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: 2008-12-05 02:28:31

----- 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,

There is a thing that i don't like in the design, the fact that you can change the constraint at runtime. I would prefer to have two separated hierarchies, one for constrained values that preserv its constraints, error handling, ... staticaly, and one for those tyhe constraint can be changed at runtime. I expect that the preserving constrained values be implemented in a more space and time efficient way. 

constrained_value ::= static_type | dynamic_type

For the constrained values that can change its constraint at runtime I see two cases, the constraint is attached to the instance, which is your case, or it attached to a type. 

mutating_type :== by_instance | by_type

When attached to a type, the type needs to maintain the set of instances. Instead of changing the type a split operation can be provided  resulting in a transfer of the instances satisfying the new constraint to the new type. Of course this meens more space and time consumming, but ...

Best regards,

Vicente