C++ auto conversions

Question

For two unrelated classes "class A" and "class B" and a function

B convert(const A&);

Is there a way to tell C++ to automatically, for any function that takes "class B" as argument, to auto convert a "class A".

Thanks!

Answer 1

What you would normally do in this case is give B a constructor that takes an A:

class B
{
public:
    B(const A&);
};

And do the conversion there. The compiler will say "How can I make A a B? Oh, I see B can be constructed from an A".

Another method is to use a conversion operator:

class A
{
public:
    operator B(void) const; 
}

And the compiler will say "How can I make A a B? Oh, I see A can be converted to B".

Keep in mind these are very easy to abuse. Make sure it really makes sense for these two types to implicitly convert to each other.