Re: [boost] [review][constrained_value] Review of Constrained Value Library begins today

Subject: Re: [boost] [review][constrained_value] Review of Constrained Value Library begins today
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-12-06 04:13:09

----- Original Message ----- 
From: "Jeff Garland" <jeff_at_[hidden]>
To: <boost_at_[hidden]>; <boost-users_at_[hidden]>
Sent: Monday, December 01, 2008 1:30 PM
Subject: [boost] [review][constrained_value] Review of Constrained Value Library begins today

Hi,
what do you think about replacing the typedef by a specific class so instead of writing
       bounded<int>::type v;
we write
       bounded<int> v;

The advantage to have a specific class (see below) is that it allows to add specific members that have a sens, e. g. change_lower_bound can be added to bounded<int, int, int> but not to bounded_int<int, 0, 100>.  The liability is that we need to repeat a lot of constructors. Of course this can be done by the user itself as constrained is a public class but at the end what is more important is the user interface.

This technique has already been used at least on Boost.MultiIndex and Boost.Flyweight.

Best regards,
Vicente

================================================
/// The class of constrained for bounded object types (using within_bounds constraint policy).
template <
    typename ValueType,
    typename LowerType = ValueType,
    typename UpperType = LowerType,
    typename ErrorPolicy = throw_exception<>,
    typename LowerExclType = boost::mpl::false_,
    typename UpperExclType = LowerExclType,
    typename CompareType = std::less<ValueType>
>
struct bounded 
        : constrained<
            ValueType,
            within_bounds<
                LowerType,
                UpperType,
                LowerExclType,
                UpperExclType,
                CompareType
            >,
            ErrorPolicy
        >
{

    /// The basetype-typedef alias.
    typedef
        constrained<
            ValueType,
            within_bounds<
                LowerType,
                UpperType,
                LowerExclType,
                UpperExclType,
                CompareType
            >,
            ErrorPolicy
        > basetype;

    // add all the constructors and specific functions
    // ...
};