pertaining to C++11, whats wrong with my simple program?

Question

my name is Adam, I have just begun to learn C++, I love it, but am only on pg 181 in the seventh edition of sams teach yourself C++ in one hour a day, and pg 102 in the seventh edition of C++ for dummies. I have seven multi page notes on the sams book, and twenty one multi page notes on the for dummies book. Please help me understand why I get 5 errors with my simple program which will be shown shortly. I do not want to use -fpermissive option, I need to learn how to code correctly as I am not very experienced. Thank you everyone, very very much, I absolutely love C++, and even have a very good idea on a simple program I plan to learn how to write, which could allow program development time, or writing time to be reduced by 5-20 times on average. The following program shown is not this program however, but please help me so I may one day write, and use my program idea for a college paper. Thank you again, problem program follows:

            #include <iostream>
            using namespace std;

        int main()
    {
        cout<< "how many integers do you wish to enter? ";
        int InputNums = 0;
        cin>> InputNums;

        int* pNumbers = new int [InputNums];
        int* pCopy = pNumbers;

        cout<< "successfully allocated memory for "<<
         InputNums<< " integers"<<endl;
        for(int Index = 0; Index < InputNums; ++Index)
        {
            cout<< "enter number "<< Index << ": ";
            cin>> *(pNumbers + Index);
        }

            cout<< "displaying all numbers input: " <<endl;
        for(int Index = 0, int* pCopy = pNumbers;
                Index < InputNums; ++Index)
             cout<< *(pCopy++) << " ";

             cout<< endl;

             delete[] pNumbers;
             cout<< "press enter to continue..." << endl;
             cin.ignore(10, '\n');
             cin.get();

             return 0;
    }

The problem is indicated as being in the multiple initializations of the second for loop. Please tell me why my problem program will not compile. Thank you all. Sincerely Adam.

`for(int Index = 0, *pCopy = pNumbers; ...` . That'll get you past compiler errors. — Igor Tandetnik, Dec 20 '15 at 18:38
This is newmanadam speaking, I am extremely grateful for all of your input and help. Good work Igor Tandetnik 4, very quick response, and concise solution. Now, it is my belief that my book-s are attempting to illustrate basic principles, and may be starting with a few obsolete techniques in order to demonstrate others. Thank you all very much. — newmanadam, Dec 20 '15 at 23:52
o, I apologize Igor Tandetnik for adding a 4 after your name, I can see now that this 4 indicated 4 hours ago. I am admittedly a little drunk. Sorry — newmanadam, Dec 20 '15 at 23:58

score 2 · Answer 1 · edited May 23 '17 at 12:23

My first advice would be to find a better book.

Once you've done that, forget everything you think you know about using new to allocate an array (e.g., int* pNumbers = new int [InputNums];). It's an obsolete construct that you shouldn't use (ever).

If I had to write a program doing what you've outlined above, the core of it would look something like this:

cout<< "how many integers do you wish to enter? ";
int InputNums;
cin>> InputNums;

std::vector<int> numbers;

int temp;
for (int i=0; i<InputNums; i++) {
    cin >> temp;
    numbers.push_back(temp);
}

cout<< "displaying all numbers input:\n";

for (auto i : numbers)
    cout << i << " ";

score -2 · Answer 2 · answered Dec 20 '15 at 19:49

Directly answer your question: you cannot initialize variables of different types in the same for loop declaration.

In your example:

for(int Index = 0, int* pCopy = pNumbers;

int and int * are different types. Even if you use auto to let the compiler automatically deduct the types, both variables cannot have different deducted types.

The solution:

int Index = 0;
for(int *pCopy=pNumbers; ...

Having this one single secondary effect: Index is now not only confined to the scope of the for. Should this be a problem, you may do:

{
    int Index = 0;
    for(int *pCopy=pNumbers; ...
    ...
}

And now the scope of Index is limited to the surrounding curly braces.

`you cannot initialize variables of different types in the same for loop declaration` False. `for(int Index = 0, *pCopy = pNumbers;...)` works, and declares `Index` of type `int` and `pCopy` of type `int*`. — Igor Tandetnik, Dec 20 '15 at 19:59

pertaining to C++11, whats wrong with my simple program?

2 Answers2