How can I implement a map with different data types as values?

Question

I want to put two (not more) different data types as values into a map as shown in the following example:

typeX A, B, ...;
typeY Z, Y, ...;

void func (typeX) { ... }
void func (typeY) { ... }

std::map <std::string, what_to_put_here??> map;
map["a"] = A;
map["z"] = Z;
...

std::vector<std::string> list;
// This list will be something like "a", "y", ...

for (unsigned int i = 0; i < list.size(); ++i)
    func( map[list[i]] )

Obviously this doesn't work, as the map will only accept one data type of value. However, when looping over list, the call to func() should be unambiguous since the type of map[list[i]] is known.

I want to avoid explicit casting or type checking, i.e. something like this:

if (typeid( map[list[i]] ).name() == "typeX")
    func( map[list[i]] )
else if (typeid( map[list[i]] ).name() == "typeY")
    func( map[list[i]] )

Is this possible? Again, it will be limited to only two different data types.

Answer 1

You want to use boost::variant:

std::map <std::string, boost::variant<typeX, typeY>>