title: Isn't "const" redundant when passing by value?
body: <p>I was reading my C++ book (Deitel) when I came across a function to calculate the volume of a cube. The code is the following:</p>
  
  <pre><code>double cube (const double side){
      return side * side * side;
  }
  </code></pre>
  
  <p>The explanation for using the "const" qualifier was this one: "The const qualified should be used to enforce the principle of least privilege, telling the compiler that the function does not modify variable side".</p>
  
  <p><strong>My question</strong>: isn't the use of "const" redundant/unnecessary here since the variable is being passed by value, so the function can't modify it anyway?</p>