I mentioned earlier wanting to avoid modules for this, and hoping for something like the SML syntax that Richard mentioned, even making my own equivalent syntactic proposal {f = ...; g = ...} where h = ... which looks in line with current Haskell conventions. Given the existing options, however, I would probably go with a top-level pair definition: (f,g) = (..., ...) where h = ... or (f,g) = let f' = ...; g' = ...' ; h = ... in (f',g') as mentioned by Jeff. Thanks to all who contributed! --Todd On Tue, Nov 28, 2023 at 12:40 AM Daniel Casanueva < daniel.casanueva@proton.me> wrote:
I hope I am not misunderstanding the question, but if you want to define f, g and h, but only export f and g, this is what you would do in Haskell:
module Foo.Bar (f, g) where
f = ... g = ... h = ...
The module header determines what gets exported.
On Tuesday, November 28th, 2023 at 07:35, Richard O'Keefe < raoknz@gmail.com> wrote:
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@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@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@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.
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