[boost] Re: Ranged type mini-library submission

From: Robert Bell (belvis_at_[hidden])
Date: 2004-05-17 13:54:38

christopher diggins wrote:
> ----- Original Message ----- 
> From: "Rob Stewart" <stewart_at_[hidden]>
> [snip]
> 
>>That is a problem, but so too is the increasing pain of
>>specifying a desireable combination of policies.  What about
>>using a single policy argument with everything combined?  That
>>means you can use a single class (template) or use a class
>>template that permits specifying various pieces -- not unlike
>>shown above -- into one class that can be the constrained_value
>>parameter.
>>
>>The advantage of this approach is that it gives the policy
>>authors greater flexibility.  They can write monolithic policy
>>classes, if desireable.  They can assemble a class template that
>>gives select configurability or one that makes it possible to
>>supply each policy independently as you've shown.  As part of the
>>library, you could even supply the latter class template, so the
>>library would support both extremes out of the box.
> 
> 
> 
> I agree. I just posted a latest version at
> http://www.cdiggins.com/constrained_value.hpp which has only has two
> policies passed to a constrained_value type, a constraints_policy and an
> implicit_conversion flag. This flag I believe is best left out of the
> constraints_policy but I could be convinced otherwise.
> 
> There is now a small demonstration program at
> http://www.cdiggins.com/cv_test.hpp which has some example policies.

Some quick notes:

-- The default constructor of constrained_value initializes the member 
"m" by calling the min() function, which isn't present.

-- The test program is at http://www.cdiggins.com/cv_test.cpp.

-- In the test program, throwing_invalid_policy should throw 
exception(), not exception, and allowing exception to default to void 
won't compile (can't throw void).

-- throwing_invalid_range just uses "throw;", but doesn't appear to be 
called from inside a catch handler.

Aside from that, it's looking pretty interesting.

Bob