Re: Removing MonadFail from Monad

On 17.12.2013 00:32, Roman Cheplyaka wrote:

* David Luposchainsky [2013-12-16 23:57:19+0100]

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I don't understand the restriction "is defined via data" since I am not aware of defining constructors outside of data or with something other than the data keyword. Please clarify.

I meant "data and not newtype". If "Only" is a newtype data constructor, the pattern is irrefutable by design, is it not?

One notable case of one-constructor types defined not via data is tuples. You certainly don't want warnings for that!

Should not tuple types be understood as data (,) a b = (,) a b data (,,) a b c = (,,) a b c making them one-constructor types?!

Regarding newtypes vs data, I'm not so sure it should make a difference. It's customary to make one-field types newtypes, and then, if one realizes that more fields are needed, turn them into proper data types.

I agree. What operational semantics is concerned (this mean the execution model of Haskell in the programmer's mind), newtype = data Cheers, Andreas -- Andreas Abel <>< Du bist der geliebte Mensch.