Re: [Savonet-users] Creating a reference for an on_connect function

[David B. <dav...@gm...>]

Hi Leonard,

Using a reference to break this circularity problem is the right
solution. We don't have a simpler solution for now, although we have
this in mind for a few potential language extensions.

On Wed, Mar 20, 2013 at 12:38 AM, Leonard de Ruijter
<lee...@le...> wrote:
> register_source=ref fun ()->()
> src = input.harbor(...,on_connect=!register_source())
> register_source:=see function above
> I however don't know how to create the reference variable itself. I get
> this kind of errors:
> At line 44, char 16-17:
>    this value has type
>      ref((...)->unit) (infered at line 31 char 17 - line 36 char 3)
>    but it should be a subtype of (the type of the value at line 44 char
> 16 - line
>   50 char 3)
>      ref((...)->source(_))

It's probably only a "small" syntax or type error. For instance, you
cannot write !register_source(), it is understood as
!(register_source()). Unfortunately, you cannot fix it by writing
(!register_source)() either -- it's a rigidity of our syntax that is
necessary to allow nice things such as not writing semicolons after
each instruction. Finally, on_connect takes an argument but your
register_source function does not.

Long story short, I recommend writing it as follows:

register_source = ref (fun () -> ())
def call_register_source(_)
  f = !register_source
  f()
end
src = input.harbor(...,on_connect=call_register_source)
register_source := ...

Hope this helps,
-- 
David