Re: [Caml-list] Trouble with subtyping

[Guillaume Yziquel <guillaume.yziquel@citycable.ch>]

Le Thursday 07 Apr 2011 à 18:48:45 (+0200), Pierre-Alexandre Voye a écrit :
>    Hi all, I'm working on a lib to modelize a Multi-Agent System where
>    each agent are driven by a Hierarchical Finite State Machine (HFSM).

Hi.

>    class agent :
>      object
>        val mutable birthtime : int
>        val mutable currentState : agent state option

OK.

>    So, it doesn't want to accept currentState to become a inheritedDwarf
>    state option and thus, I can't use my inheritedDwarf

Not surprising.

'class agent' defines a class, i.e. a piece of code that can be
inherited.

As of now, the currentState field mentions the type 'agent', so if you
inherit from 'agent', currentState field will keep 'agent'.

If you want the field to refer to a subclass, do, in the signature:

class agent : object ('self)
	val mutable birthtime		: int
	val mutable currentState	: 'self state option
	...

>    Pierre-Alexandre
>    --
>    ---------------------
>    Isaac Project - [1]http://www.lisaac.org/

-- 
     Guillaume Yziquel