type declaration real time?

[dark ninjuh]

Hello. I am trying to make a simple program that asks for user input. then outputs it. But you don't know what type of value the user is going to input.
I thought this was what templates were for? I created a class like this

 template <class T>
class input{
private:
T value;

public:
    T makeinput(){

     std::cin >> value;
     return value;
     }
    void display(){
    std::cout << value;
    }
};

(im really new to templates) Then i did this in main and realised it still has to be declared before runtime

int main()
{
input < >one;// <--- still has to be declared?
one.makeinput();
one.display();

return 0;
}

how would you make it define that in realtime? like if the input is a string, its stored as a string. or is this not possible?

[MiiNiPaa]

like if the input is a string, its stored as a string. or is this not possible?

It is not possible. All (possible) types should be known in compile time. Even without that, compiler cannot read your mind.
Think logically: is input 123 is integer 123, double 123.0 or string "123"?

You can get your input as string, determine input type and create instance of needed type.

[dark ninjuh]

oh i didnt think of that.. Yeah that makes sense.

[Atyab]

You can make use of the templates when an operation is similar for different data types like adding, subtracting, multiplying and dividing two numbers as follows:

#include <iostream>
#include <string>

using namespace std;

template<class MT>
MT calculate_sum(MT num_a, MT num_b)
{
    return num_a+num_b;    
}

int main()
{
    int a = 5, b = 3;
    
    cout << calculate_sum(a, b);
    cout << endl;
    
    float c = 5.5, d = 5.0;
    
    cout << calculate_sum(c, d);
    cout << endl;
    
    return 0;
}

Use generic functions (templates) if Implementation of a function is same but the type of arguments may differ. In this way you don't need to overload functions with same number of parameters and implementation.