I have seen some talk about fixing this, but none anywhere close to reality. As
far as what you can use now, there are several libraries implementing
alternatives to records; 'vinyl' uses type-level literal strings and is very
slick (although all fields with the same name have the same type), while
'fields' uses template Haskell (and I think there are some others as well). I
have used 'vinyl' a fair amount with great success; the others I cannot
evaluate from experience.
-IRS
________________________________________
From: haskell-cafe-boun...@haskell.org [haskell-cafe-boun...@haskell.org] on
behalf of Johannes Waldmann [waldm...@imn.htwk-leipzig.de]
Sent: Tuesday, April 16, 2013 8:17 AM
To: haskell-cafe@haskell.org
Subject: [Haskell-cafe] data types with overlapping component names (in one
module)?
What is the current situation: can we have two types
with overlapping component names in one module?
module M where
data T1 = C1 { foo :: Int }
data T2 = C2 { foo :: String }
It seems not (ghc says: Multiple declarations of 'foo'). This comes close:
http://www.haskell.org/ghc/docs/7.6.2/html/users_guide/syntax-extns.html#disambiguate-fields
but still requires the definitions to reside in different modules?
This is a major pain (it forces me to spread the source over several files),
and also a show-stopper when selling Haskell to OO folks, who "naturally"
assume that a class also denotes a scope. (And that you could nest them.)
Are/were there plans/proposals to address this?
- J.W.
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