[Haskell-cafe] Monad of no `return` Proposal (MRP): Moving `return` out of `Monad`

Christopher Allen cma at bitemyapp.com
Mon Oct 5 19:08:09 UTC 2015

I'm writing a book (http://haskellbook.com/) with my coauthor. It is up to
date with GHC 7.10. AMP made things better, not harder, with respect to
teaching Haskell. BBP required some explanation of "ignore this type, we're
asserting a different one", but the positives are still better than the

Please don't use existing or forthcoming books as an excuse to do or not-do
things. Do what's right for the users of the language.

On Mon, Oct 5, 2015 at 2:01 PM, Johan Tibell <johan.tibell at gmail.com> wrote:

> On Mon, Oct 5, 2015 at 8:34 PM, Gregory Collins <greg at gregorycollins.net>
> wrote:
>> On Mon, Oct 5, 2015 at 8:09 AM, Gershom B <gershomb at gmail.com> wrote:
>>> My understanding of the argument here, which seems to make sense to me,
>>> is that the AMP already introduced a significant breaking change with
>>> regards to monads. Books and lecture notes have already not caught up to
>>> this, by and large. Hence, by introducing a further change, which
>>> _completes_ the general AMP project, then by the time books and lecture
>>> notes are all updated, they will be able to tell a much nicer story than
>>> the current one?
>> This is a multi-year, "boil the ocean"-style project, affecting literally
>> every Haskell user, and the end result after all of this labor is going to
>> be... a slightly spiffier bike shed?
>> Strongly -1 from me also. My experience over the last couple of years is
>> that every GHC release breaks my libraries in annoying ways that require
>> CPP to fix:
>> ~/personal/src/snap λ  find . -name '*.hs' | xargs egrep
>> '#if.*(MIN_VERSION)|(GLASGOW_HASKELL)' | wc -l
>> 64
>> As a user this is another bikeshedding change that is not going to
>> benefit me at all. Maintaining a Haskell library can be an exasperating
>> exercise of running on a treadmill to keep up with busywork caused by
>> changes to the core language and libraries. My feeling is starting to
>> become that the libraries committee is doing as much (if not more) to
>> *cause* problems and work for me than it is doing to improve the common
>> infrastructure.
> On the libraries I maintain and have a copy of on my computer right now:
> 329
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Chris Allen
Currently working on http://haskellbook.com
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