[Haskell-cafe] Mutual scoping question

[Richard O'Keefe]

SML has
   local
      declarations
   in
      declarations
   end
and there is no fundamental reason why Haskell couldn't.
Is there some reason why you cannot put f g and h in a module and just
export f and g?

On Thu, 23 Nov 2023 at 16:42, Todd Wilson <twilson at csufresno.edu> wrote:
>
> It seems (surprisingly to me) that such pattern matches are allowed at the top level, so that would simplify my kludge a bit by skipping the definition of fg. But is using pairs (or the equivalent) in this way the only solution? I was hoping that there might be some kind of top-level definition syntax like
>
> {f .. = ... ; g .. = ...} where h .. = ...
>
>  that would correctly capture the scoping I'm looking for.
>
> --Todd
>
> On Wed, Nov 22, 2023 at 5:43 PM Jeff Clites <jclites at mac.com> wrote:
>>
>> Can you do:
>>
>>   (f, g) = let f’ = … in (f’, g’)
>>
>> or is a pattern match not allowed at top level?
>>
>> Jeff
>>
>> On Nov 22, 2023, at 4:40 PM, Todd Wilson <twilson at csufresno.edu> wrote:
>>
>> 
>> Hello, Cafe:
>>
>> Is there a preferred way to define two top-level mutually recursive functions, f and g, that both use a common local function h such that h is (1) only defined once and (2) does not escape the scope of f and g? I suppose it could be done like this:
>>
>> fg = let f ... = ... f,g,h ...
>>          g ... = ... f,g,h ...
>>          h ... = ... h ...
>>       in (f,g)
>> f = fst fg
>> g = snd fg
>>
>>
>> but is there something more elegant than this that I'm not seeing?
>>
>> Todd Wilson
>> _______________________________________________
>> Haskell-Cafe mailing list
>> To (un)subscribe, modify options or view archives go to:
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>> Only members subscribed via the mailman list are allowed to post.
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.