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POBasic polynomial reading using linked lists
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  1. POBasic polynomial reading using linked lists
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    copied!<p>Ok, after failing to read a polynomial, I'm trying first a basic approach to this.</p> <p>So i have class polinom with function read and print:</p> <pre><code>#ifndef _polinom_h #define _polinom_h #include &lt;iostream&gt; #include &lt;list&gt; #include &lt;cstdlib&gt; #include &lt;conio.h&gt; using namespace std; class polinom { class term { public: double coef; int pow; term(){ coef = 0; pow = 0; } }; list&lt;term&gt; poly; list&lt;term&gt;::iterator i; public: void read(int id) { term t; double coef = 1; int pow = 0; int nr_term = 1; cout &lt;&lt; "P" &lt;&lt; id &lt;&lt; ":\n"; while (coef != 0) { cout &lt;&lt; "Term" &lt;&lt; nr_term &lt;&lt; ": "; cout &lt;&lt; "coef = "; cin &gt;&gt; coef; if (coef == 0) break; cout &lt;&lt; " grade = "; cin &gt;&gt; pow; t.coef = coef; t.pow = pow; if (t.coef != 0) poly.push_back(t); nr_term++; } } void print(char var) { for (i=poly.begin() ; i != poly.end(); i++ ) { //going through the entire list to retrieve the terms and print them if (poly.size() &lt; 2) { if (i-&gt;pow == 0) //if the last term's power is 0 we print only it's coefficient cout &lt;&lt; i-&gt;coef; else if (i-&gt;pow == 1) { if (i-&gt;coef == 1) cout &lt;&lt; var; else if (i-&gt;coef == -1) cout &lt;&lt; "-" &lt;&lt; var; else cout &lt;&lt; i-&gt;coef &lt;&lt; var; } else cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; "^" &lt;&lt; i-&gt;pow; //otherwise we print both } else { if (i == poly.end()) { // if we reached the last term if (i-&gt;pow == 0) //if the last term's power is 0 we print only it's coefficient cout &lt;&lt; i-&gt;coef; else if (i-&gt;pow == 1) cout &lt;&lt; i-&gt;coef &lt;&lt; var; else cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; "^" &lt;&lt; i-&gt;pow; //otherwise we print both } else { if (i-&gt;coef &gt; 0) { if (i-&gt;pow == 1)//if the coef value is positive cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; " + "; //we also add the '+' sign else cout &lt;&lt; cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; "^" &lt;&lt; i-&gt;pow &lt;&lt; " + "; } else { if (i-&gt;pow == 1)//if the coef value is positive cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; " + "; //we also add the '+' sign else cout &lt;&lt; cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; "^" &lt;&lt; i-&gt;pow &lt;&lt; " + "; } } } } } }; #endif </code></pre> <p>Well, it works when reading only one term but when reading more the printed coefficients are some random values and also after the last term it print '+' or '-' when it shouldn't.</p> <p>So any idea what's wrong?</p> <p>Thanks!</p> <p><strong>FINAL UPDATE</strong></p> <p>Ok, i made it work perfectly by modifying Bill's code so thanks a lot Bill and everyone else who commented or answered!</p> <p>Here's the final print function:</p> <pre><code> void print(char var) { list&lt;term&gt;::iterator endCheckIter; for (i=poly.begin() ; i != poly.end(); i++ ) { //going through the entire list to retrieve the terms and print them endCheckIter = i; ++endCheckIter; if (i-&gt;pow == 0) cout &lt;&lt; i-&gt;coef; else if (i-&gt;pow == 1) cout &lt;&lt; i-&gt;coef &lt;&lt; var; else cout &lt;&lt; i-&gt;coef &lt;&lt; var &lt;&lt; "^" &lt;&lt; i-&gt;pow; if (endCheckIter != poly.end()) { if (endCheckIter-&gt;coef &gt; 0) cout &lt;&lt; " + "; else { cout &lt;&lt; " - "; endCheckIter-&gt;coef *= -1; } } } </code></pre> <p>} </p>
 

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