gmane.comp.lang.haskell.libraries

Scott Dillard | 16 May 18:14

IntMap intersectionWith type is too restrictive

Hi,

This is a simple bug report, more or less. The type of
Data.IntMap.intersectionWith is too restrictive. Presently (GHC 8.2,
http://darcs.haskell.org/packages/containers/Data/) it's declared as
(a->b->a) -> IntMap a -> IntMap b -> IntMap a, but if you just remove
the type declarations it's inferred as (a->b->c) -> IntMap a -> IntMap
b -> IntMap c. Similarly for intersectionWithKey. The more general
a->b->c type is also the type of Data.Map.intersectionWith, and it's
quite useful, such as (intersectionWith (,))

Scott

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Don Stewart | 16 May 19:28

Re: IntMap intersectionWith type is too restrictive

sedillard:
> Hi,
> 
> This is a simple bug report, more or less. The type of
> Data.IntMap.intersectionWith is too restrictive. Presently (GHC 8.2,
> http://darcs.haskell.org/packages/containers/Data/) it's declared as
> (a->b->a) -> IntMap a -> IntMap b -> IntMap a, but if you just remove
> the type declarations it's inferred as (a->b->c) -> IntMap a -> IntMap
> b -> IntMap c. Similarly for intersectionWithKey. The more general
> a->b->c type is also the type of Data.Map.intersectionWith, and it's
> quite useful, such as (intersectionWith (,))

Can you submit a patch? This kind of thing comes up occasionally,
and generalising the type is often safe and easy.

-- Don

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Scott Dillard | 16 May 20:03

Re: IntMap intersectionWith type is too restrictive

[generalized type of IntMap.intersectionWith(Key)
sedillard <at> gmail.com**20080516174305

 This patch brings the type of IntMap.intersectionWith(Key) in line with that of
 Map.intersectionWith(Key).

 was :: (a->b->a) -> IntMap a -> IntMap b -> IntMap a
 now :: (a->b->c) -> IntMap a -> IntMap b -> IntMap c

 I don't have the test suite but it works fine in GHCi

 *Data.IntMap> intersectionWith (,) (fromList $ zip [1..3] ['a'..'c'])
(fromList $ zip [1..3] ['A'..'C'])
 fromList [(1,('a','A')),(2,('b','B')),(3,('c','C'))]

] {
hunk ./Data/IntMap.hs 795
-intersectionWith :: (a -> b -> a) -> IntMap a -> IntMap b -> IntMap a
+intersectionWith :: (a -> b -> c) -> IntMap a -> IntMap b -> IntMap c
hunk ./Data/IntMap.hs 804
-intersectionWithKey :: (Key -> a -> b -> a) -> IntMap a -> IntMap b -> IntMap a
+intersectionWithKey :: (Key -> a -> b -> c) -> IntMap a -> IntMap b -> IntMap c
}

Context:

The rest of the 67K is context :)

On Fri, May 16, 2008 at 11:28 AM, Don Stewart <dons <at> galois.com> wrote:
> sedillard:

(Continue reading)

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Don Stewart | 16 May 20:07

Re: IntMap intersectionWith type is too restrictive

So a small issue is that we can't apply this patch. Sending
the full patch as an attachment is ok.

sedillard:
> [generalized type of IntMap.intersectionWith(Key)
> sedillard <at> gmail.com**20080516174305
> 
>  This patch brings the type of IntMap.intersectionWith(Key) in line with that of
>  Map.intersectionWith(Key).
> 
>  was :: (a->b->a) -> IntMap a -> IntMap b -> IntMap a
>  now :: (a->b->c) -> IntMap a -> IntMap b -> IntMap c
> 
>  I don't have the test suite but it works fine in GHCi
> 
>  *Data.IntMap> intersectionWith (,) (fromList $ zip [1..3] ['a'..'c'])
> (fromList $ zip [1..3] ['A'..'C'])
>  fromList [(1,('a','A')),(2,('b','B')),(3,('c','C'))]
> 
> 
> ] {
> hunk ./Data/IntMap.hs 795
> -intersectionWith :: (a -> b -> a) -> IntMap a -> IntMap b -> IntMap a
> +intersectionWith :: (a -> b -> c) -> IntMap a -> IntMap b -> IntMap c
> hunk ./Data/IntMap.hs 804
> -intersectionWithKey :: (Key -> a -> b -> a) -> IntMap a -> IntMap b -> IntMap a
> +intersectionWithKey :: (Key -> a -> b -> c) -> IntMap a -> IntMap b -> IntMap c
> }
> 
> Context:

(Continue reading)