Template overriding of operator []

[Alexandru Savescu]

Hello, I have a class and I want to override its [] operator. So I did like this:

int operator [] (LPCTSTR x)
{
.....
}

Now I want my operator to return long, doubles, strings etc. I don't want to manually write dozen of operators, but handle it with templates:

template <typename T>
T operator [] (LPCTSTR x)
{
T t;
....
return t;
}

This complies fine. My problem is that I don't know how to call my template operator. I tried:

MyClass m;
m["str"]<int>;
m<int>["str"];
m.operator <int>[] ("str");

but all I got were compiler errors. Any ideas? Thanks Best regards, Alexandru Savescu P.S. Interested in art? Visit this!

[Joaquin M Lopez Munoz]

The syntax for calling your templatized operator is as convoluted as it can get:

m.template operator[]<int>("str");

Unfortunately, VC++ 6.0sp5 does not swallow this (don't know for other MS compilers). An alternative, that also simplifies notation, is as follows:

template <typename T>
struct Type2Type // borrowed from Alexandrescu's "Modern C++ Design"
{
typedef T type;
};

struct MyClass
{
template <typename T> T operator () (const char * x,Type2Type<T>)
{
T t;
...
return t;
}
};

int main()
{
MyClass m;
m("str",Type2Type<int>());
m("str",Type2Type<double>());
return 0;
}

This solution alas drops the nice [] notation in favor of simpler parentheses, but I don't think you have a better alternative. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo