Using Monads in C++ to Solve Constraints: Refactoring

    Functional programs are amazingly easy to factorize. Anybody
    who tried to factorize C++ code can testify to how hard it is, 
    and how long it takes to iron out all the bugs introduced 
    by factorization. With functional code, it’s a breeze.

Is it really "with functional code" or more "with toy problems that never had performance related changes made to it?"