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POWhy is this class abstract?
 

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    <p>I'm trying to create an implementation of a LinkedList that represents polynomials. The Linked list is going to be a list of "Term"s. A term is an implementation of Data (which is an abstract class with methods: compareTo() and toString()). The Polynomial class has a variable called head which I am trying to initialize as a Term. My compiler is saying that I "cannot declare member of abstract type: Term", but I did not think Term was abstract because it is an implementation of Data (the abstract class). If you guys could take a look at this and let me know of any huge red flags I'm missing, I would greatly appreciate it. Collection.h:</p> <pre><code> class Data { public: virtual ~Data() {} virtual int compareTo(Data * other) const = 0; virtual string toString() const = 0; }; class Term : public Data { public: int coefficient; string variable1; int exponentX; string variable2; int exponentY; Term * next; Term(int coeff, string var1, int exp1, string var2, int exp2, Term * next) : coefficient(coeff), variable1(var1), exponentX(exp1), variable2(var2), exponentY(exp2), next(next) {}; string convertInt(int number) { stringstream ss;//create a stringstream ss &lt;&lt; number;//add number to the stream return ss.str();//return a string with the contents of the stream } int compareTo(Term * term) { if(this-&gt;exponentX &gt; term-&gt;exponentX) { return 1; } else if(this-&gt;exponentX &lt; term-&gt;exponentX) { return -1; } else { if(this-&gt;exponentY &gt; term-&gt;exponentY) { return 1; } else if(this-&gt;exponentY &lt; term-&gt;exponentY) { return - 1; } else { return 0; } } } string toString() { stringstream s; int * current = &amp;this-&gt;coefficient; if(*current == 1 || *current == -1) { } else if(coefficient != 0) { s &lt;&lt; convertInt(coefficient); } else { return s.str(); } if(variable1 != "" &amp;&amp; this-&gt;exponentX != 0) { s &lt;&lt; variable1; s &lt;&lt; convertInt(exponentX); } if(variable2 != "" &amp;&amp; this-&gt;exponentY != 0) { s &lt;&lt; variable2; s &lt;&lt; convertInt(exponentY); } return s.str(); } }; </code></pre> <p>Also, here is implementation of LinkedList. There are some other methods in there, but they don't seem to be giving any issues.</p> <p>LinkedList.cpp:</p> <pre><code> class Polynomial : public LinkedList { public: Term head; Polynomial() { this-&gt;head = NULL; } ~Polynomial() { Term * current = head; while (current != NULL) { Term * next = current-&gt;next; delete current; current = next; } } </code></pre> <p>Thank you!</p>
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