Records in Haskell -- updating higher-ranked fields: required?

AntC anthony_clayden at
Tue Feb 28 04:45:13 CET 2012

Greg Weber <greg <at>> writes:

> >
> > No, I don't think anybody has a satisfactory approach to
> > updating polymorphic/higher-ranked fields. (DORF mentions
> > one, but it's a ghastly hack.
> So are the proposals dead until this is tackled, or should SORF/DORF
> propose not to allow that?

That's an important question. I've asked in the DORF proposal how big is the 
demand to update h-r fields?

Note that is something you can do currently with H98 records/fields.

Is it good enough to be able to extract and use h-r fields in polymorphic 
contexts? (Both SORF and DORF can do that.)

Is it good enough to be able to create records with h-r fields (using the data 
constructor)?  (Both SORF and DORF can do that.)


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