gistfile1.cpp

class Node;

class FractionalNode {
    virtual double min() = 0;
    virtual double max() = 0;
};

class BooleanNode;

template<class Result>
class If : Result {
    If(BooleanNode condition, Result on_true, Result on_false) {
        static_assert(Result is node);
    }

    // If Result is FractionalNode, impl min, max
}