If we're voting....
I think \of is all right, and multi-argument case could be handy,
which rules out using 'case of' for lambda case, because it's the
syntax for a 0-argument case:
case of
| guard1 -> ...
| guard2 -> ...
Then multi-argument lambda case could use the comma syntax of
multi-argument case.
One thing I don't think makes sense in combination is \of with
0-arguments, since any desugaring of that is not going to involve and
actual lambda expression.
-- Dan
On Thu, Jul 5, 2012 at 5:04 PM, Edward Kmett <[email protected]> wrote:
> I really like the \of proposal!
>
> It is a clean elision with \x -> case x of becoming \of
>
> I still don't like it directly for multiple arguments.
>
> One possible approach to multiple arguments is what we use for multi-argument
> case/alt here in our little haskell-like language, Ermine, here at S&P
> CapitalIQ, we allow for ',' separated patterns, but without surrounding
> parens to be treated as a multi argument case and alt pair. Internally we
> desugar our usual top level bindings directly to this representation. When
> mixed with the \of extension, this would give you:
>
> foo :: Num a => Maybe a -> Maybe a -> Maybe a
> foo = \of
> Just x, Just y -> Just (x*y)
> _, _ -> Nothing
>
> but it wouldn't incur parens for the usual constructor pattern matches and it
> sits cleanly in another syntactic hole.
>
> A similar generalization can be applied to the expression between case and of
> to permit a , separated list of expressions so this becomes applicable to the
> usual case construct. A naked unparenthesized , is illegal there currently as
> well. That would effectively be constructing then matching on an unboxed
> tuple without the (#, #) noise, but that can be viewed as a separate
> proposal' then the above is just the elision of the case component of:
>
> foo mx my = case mx, my of
> Just x, Just y -> Just (x*y)
> _, _ -> Nothing
>
> On Jul 5, 2012, at 2:49 PM, [email protected] wrote:
>
>> Quoting [email protected]:
>>
>>> Well, for what it's worth, my vote goes for a multi-argument \case. I
>>
>> Just saw a proposal for \of on the reddit post about this. That's even
>> better, since:
>>
>> 1. it doesn't change the list of block heralds
>> 2. it doesn't mention case, and therefore multi-arg \of is perhaps a bit
>> less objectionable to those who expect "case" to be single-argument
>> 3. 40% less typing!
>>
>> Can I change my vote? =)
>> ~d
>>
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