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    <ol> <li><p>The method you declared is not <code>const</code>. It returns a <code>const void</code> (whatever that is), but it is not a <code>const</code>-method itself.</p></li> <li><p>If it were declared</p> <pre><code>void modify(float&amp; dummy) const </code></pre> <p>it would be a const-method, but then still it could modify the value of the argument, because a const-method is allowed to do this. The only thing it is not allowed to do is to modify values of members of the class it belongs to.</p></li> <li><p>Note that in order to declare a <code>const</code> method, I had to remove the <code>static</code> specification. A <code>static</code> method can never be <code>const</code>, because a static method can't modify any members anyway.</p></li> <li><p>If you want to prevent the function from modifying its argument, you'd have to make the argument const:</p> <pre><code>static void modify(const float&amp; dummy) </code></pre></li> </ol> <hr> <p>To illustrate what a const-method can and cannot do, here is a class that has a member, and a const-function:</p> <pre><code>class A { float my_member; public: void modify(float&amp; dummy) const { my_member = dummy; // attempt to modify member -&gt; illegal dummy = 1.5f; // modifies a non-const argument -&gt; ok } }; </code></pre> <p>As you can see, it cannot modify a member, but it can modify the value of its argument. If you want to prevent that, you need to make the argument <code>const</code>:</p> <pre><code>class A { float my_member; public: void modify(const float&amp; dummy) const { my_member = dummy; // attempt to modify member -&gt; illegal dummy = 1.5f; // attempt to modify a const reference -&gt; illegal } }; </code></pre>
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    1. COso the point 4 is the only solution for this and all the void methods ?
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    2. CONo its to prevent argument modifying.
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    3. CO@user1802174, It's the only solution for every function. The return type has nothing to do with it.
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