This is a simple experimental implementation of a LINQ-like query language for C++ containers. I’ve just started working on it, so it’s still just a toy. Linq++ depends on the Boost C++ library.

Suppose you have an STL container:

struct Person {
    string name;
    int age;
    Person(const string& aName, int anAge) : name(aName), age(anAge) {}
};
shared_ptr<vector<Person> > guests;

You can do simple things like:
Count the number of people older than 30

cout << from(guests)
        .where(&_1 ->* &Person::age > 30)
        .count()

Find people older than 30 and create a vector with their ages

from(guests)
        .where(&_1 ->* &Person::age > 30)
        .select<int>(&_1 ->* &Person::age);

A snippet from the unit tests illustrates its expressivenss:

// combine the people older than 30 with the person with name "joe" into one table.
DataSet<vector<Person> > results =
        insert(
                from(guests)
                .where(&_1 ->* &Person::age > 30))
        .into(
                from(guests)
                .where(&_1 ->* &Person::name == "joe"));
// select the age column from the previous table.

shared_ptr<vector > ages = results

                                .select(&_1 →* &Person::age)

                                .get();

See the companion unit tests for details.