Cale's rationale chimes with me. A lot - I feel like I might have even made
the same point in previous threads on this. I think of the tradeoff like
this:
* The lack of \of doesn't really hurt very much. In fact, arguably by
forcing the author to type some more characters and give something a name,
we get code that's clearer for the reader. (yes this is very subjective,
but syntax is).
* The addition of \of *would* hurt new users of the language. Only a bit,
but every bit makes things worse, and things are already quite bad.
Cheers
Simon
On Thu, 3 Sep 2020 at 23:02, Richard Eisenberg
Hi all,
Proposal #302 was submitted to the committee and assigned to Cale. He has made a recommendation on the GitHub trail, but I don't believe the committee has discussed this among ourselves.
PR: https://github.com/ghc-proposals/ghc-proposals/pull/302 Proposal: https://github.com/JakobBruenker/ghc-proposals/blob/patch-1/proposals/0000-l... Cale's recommendation: https://github.com/ghc-proposals/ghc-proposals/pull/302#issuecomment-6660750...
The idea, in brief, is to introduce a new syntax (guarded behind -XMultiWayLambda) \of. Here is an example, which gives you the idea:
mplus :: Maybe Int -> Maybe Int -> Maybe Int mplus = \of Nothing _ -> Nothing _ Nothing -> Nothing (Just x) (Just y) -> Just (x + y)
The new keyword allows us to use a syntax similar to function definitions, but without repeating the name of the function. It is also like \case, but it allows multiple arguments. Guards are allowed, as usual.
I really like this new syntax -- mostly because I find it very strange that we have to repeat the function name on every line. And then change the spacing when we change the function name. And I like the mnemonic "lambda of". And it allows me to write a where clause that is accessible in multiple different patterns, or an indented where clause that is usable in just one. If it didn't confuse readers, I would use this syntax all the time.
Even so, I agree with Cale's recommendation to reject. We just have too much syntax! If someone were to come along and draft a concrete proposal of how we could, for example, use this syntax to replace both \case and if|, with a migration strategy, etc., then I might be in favor. Until then, I think we've spent our budget for cute, obscure bits of syntax.
Richard _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee