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

[Herbert Valerio Riedel]

On 2015-10-06 at 05:43:43 +0200, Rustom Mody wrote:

[...]

> The python 2→3 transition may have caused some pain to some. However it
> would have been far more difficult if they had not provided tools like
> 2to3 and six:
> https://docs.python.org/2/library/2to3.html
> http://pythonhosted.org/six/
>
> Since the change here is trivial and pervasive why is such a tool not being
> considered?
> [Or have I missed the discussion?]

It is being considered! :-)

I'm in the process of collecting rewrite recipes and samples on

  https://github.com/hvr/Hs2010To201x

Alan is looking into how HaRe can be leveraged for this. I've refrained
from bringing this up, as I'm still waiting to reach a proof-of-concept
stage where we can confidently say that this actually works.


> In particular we can envisage a tool say 8to10 that has these modes
> (command-line flags)
> --portable
> --readable
> --info
>
> with the idea that
> - portable is most unreadable (ifdef litter)
> - readable is not portable -- generate a copy of the whole source tree that
> will have the changes and not be compatible for ghc < 7.8
>   This is for those library authors that prefer to maintain a clean code
> base and hell with earlier ghc versions
> - info summarizes which files would change and how so that a suitable
> reorganization of the files/directories can be done prior to the switch
>   This is for those library authors that would like to take the trouble to
> have a compatibility layer and have code as readable as possible overall
>
> [Whether pure is really preferable to return is another matter --
> For me one of the strongest criticisms of the python 2→3 switch is this
> that if they were going to break things anyhow why was the cleanup not more
> far-reaching?
>
> Lets keep this note in these parentheses :-)
>
> ]
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-- 
"Elegance is not optional" -- Richard O'Keefe