Add missing Monad/Traversable instances to tuples

Henrik Nilsson Henrik.Nilsson at
Thu Apr 4 12:24:30 UTC 2019


Andreas Abel wrote:

 > Abusing tuples for the writer monad was a bad idea in the first place.
 > There is no need to drive a bad idea further to the bitter end.
 > Another way to put it:
 > Not everything that is mathematically consequential is good software 
 > engineering practice.

I could not agree more. Except that I hold that the mathematical
consequence in this case only makes sense if a very particular
perspective is adopted. From other, equally valid, perspectives,

     sum (2,3) = 3

etc. is simply nonsensical.

-1 from me too.

And for the record:

Ganesh Sittampalam replied replied to Carter Schoenwald:
 > > to be clear, the arguments against are valid, but i thnk they could
 > > be
 > > addressed by identifying the changes / tooling that would enable a
 > > better fitting of intent. buggy code happens, fix the root, not the
 > > symptom
 > For the record I think the root cause here *is* the instances, and
 > anything we do later is just sticking plaster. In my mind the
 > instances are the moral equivalent of using dynamic types.

I fully agree with this too, and if the only purpose of the
proposed tooling indeed is to be a "plaster" for users who
accidentally get hurt by sharp edges that really should not be
there in the first place, then that seems to be not only
wholly unnecessary, but a downright dangerous direction.



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