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

Simon Thompson s.j.thompson at kent.ac.uk
Mon Oct 5 09:59:46 UTC 2015

Hello all. I write this to be a little provocative, but …

It’s really interesting to have this discussion, which pulls in all sorts of well-made points about orthogonality, teaching, the evolution of the language and so on, but it simply goes to show that the process of evolving Haskell is profoundly broken. 

Other languages do evolve, but in a managed and reflective way. Simply throwing in changes that would have a profound impact on systems that are commercially and potentially safety critical in an à la carte, offhand, way seems like a breakdown of the collective responsibility of the Haskell community to its users and, indirectly, to its future.

If we make claims - I believe rightly - that Haskell is hitting the mainstream, then we need to think about all changes in terms of the costs and benefits of each of them in the widest possible sense. There’s an old fashioned maxim that sums this up in a pithy way: “if it ain’t broke, don’t fix it”.

Simon Thompson

> On 5 Oct 2015, at 10:47, Michał J Gajda <mjgajda at gmail.com> wrote:
> Hi,
> As a person who used Haskell in all three capacities (for scientific research, for commercial purpose, and to introduce others to benefits of pure and strongly typed programming), I must voice an supportive voice for this change:
> 1. Orthogonal type classes are easier to explain.
> 2. Gradual improvements helps us to generalize further, and this in turn makes education easier.
> 3. Gradual change that break only a little help to prevent either stagnation (FORTRAN) and big breakage (py3k). That keeps us excited.
> That would also call to split TCs into their orthogonal elements: return, ap, bind having the basic TC on their own.
> So:
> +1, but only if it is possible to have compatibilty mode. I believe that rebindable syntax should allow us to otherwise make our own prelude, if we want such a split. Then we could test it well before it is used by the base library.
> That said, I would appreciate Haskell2010 option just like Haskell98 wad, so that we can compile old programs without changes. Even by using some Compat version of standard library. Would that satisfy need for stability?
> PS And since all experts were beginners some time ago, I beg that we do not call them "peripheral".
> --
>   Best regards
>     Michał
> On Monday, 5 October 2015, Malcolm Wallace <malcolm.wallace at me.com <mailto:malcolm.wallace at me.com>> wrote:
> On other social media forums, I am seeing educators who use Haskell as a vehicle for their main work, but would not consider themselves Haskell researchers, and certainly do not have the time to follow Haskell mailing lists, who are beginning to say that these kinds of annoying breakages to the language, affecting their research and teaching materials, are beginning to disincline them to continue using Haskell.  They are feeling like they would be 
> (...) 
> -- 
>   Pozdrawiam
>     Michał
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Simon Thompson | Professor of Logic and Computation 
School of Computing | University of Kent | Canterbury, CT2 7NF, UK
s.j.thompson at kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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