Is there some ninja trick to make a variable constant after its declaration?

Question

I know the answer is 99.99% no, but I figured it was worth a try, you never know.

void SomeFunction(int a)
{
    // Here some processing happens on a, for ex         


        

Answer 1

Why not refactor your code in to two separate functions. One that returns a modified a and another that works on this value (without ever changing it).

You could possibly wrap your object too around a holder class object and work with this holder.

template 
struct Constify {
    Constify(T val) : v_( val ) {}
    const T& get() const  { return v_; }
};

void SomeFuncion() {
    Constify ci( Compute() ); // Compute returns `a`
    // process with ci
}

Your example has an easy fix: Refactoring.

// expect a lowercase path or use a case insensitive comparator for basic_string
void OpenFile(string const& path)  
{        
    // I want path to be constant now
    ifstream ...
}

OpenFile( boost::to_lower(path) ); // temporaries can bind to const&