Re: [Cppcms-users] Migration Guide

[Artyom B. <art...@ya...>]

> From: Markus Raab <us...@ma...>
>
> First of all, congratulation for cppcms 1.0.
> It is a really great piece of software!


Thanks... :-)

> 
> Ok, I understand. I am rather a fan of Scott Meyers: Use const whenever
> possible.
> 

The biggest problem is that const does not
really works well with pimpl-design. Because with pipml
almost everything can be const however semantically it may
be non-const:

For example the following construction is 100% correct from C++
point of view (d is not changed) but semantically it is by no
means const.

  class foo {
  public:
    ...
    void bar() const
    {
      d->x++;
    }
    ...
  private:
    ...
    struct impl  { int x; };
    impl *d;
  };


So you can easily make wrong assumptions based on const or
non-const interface.

Const works very well for real data structures but it is not the
best for complex systems with complex relations.

For example classes like `cppcms::json::value` or `cppcms::http::cookie`
have dual const/non-const interface because they are data structures.

But many classes do not have such clear and easy separation.

Best,
  Artyom