[m-dev.] Resources example

[Ian MacLarty]

On 26 Apr 2005, at 14:27, Ian MacLarty wrote:

>
> It sounds like a good idea to me to have two versions of predicates 
> that put constraints on solver_type variables - one version that the 
> user sees which has solver_type arguments and one version that the 
> implementor of the constraint solver sees where the solver_type 
> arguments have their representation types.
>
> I propose extending this concept so that in addition to having 
> representation argument types, the implementor version also has two 
> extra arguments on the end -- representing the state of the solver 
> before and after the constraint is added.  This would present a pure 
> interface to both the implementor and the user without the need for 
> the seperate concept of resources.  When declaring the solve_type 
> you'd need to also declare the type of the constraint solver state, 
> but I think that's probably a good thing.  The compiler could then put 
> in all the impure code to convert the solver type arguments to their 
> representations and retrieve the solver state from a global variable.
>

This would also make debugging of code involving solver types easier.  
Since the compiler would be aware of the constraints store, it would be 
possible to have a "print constraints" command in mdb which would print 
the constraint store for a particular solver_type.  We could also 
display any changes to the constraint store in the declarative 
debugger.

Ian.

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