Re: [Caml-list] A weird typing error

[Jonathan Protzenko <jonathan.protzenko@gmail.com>]

FWIW it type-checks on a recent trunk build.

jonathan

On Fri 25 May 2012 12:17:33 AM CEST, Philippe Wang wrote:
> Hi,
>
> I re-wrote your program, twice.
>
> First time: The actual problem was submerged... so I removed the
> irrelevant code.
> It became:
>
> type 'a twice = 'a
> class map = object ((self : 'self_type))
>    method twice : 'a0 'b0. ('self_type -> 'a0 -> 'b0) -> 'a0 twice -> 'b0 twice =
>      fun mf_a -> mf_a self
> end
>
> => ocamlc points a surprising error at line 1. I don't quite understand...
>
> Second time: well, line 1 seems fine to me. I added some missing parameters.
> It became:
>
> type 'a twice = 'a
> class map =
> object ((self : 's))
>    method twice : 'a0 'b0. ('s -> 'a0 -> 'b0) -> 'a0 twice -> 'b0 twice =
>      fun mf_a x -> mf_a (self : 's)  (x: 'a0 twice)
> end
>
> => ocamlc points the same error, but at line 5, which is a lot better,
> much less weird...
> Well, kind of same error: the weird (buggy) part of the message is
> removed, the important part is kept.
>
>
> And now... I just don't know why it doesn't type-check. All I have
> left to say is that I hate encoding data into type names. It's fun
> when it works. It's hell otherwise.
>
> I'm curious to understand the solution of this weird problem, if
> someone unravels it.
>
> Cheers.
> Philippe Wang
>
>
>
> On Thu, May 24, 2012 at 7:55 PM, bob zhang <bobzhang1988@gmail.com> wrote:
>>
>> Hi, list
>>      I came across a weird type error.
>>      The error message is  "Error: The implementation type_error_ppo.ml
>>         does not match the interface (inferred signature):"
>>      I attached the file
>>     Many thanks
>>
>> --
>> -- Bob
>