[Caml-list] Re: How to add a hook to Stream.junk?

[bobzhang <bobzhang1988@gmail.com>]

On 11/20/12 8:35 PM, Wojciech Meyer wrote:
> bob zhang <bobzhang1988@gmail.com> writes:
>

>> Hi List,
>>     Does anyone know any trick to add a hook to Stream.junk,  I have
>> tried different ways,  but did not find any solution, yet
>> I want to trigger an action each time when I junk a token from the
>> stream. (copy the whole file from stdlib is fine, but I don't
>> know how to make the type checker happy :-()
>> --
>> Regards
>> -- Bob
>
Greetings,
> You can parametrise the Stream.t type with your desired type and the
> hook.
>
> Then you can substitute type using destructive substitution of a type:
>
> module Stream : module type of Stream with type 'elt t := ('hook, 'elt)
> CustomStream.t = Stream
>
> Finally you can implement your own CustomStream.junk function that
> operates on the parametrised type and include the CustomStream module.
>
> This should work, but I've not tested or compiled it.
>
Stream specialized on char stream :-(

> --
> Wojciech Meyer
> http://danmey.org
>