New int by user input - c++

Question

I have a problem. I want to create an integer by user input. For example:
#include <iostream>
#include <string>
using namespace std;
int main()
{
int i = 0;
char newVar;
string newVarName;
cout << "New Variable? (y/n)" << endl;
cin >> newVar;
if (newVar == 'y') {
/* newVarName declares new int with the name
of the user input (newVarName = test --> int test)*/
} else {
break;
}
return 0;
}
How can I do this?

Answer 1

As #Fantastic Mr Fox mentioned :
int name_dependant_on_user_input = value_from_user
This is impossible in c++, because the variable name, is a compile
time thing. The user input happens at runtime, which is after
compilation has completed. Something you could do, is map a string
input to your user input, for eg.
Some other error: String should be string or std::string. And using break; while not within loop or switch statements will return an error. If you want to escape immidiately, you could use exit(0);
Otherwise, as #Eljay mentioned above, a map<string, int> can be used to store both the name and value of your variable:
#include <iostream>
#include <string>
#include <map>
using namespace std;
int main()
{
char newVar;
string newVarName;
map<string, int> varName;
cout << "New Variable? (y/n) : ";
cin >> newVar;
if (newVar == 'y') {
cout << "Name : "; cin >> newVarName;
cout << "Int : "; cin >> varName[newVarName];
} else {
exit(0);
}
//testing
cout << "Test : " << newVarName << " = " << varName[newVarName];
return 0;
}
Result:
New Variable? (y/n) : y
Name : var
Int : 5
Test : var = 5
Also, see why using namespace std; is considered a bad practice.
More info:
std::map : https://en.cppreference.com/w/cpp/container/map
std::string: https://en.cppreference.com/w/cpp/string/basic_string

Answer 2

In c++, you need to be aware of the common concepts of compile time and run time. So in your example:
// newVarName declares new int with the name of the user input
If you mean something like this:
int name_dependant_on_user_input = value_from_user
This is impossible in c++, because the variable name, is a compile time thing. The user input happens at runtime, which is after compilation has completed. Something you could do, is map a string input to your user input, for eg.
std::unordered_map<std::string, int> user_vars;
std::string variable_name;
int variable_value;
cin >> variable_name;
cin >> variable_value;
user_vars[variable_name] = variable_value;
...
for (const auto& value_pair : user_Vars) {
std::cout << "User value for " << value_pair.first << " is " << value_pair.second;
}