Re: [Haskell-cafe] data types with overlapping component names (in one module)?
True, and thank you for clarifying that. I was thinking of the names of the
field data, not the type-level name of the field:
name = Field :: name ::: String
-IRS
From: acow...@gmail.com [acow...@gmail.com] on behalf of Anthony Cowley
[acow...@seas.upenn.edu]
Sent: Tuesday, April 16, 2013 6:13 PM
To: Sturdy, Ian
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] data types with overlapping component names (in one
module)?
On Tue, Apr 16, 2013 at 4:05 PM, Sturdy, Ian sturdy...@mail.wlu.edu wrote:
'vinyl' uses type-level literal strings and is very slick (although all
fields with the same name have the same type)
This is not entirely true, depending on what you mean by name. The
following is just fine. You only have naming issues if you want to
give @Field::baz:::Int@ a name, that name is, unsurprisingly, tied
to the field type of Int.
{-# LANGUAGE DataKinds, TypeOperators #-}
import Data.Vinyl
type Foo = '[baz ::: Int]
type Bar = '[baz ::: String]
x :: PlainRec Foo
x = Field =: 2
y :: PlainRec Bar
y = Field =: Two
Anthony
-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.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] data types with overlapping component names (in one module)?
I'll just leave it here: http://hackage.haskell.org/trac/ghc/wiki/Records ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] data types with overlapping component names (in one module)?
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.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] data types with overlapping component names (in one module)?
On Tue, Apr 16, 2013 at 4:05 PM, Sturdy, Ian sturdy...@mail.wlu.edu wrote:
'vinyl' uses type-level literal strings and is very slick (although all
fields with the same name have the same type)
This is not entirely true, depending on what you mean by name. The
following is just fine. You only have naming issues if you want to
give @Field::baz:::Int@ a name, that name is, unsurprisingly, tied
to the field type of Int.
{-# LANGUAGE DataKinds, TypeOperators #-}
import Data.Vinyl
type Foo = '[baz ::: Int]
type Bar = '[baz ::: String]
x :: PlainRec Foo
x = Field =: 2
y :: PlainRec Bar
y = Field =: Two
Anthony
-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.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
