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

Henrik Nilsson Henrik.Nilsson at nottingham.ac.uk
Tue Oct 6 11:32:31 UTC 2015

Dear all,

Executive Summary: Please let us defer further discussion
and ultimate decision on MRP to the resurrected HaskellPrime

While we can discuss the extent of additional breakage
MRP would cause, the fact remains it is a further
breaking change. A survey of breakage to books as
Herbert did is certainly valuable  (thanks!), but
much breakage will (effectively) remain unquantifiable.

It is also clear from the discussions over the last
couple of weeks, on the Haskell libraries list as well
as various other forums and social media, that MRP is
highly contentions.

This begs two questions:

   1. Is the Haskell Libraries list and informal voting process
      really an appropriate, or even acceptable, way to adopt
      such far-reaching changes to what effectively amounts to
      Haskell itself?

   2. Why the hurry to push MRP through?

As to question 1, to Graham Hutton's and my knowledge,
the libraries list and its voting process was originally
set up for 3rd-party libraries in fptools. It seems to
have experienced some form of "mission creep" since.
Maybe that is understandable given that there was no
obvious alternative as HaskellPrime has been defunct
for a fair few years. But, as has been pointed out in a
number of postings, a lot of people with very valuable
perspectives are also very busy, and thus likely to
miss a short discussion period (as has happened in the
past in relation to the Burning the Bridges proposal)
and also have very little time for engaging in long and
complicated e-mail discussions that, from their
perspective, happen at a completely random point in
time and for which they thus have not had a chance to
set aside time even if they wanted to participate.

Just as one data point, AMP etc. mostly passed Graham
and me by simply because a) we were too busy to notice
and b) we simply didn't think there was a mandate for
such massive overhauls outside of a process like
HaskellPrime. And we are demonstrably not alone.

This brings us to question 2. Now that HaskellPrime is
being resurrected, why the hurry to push MRP through?
Surely HaskellPrime is the forum where breaking
changes like MRP should be discussed, allowing as much
time as is necessary and allowing for an as wide range
of perspectives as possible to properly be taken into

The need to "field test" MRP prior to discussing
it in HaskellPrime has been mentioned. Graham and I
are very sceptical. In the past, at least in the
past leading up to Haskell 2010 or so, the community
at large was not roped in as involuntary field testers.

If MRP is pushed through now, with a resurrection of
HaskellPrime being imminent, Graham and I strongly believe
that risks coming across to a very large part of the
Haskell community as preempting proper process by facing
the new HaskellPrime committee with (yet another) fait

Therefore, please let us defer further discussion and
ultimate decision on MRP to the resurrected
HaskellPrime committee, which is where it properly
belongs. Otherwise, the Haskell community itself might
be one of the things that MRP breaks.

Best regards,


Henrik Nilsson
School of Computer Science
The University of Nottingham
nhn at cs.nott.ac.uk

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