Re: [Caml-list] help with functors

[Yotam Barnoy <yotambarnoy@gmail.com>]

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I've been given the solution to the problem, so no need to worry about it
anymore: I was leaving the inner types of InnerBag and ValueBag abstract.
Sorry for the noise.


On Thu, Sep 4, 2014 at 9:39 PM, Yotam Barnoy <yotambarnoy@gmail.com> wrote:

> I've created a gist at
> https://gist.github.com/anonymous/cbfe96b920f08208e1dc to illustrate the
> problem. I can't get  InnerBag to unify with the ValueBag. This is a very
> sparse representation of the code, but it contains all the essential
> elements in one file, so you can just try to build it with ocamlc.
>
> Thanks in advance
> Yotam
>
>
> On Thu, Sep 4, 2014 at 5:59 PM, Yotam Barnoy <yotambarnoy@gmail.com>
> wrote:
>
>> Thanks for the reply Gabriel. I can't post the code at this time -- not
>> without leaving out a whole bunch of it, in which case getting it to
>> compile will be difficult. The pattern should be clear enough, though:
>> ocaml uses functors for all complex persistent data structures, and if I
>> have a Map.Make(something), and then another functorized module that
>> contains Map.Make(something), there should be a way to unify the outer and
>> inner Map. That's basically my situation, but ocaml refuses to unify the
>> two Map applications.
>>
>> Also, there are also very few resources online about complex uses of
>> functors. Almost every resource touches trivial uses and then moves on to
>> other subjects.
>>
>>
>> On Thu, Sep 4, 2014 at 11:12 AM, Gabriel Scherer <
>> gabriel.scherer@gmail.com> wrote:
>>
>>> (voluntarily private reply)
>>>
>>> Could you send a self-contained source code that can be compiled (.. and
>>> maybe raise a type error)? Your code above is good but there are ellipsis
>>> that people maybe don't want to have to fill themselves to experiment with
>>> your problem.
>>>
>>>
>>> On Thu, Sep 4, 2014 at 3:53 PM, Yotam Barnoy <yotambarnoy@gmail.com>
>>> wrote:
>>>
>>>> Here's an attempt to clarify the question:
>>>>
>>>> I have a functor F and a functor G. I apply F to module M outside of G
>>>> to create F', and within G I also apply F to M to create F''. Additionally,
>>>> G is applied to M to create G'. How do I make the compiler understand that
>>>> F' outside G' is the same as F'' inside G'?
>>>>
>>>> Yotam
>>>>
>>>>
>>>> On Wed, Sep 3, 2014 at 1:20 PM, Yotam Barnoy <yotambarnoy@gmail.com>
>>>> wrote:
>>>>
>>>>> Working with ocaml's functional data structures has quickly become a
>>>>> job of connecting different functors together, and I'd appreciate some help.
>>>>>
>>>>> I have the following layout:
>>>>>
>>>>> module rec OrderedKey : OrderedKeyType = struct
>>>>>     type t = Value.value_t
>>>>>     let compare = compare
>>>>>     let filter_idxs idxs = function
>>>>>       | Value.VTuple l -> Value.VTuple(list_filter_idxs idxs l)
>>>>>       | _ -> invalid_arg "not a vtuple"
>>>>>     end
>>>>>
>>>>> and ValueBag : IBag.S with type elt = Value.value_t =
>>>>>   IBag.Make(OrderedKey)
>>>>>
>>>>> and ValueMMap : IMultimap.S with type elt = Value.value_t and type bag
>>>>> = ValueBag.t =
>>>>>   IMultimap.Make(OrderedKey)
>>>>>
>>>>> and Value : sig ... type value_t = ... end = Value
>>>>>
>>>>> The situation is as such: my multimap (IMultimap) contains an internal
>>>>> specialization of the IBag functor called an InnerBag. It attempts to
>>>>> return said bag, which is equivalent to the external ValueBag in structure.
>>>>> However, I don't know how to tell ocaml that the type 'bag' which is
>>>>> abstract in IMultimap is exactly the same as the external ValueBag. I tried
>>>>> to do that above, but what I get is a mismatch between IMultimap's internal
>>>>> InnerBag.t and the external ValueBag.t.
>>>>>
>>>>> Any help would be appreciated.
>>>>>
>>>>> Yotam
>>>>>
>>>>>
>>>>
>>>
>>
>

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