How to declare a variable using another variable?

Question

I'm trying to make a function in C++ that can make a new integer type variable according to the name that has been provided

for eg

void my_variable(char name)
{
    int "something here" = 1;  // i am figuring out what to write 
    // there so that it makes a variable from that character that i have sent

    cout << "something here";
}

Local variable names only exist at compile time, so such a feature would have no use. Perhaps you can explain your high-level goal? — cdhowie
– cdhowie, Commented Jun 11, 2012 at 20:48
preprocessor can do this with ## to join strings into whatever. — Michael Dorgan
– Michael Dorgan, Commented Jun 11, 2012 at 20:50
Maybe you like to define a class MyInt with a 'name' attribute in it? — hoffmaje
– hoffmaje, Commented Jun 11, 2012 at 20:50
well im sort of new to the language.. u know , still using the Borland Turbo C++.. I was kinda hoping that i could assign variables like these, in a game — Pulkit ShaRma
– Pulkit ShaRma, Commented Jun 11, 2012 at 20:53

learnvst · Accepted Answer · 2012-06-11 20:59:34Z

4

Look at using std::map. It allows you to create key-value pairs. The key would be name in this instance and the value would be the int. The following snippet shows you how to make a map, populate it, and then search for a value based on a key . . .

void my_function(std::string name)
{
    std::map<std::string, int> myMap;
    myMap[name] = 1;  // 

    cout << "Key " << name << " holds " << paramMap.find(name)->second << std::endl;
}

edited Jun 11, 2012 at 20:59

answered Jun 11, 2012 at 20:49

learnvst

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2 Comments

cdhowie Over a year ago

Well, std::pair allows you to create key-value pairs. std::map allows you to look up pairs by the first half of their value.

MSalters Over a year ago

std::pair allows you to create "first-second" pairs. The interpretation of pair::first as Key and pair::second as Value is specific to std::map.

jxh · Accepted Answer · 2012-06-11 21:13:03Z

1

Since no one posted it as an answer, sometimes it is convenient to define a macro to create a variable.

#define DEFINE_HELPER(x) Helper helper_##x = Helper(#x)
#define HELPER(x) (&helper_##x)

struct Helper {
    std::string name;
    Helper (const char *s) : name(s) {}
};

DEFINE_HELPER(A);
DEFINE_HELPER(B);

std::cout << HELPER(A)->name << std::endl;

answered Jun 11, 2012 at 21:13

jxh

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