Yes I agree with Tom; it's at least a bit unexpected because unlike with records, there is (if I understand well) nothing I can write inside the {} that would actually be valid for that type. On Thu, 30 Nov 2023 at 14:06, Tom Ellis < tom-lists-haskell-cafe-2023@jaguarpaw.co.uk> wrote:
It was unexpected to me because A1 and A2 were not defined as record constructors. (Since I discovered it I now use it regularly; it's very nice.)
On Thu, Nov 30, 2023 at 02:58:43PM +0100, David Kraeutmann wrote:
Yes. You're just using record pattern match with no records. Why would it be unexpected?
On 30.11.2023 14:46, Noon van der Silk wrote:
Sometimes I have a type like:
data A = A1 Int | A2 Int Int
Then if I want to do pattern matching and ignore the parameters I do:
f (A1 _) = .. f (A2 _ _) = ...
But that's annoying; I need to remember how many parameters each one has!
Yesterday I learned I can just do this:
f A1 {} = ... f A2 {} = ...
And GHC is happy.
Is this expected? Am I the last to learn about this trick?
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-- Noon van der Silk, ن http://silky.github.io/ "My programming language is kindness."