Databases
StackOverflow2013
Postsdbo
POChoosing the data type for a generalized template class in main()
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POChoosing the data type for a generalized template class in main()
    primarykey
    data
    text
    <p>So I was asked to write a simple vector template and I believe I have written the class correctly, looking at some examples of generalized lists in our textbook (Savitch). Now I am trying to invoke the class in <code>main()</code> by letting the user choose the data type. I am running into problems after I declare the identifier <code>list1</code>. I want to be able to use the same identifier after using an if statement to switch the data type. However, I don't think the syntax in the body of my if statements is correct, since <code>list1</code> is already declared. In java I always thought after a class was declared you could call its construtor at any time, but I have no idea how to do that in C++. </p> <pre><code>#include &lt;iostream&gt; using namespace std; template &lt;class T&gt; class SimpleVector { public: SimpleVector(); SimpleVector(int); SimpleVector(const SimpleVector &amp; copy); ~SimpleVector(); int size(); T getElementAt(int n); T &amp; operator[](int index); private: T * item; int length; }; int main() { int dType; int dataSize; cout &lt;&lt; "What type of data do you want to enter?\n(1 for integer, 2 for double and 3 for strings)" &lt;&lt; endl; cin &gt;&gt; dType; cout &lt;&lt; "How many data inputs? " &lt;&lt; endl; cin &gt;&gt; dataSize; SimpleVector &lt;int&gt; list1; // if I dont declare then for loop doesn't recognize list as a declared variable. if (dType == 0) { SimpleVector &lt;int&gt; list1(dataSize); } else if (dType == 1) { SimpleVector &lt;double&gt; list1(dataSize); } else { SimpleVector &lt;string&gt; list1(dataSize); } cout &lt;&lt; "Please enter the data:" &lt;&lt; endl; for (int i = 0; i &lt; dataSize; i++) { cin &gt;&gt; list1[i]; } return 0; } template &lt;class T&gt; SimpleVector&lt;T&gt;::SimpleVector() { item = NULL; length = 0; } template &lt;class T&gt; SimpleVector&lt;T&gt;::SimpleVector(int s) { length = s; item = new T[length]; } template &lt;class T&gt; SimpleVector&lt;T&gt;::SimpleVector(const SimpleVector &amp; copy) { int newSize = copy - &gt; size(); item = new T[newSize]; for (int i = 0; i &lt; newSize; i++) item[i] = copy.item[i]; } template &lt;class T&gt; SimpleVector&lt;T&gt;::~SimpleVector() { delete[] item; } template &lt;class T&gt; int SimpleVector&lt;T&gt;::size() { return length; } template &lt;class T&gt; T SimpleVector&lt;T&gt;::getElementAt(int n) { return *(item + n); } template &lt;class T&gt; T &amp; SimpleVector&lt;T&gt;::operator[](int index) { return this-&gt;item[index]; } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USNatan
    1. USuser1871426
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POChoosing the data type for a generalized template class in main()
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POChoosing the data type for a generalized template class in main()
      1. This table or related slice is empty.
      1. VTApproveEditSuggestion
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload