On 07/09/2012 11:22 PM, Wolfgang Jeltsch wrote:
Am Montag, den 09.07.2012, 21:04 +0700 schrieb Mikhail Vorozhtsov:
Could you express your opinion on the case "comma sugar", i.e.
case x, y of P1, P2 -> ... P3, P4 -> ...
as sugar for
case (# x, y #) of (# P1, P2 #) -> ... (# P3, P4 #) -> ...
and respectively
\case P1, P2 -> ... P3, P4 -> ...
as sugar for
\x y -> case x, y of P1, P2 -> ... P3, P4 -> ...
?
Although I wasn’t asked, I want to express my opinion. I think, the use of the comma is strange. When declaring functions with multiple arguments, we don’t have commas:
f Nothing y = y f (Just x) y = x
In lambda expressions for multi-argument functions, we also don’t have commas:
\x y -> x + y
Why should we have them when using a case-lambda expression for a multi-argument function? The trick here is to not start with functions, but with case-expressions. If we introduce "multi-place" case-expressions not as a sugar, but as an extension of regular case-expressions (which may be /implemented/ as a sugar under the hood), then it would be only natural for pattern syntax used with "case" to transfer to lambda-case, as it already does in the current single-argument proposals (no parentheses around patterns). lambda-CASE, not LAMBDA-case (that's why I prefer \case to \of - it says clearly "hey, it's a case expression, expect stuff to be casy").