Records in Haskell

Anthony Clayden anthony_clayden at
Fri Jan 27 01:42:03 CET 2012

Ryan Newton <rrnewton <at>> writes:

> I admit I'm a big fan of polymorphic extension.  But I
don't love it enough 
for it to impede progress!  
> Regarding extension:  In trying to read through all this
material I don't 
see a lot of love for "lacks" constraints a la TRex.  
> Cheers,
>   -Ryan
Hi Ryan, I think the "lacks" constraint is sadly
misunderstood, and in fact 
something like it will be needed eventually.

[A thousand apologies for the multiposts! somewhere between
gmaniac and pipermail,
 half my posts are going missing: I was only just warming up
this far. Try again ... again ... third time]

(If anybody who knows the internals of Hugs/TRex is
listening, it would be 
great to get confirmation of the following.)

As you say, it relates to whatever might happen for
polymorphic records, so is 
outside the scope of what SPJ is trying to address in this

On the other hand, let's try to avoid developing an approach
for 'Records in 
Haskell' that has to be undone when/if we get more

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