Re: [Haskell-cafe] Why were unfailable patterns removed and "fail" added to Monad?

On Thu, Jan 19, 2012 at 10:43 PM, Gregory Crosswhite wrote:

first, that the notion of "unfailable" was not removed from the language so much as not added in the first place

No, this is not correct. Unfailable patterns were specified in Haskell 1.4 (or, they were called "failure-free" there; they likely existed earlier, too, but I'll leave the research to people who are interested). They were "new" in the sense that they were introduced only for the purposes of desugaring do/comprehensions, whereas refutable vs. irrefutable patterns need to be talked about for other purposes. -- Dan