| Proposal: FirstClassFieldUpdates
|
| Summary:
| Add some syntax that makes field updates into functions.
I'm wary about occupying too much "syntactic space" with Haskell's named-field
notation. If you had a keyword, like
update { foo = bar }
meaning
\x. x { foo = bar }
that'd get you into a new syntactic space. But braces alone are so precious
that I'm not sure that record updates justify consuming them.
On a related matter, people want to use record syntax for GADTs and
existentials. For record selection and construction these are more or less
fine (ie one can make a sensible spec). But record update is another matter.
Haskell 98 says that record update can change the type of a record (contrary to
some posts in this thread), but the specification becomes really rather tricky
for GADTs and existentials. Indeed, I was going to propose that in H Prime we
might consider making update *not* change the type, backing away from the
current H98 story, but one that makes the spec a lot easier. But various
people have been arguing in favour of the H98 story so I may have an uphill
struggle!
Simon
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