDIT</strong></p> <p>Of course I can get around it by passing-by-value or by using a temp variable (which is what I'm doing currently). What I'm asking about is "how to pass references by value in C++"</p> <p>I'm expecting the answer to revolve around something in the STL, I'm currently looking into smart_ptr family of templates.</p> <p><strong>UPDATE</strong></p> <p>Thanks for the responses, I realize there's no escape from pointers. (see my <a href="https://stackoverflow.com/questions/653211/stl-class-for-reference-counted-pointers">other question</a>, which is really a follow up on this one)</p>

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