Re: [boost] Ranged type mini-library submission

From: Rob Stewart (stewart_at_[hidden])
Date: 2004-05-24 16:29:46

From: christopher diggins <cdiggins_at_[hidden]>
> 
>     template
>     <
>       class constraints_policy,
              ^^^^^^^^^^^^^^^^^^
I think the usual naming convention would make that
"Constraints" or something similar.

>       bool implicit_conversion_policy = true
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
ditto: "ImplicitConversion"

>     >
>     class constrained_value {
>       private:
>         struct unused_struct { };

Why the "_struct" suffix?  Wouldn't "unused" suffice?

>       public:
>         typedef constrained_value<constraints_policy,
> implicit_conversion_policy> self;
>         typedef typename constraints_policy::value value;
>         typedef typename mpl::if_c<implicit_conversion_policy, value,
> unused_struct>::type value_parameter;

          typedef Constraints constraints_policy;
          typedef ImplicitConversion conversion_policy;

>         static constraints_policy get_constraints() { return
> constraints_policy(); }
>         constrained_value() { }
>         constrained_value(const self& x) { assign(x.get_value()); }
>         constrained_value(value_parameter x) { assign(x); }

What if the type is not a built-in?  That is, what if copying is
expensive?  Use TypeTraits to determine whether to pass by value
or by reference.

>         const value get_value() const { return m; }
>         operator value() { return m; }

Why return by value?  Why not const reference?  Even better, use
TypeTraits to determine whether to return by value or by
reference.

>         self& operator=(const self& x) { assign(x.get_value()); return
> *this; }
>         self& operator=(value_parameter x) { assign(x); return *this; }

Use TypeTraits here, too.

>         void assign(unused_struct x) { }
>         void assign(value_parameter x) { constraints_policy::assign(x, m); }

And here.

Also, it you've shown the arguments in the reverse order from
what I'd expect.  The assignment operator puts the destination on
the left, so I'd expect m on the left.

>       private:
>         value m;
>     };

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;