On Tue, Feb 3, 2015 at 8:32 PM, davean <davean@xkcd.com> wrote:
> On Tue, Feb 3, 2015 at 2:20 PM, Erik Hesselink <hesselink@gmail.com> wrote:
>>
>> > 2. Breakage of existing tutorials/documentation
>>
>> I was just wondering which of these you were alluding to. Turns out
>> it's all of them :) I'm surprised you mention breakage of code, since
>> in my experience most of the breakage in GHC 7.10 I've seen in my own
>> packages and the Stackage builds is due to other factors: the
>> Applicative/Monad changes, time 1.5, etc. It would be interesting (but
>> time consuming) to gather some statistics on this. The breakage of
>> tutorials is unfortunate, yes.
>
>
> So how bad is the breakage of tutorial code really? Looking around almost
> all of it has a full top level type which makes it still work. I've only
> looked for a few minutes but my first impression is that not much breaks
> with this. Is this just a theory or have people actually determined that
> tutorial code breaks?
>
> (Actually, I've found plenty of broken tutorial code, but it wasn't due to
> anything in prelude. Our standard library churn seems much worse on
> tutorials I've looked at then this seems to be.)

I think the 'breakage' is mostly used as mentioning things that work
on lists, while they now work on Foldable/Traversables. For example,
LYAH mentions "length takes a list and returns its length,
obviously.", which isn't true anymore in the strictest sense, it takes
any Foldable. However, you could argue that this text is just
specialization, and that it's still true. There seem to be no things
that are generalized in the section about types, and soon after type
classes are already introduced.  Real World Haskell is slightly more
"broken", for example, it lists:

ghci> :type null
null :: [a] -> Bool

Which isn't true anymore, it would now give "Foldable t => t a -> Bool".

Regards,

Erik

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