Pick better name for toCheckedValue and fromCheckedValue

[reinco]

Instead of using the cryptic names why do we not just make several template functions, called 'zserio::cast' ?

Example on how the API could look like (no actual numerical range checking is implemented):

template <typename T>
class Number
{
public:   
    using BaseType = T;

    Number(T t) { m_value = t; }

    BaseType value() { return m_value; }
private:   
   BaseType m_value;
};

template <typename T>
T cast(typename T::BaseType value)
{
    return T(value); 
}

template <typename T, typename U = Number<T>>
T cast(U value)
{
    return value.value();
}

int main()
{
    auto v = cast<Number<int>>(4);
    auto w = cast<int>(v);
    return 0;
}

[mikir]

I have two notes regarding this solution:

1. Naming is difficult. From my point of view, cast is cryptic name as well because it is not immediately obvious whether the function performs range checking before casting, which could lead to unexpected behavior. It might be that something like checked_cast will be better.

2. The cast from wrapper type to the native type is a little bit misleading because wrapper type already knows very well the native type. So, it might be better to implement something like this:

   template <typename T>
   T cast(Number<T> value)
   {
       return value.value();
   }
   

   This allows to write something like

   int w = cast<int>(v);
   

   or

   int w = cast(v);
   

   but not something like

   int w = cast<unsigned>(v);
   

   If cast without <int> looks strange, we can disable it. But then, users will have to specify something which might be redundant.