C++ Calling Template Function Error

Question

When trying to compile the following code:

int main(){

    Array<int> *testArray = new Array<int>(5);
    testArray->initArray<int>(testArray);
    testArray->printArray<int>(testArray);



    return 0;
}

Using this template:

template<typename T>
class Array{
public:
    Array(int size){
        size = size;
        data = new T[size];
    };
    Array<T> addData(T dataToAdd){
        Array <T> *tmp = new Array <T> (this->size);
        tmp = this->data;
        Array <T> *newData = new Array<T> (this->size + 1);

        for (int i = 0; i < this->size + 1; ++i){
            if (i < this->size){
                newData->data[i] = tmp[i];
            }
            else{
                newData->data[i] = dataToAdd;
            }
        }
        return newData;
    };
    void initArray(T arrayToInit){
        for (int i = 0; i < this->size; ++i){
            this->data[i] = i;
        }
    };
    void printArray(T arrayToPrint){
        ostringstream oss;
        string answer = "";

        for (int i = 0; i < arrayToPrint->size; ++i){
            oss << arrayToPrint[i] + " ";
        }

        answer = oss.str();

        cout << answer << endl;
    };

private:
    int size;
    T* data;
};

I get the following error in my int main() :

"expected primary-expression before ‘int’"

for both of my function calls (initArray and printArray). I am fairly new to C++ and have little experience with templates in particular, any advice would be greatly appreciated. Thank you for your time.

EDIT: Thank you everyone for the responses and constructive criticism, I have made a great amount of progress thanks to everybody's help.

`initArray()` should be `initArray()` but that's just the start of your problems. — Captain Obvlious, Oct 01 '15 at 03:32
The parameters to `initArray` and `printArray` have no use. They should be removed. — owacoder, Oct 01 '15 at 03:33
Thank you for your feedback so far, any other issues you see that you can point out would be very helpful, thank you! — Biggytiny, Oct 01 '15 at 03:34

MikeCAT · Answer 1 · 2015-10-01T03:39:11.100

You don't need <int> to call the function in this case. (Thinking about std::vector<int>, you will write hoge.push_back(0) instead of hoge.push_back<int>(0).)

The arguments of Array::initArray and Array:;:printArray are also invalid and unneeded.

Fixed code (emits no compile errors/warnings, but not working properly):

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

template<typename T>
class Array{
public:
    Array(int size){
        size = size;
        data = new T[size];
    };
    Array<T> addData(T dataToAdd){
        Array <T> *tmp = new Array <T> (this->size);
        tmp = this->data;
        Array <T> *newData = new Array<T> (this->size + 1);

        for (int i = 0; i < this->size + 1; ++i){
            if (i < this->size){
                newData->data[i] = tmp[i];
            }
            else{
                newData->data[i] = dataToAdd;
            }
        }
        return newData;
    };
    void initArray(){
        for (int i = 0; i < this->size; ++i){
            this->data[i] = i;
        }
    };
    void printArray(){
        ostringstream oss;
        string answer = "";

        for (int i = 0; i < this->size; ++i){
            oss << data[i] + " ";
        }

        answer = oss.str();

        cout << answer << endl;
    };

private:
    int size;
    T* data;
};

int main(){

    Array<int> *testArray = new Array<int>(5);
    testArray->initArray();
    testArray->printArray();



    return 0;
}

If you're going to provide additional improvements you might as well dump the two-phase initialization move that logic into the constructor. — Captain Obvlious, Oct 01 '15 at 03:39
I am stunned that `size = size;` and `tmp = this->data;` produce no warnings or errors. — user4581301, Oct 03 '15 at 00:34

basav · Answer 2 · 2015-10-01T03:54:24.293

Here is the changed working code:

#include <string>
#include <iostream>
#include <cstdint>
#include <iostream>
#include <string>
#include <sstream>


using namespace std;

template<typename T>
class Array{
public:
    Array(int size){
        size = size;
        data = new T[size];
    }
    Array<T> addData(T dataToAdd){
        Array <T> *tmp = new Array <T> (this->size);
        tmp = this->data;
        Array <T> *newData = new Array<T> (this->size + 1);

        for (int i = 0; i < this->size + 1; ++i){
            if (i < this->size){
                newData->data[i] = tmp[i];
            }
            else{
                newData->data[i] = dataToAdd;
            }
        }
        return newData;
    }
    void initArray(Array<T>* arrayToInit){
        for (int i = 0; i < this->size; ++i){
            this->data[i] = i;
        }
    }
    void printArray(Array<T>* arrayToPrint){
        ostringstream oss;
        string answer = "";

        //for (int i = 0; i < arrayToPrint->size; ++i){
           // oss << data[i] + " ";
             answer = oss.str();

        cout << answer << endl;
    }

private:
    int size;
    T* data;
};



int main()
{
   string s;
   double d =9.0;

   s=d;

    Array<int> *testArray = new Array<int>(5);
    testArray->initArray(testArray);
    testArray->printArray(testArray);
   return 0;
}

Changes carried out:

Template Instantiation happens when you declare the class.No need to again do it for its member functions.

Also no need to append ; after every member function definition, only needed for class definition.

C++ Calling Template Function Error

2 Answers2

Linked