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POHow do I access the member variables in the STL string class?
 

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  1. POHow do I access the member variables in the STL string class?
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    <p>I'm working on one of the programming challenges in the book Starting Out With C++ Early Objects 7th Edition and one of the assignments asks to create a class which is derived from the STL string class. I'm posting the question for the purpose of understanding what I am allowed to do and how I am supposed to implement the solution so that no one offers more advanced suggestions.</p> <p>-- Question as it is written in the text --</p> <p>Palindrome Testing</p> <p>A Palindrome is a string that reads the same backward as forward. For example, the words mom, <em>dad</em>, <em>madam</em>, and <em>radar</em> are palindromes. Write a <code>class Pstring</code> that is derived from the <code>STL string class</code>. The <code>Pstring class</code> adds a member function</p> <pre><code>bool isPalindrome() </code></pre> <p>that determines whether the string is a palindrome. Include a constructor that takes an <code>STL string</code> object as a parameter and passes it to the string base class constructor. Test your class by having a main program that asks the user to enter a string. The program uses the string to initialize a Pstring object and then calls isPalindrome() to determine whether the string entered is a palindrome.</p> <p>You may find it useful to use the subscript operator [] of the string class: if str is a string object and k is an integer, then str[k] returns the caracter at the position k in the string.</p> <p>-- End --</p> <p>My main question is how do I access the member variable which holds my string object if the class I am deriving Pstring from is a class I did not write and I do not know how it implements its members?</p> <p>For example,</p> <pre><code>#include &lt;string&gt; using namespace std; class Pstring : public string { public: Pstring(std::string text) : string(text) { } bool isPalindrome() { // How do I access the string if I am passing it to the base class? // What I think I should do is... bool is_palindrome = true; auto iBegin = begin(); auto iEnd = end() - 1; while (iBegin &lt; iEnd &amp;&amp; is_palindrome) { if (*iBegin++ != *iEnd--) is_palindrome = false; } return is_palindrome; // But I think this is wrong because... // #1 The book did not discuss the keyword auto yet // #2 The book discussed when a class is derived from another class, // how the members from super class will be accessible to the sub class. // However, with this assignment, I don't see how to access the members. } } </code></pre> <p>The reason I feel like I am doing this incorrectly is because the assignment mentions using subscript notation, however, I don't understand how to use the subscript notation if I don't know the name of the variable where the string is stored.</p> <p>Any help would be greatly appreciated because the author does not provide the solutions unless I am an instructor which is pretty lame in my opinion. It probably has to do with the fact that this is an academic text.</p>
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    1. USBill the Lizard
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    1. CONever derive from stl classes. Always a bad idea. Why don't you try composition instead?
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    2. COThe author may not provide solutions because he is an idiot.
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    3. CO@Ethan Steinberg I completely agree, however, this assignment specifically asks to do that.
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