How do I implement the equivalent of nested Perl hashes in C++?

Question

I want to change some Perl code into C++. I need to know how to implement nested Perl hashes in C++. I thought of STL as a good choice and used maps. With the help of maps I can create only a simple hash but I do not know how to create a nested hash structure.

My Perl hash is like this:

%foo = (
    "bar1" => {
        Default => 0,
        Value   => 0
    },
    "bar2" => {
        Default => 2,
        value   => 5,
        other   => 4
    }
)

I can modify it thus: $foo{"bar1"}->{"Default"} = 15.

How do I do this in C++ using STL? Maybe this is a simple question but I am not able to figure it out.

Answer 1

You may need the type:

std::map< std::string, std::map<std::string, int> > 

You may need to use struct (or class) instead.

struct Element {
    int default;
    int value;
    int other;
    Element(): default(0), value(0), other(0)
    { }
    Element(int default_, int value_, int other_)
    : default(default_)
    , value(value_)
    , other(other_)
    { }
};

int main() {
    std::map<std::string, Element> elements;
    elements["bar1"]; // Creates element with default constructor
    elements["bar2"] = Element(2,5,4);
    elements["bar3"].default = 5; // Same as "bar1", then sets default to 5
    return 0;
}