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The Zip class from Data.Zip requires an implementation of Semialign: class Semialign f => Zip f In my mind: Zip takes the intersection of two shapes. Semialign takes the union of two sha...
Question
haskell
#2: Post edited
by
WheatWizard
·
2024-02-14T19:48:50Z (10 months ago)
Capitalization
Why does `Zip` require `SemiAlign`
- Why does `Zip` require `Semialign`
The `Zip` class from `Data.Zip` requires an implementation of `SemiAlign`:- ```haskell
class SemiAlign f => Zip f- ```
- In my mind:
- - `Zip` takes the intersection of two shapes.
- `SemiAlign` takes the union of two shapes.- For 2D matrices I can take the intersection of two matrices, but not the union. For example:
- ```
- a :: Array (Int, Int) Int
- a =
- matrix
- [[1,1,1]
- ,[1,1,1]
- ]
- b :: Array (Int, Int) Int
- b =
- matrix
- [[0,2]
- ,[2,0]
- ,[0,2]
- ]
- ```
- I can zip these:
- ```text
- zipWith (+) a b =
- [[1,3]
- ,[3,1]
- ]
- ```
- but their union is not a rectangle, so I can't align them.
But implementing `Zip` on `Array (Int, Int)`, requires first implementing `SemiAlign`.- Why is that? It seems like a totally extraneous requirement.
- The `Zip` class from `Data.Zip` requires an implementation of `Semialign`:
- ```haskell
- class Semialign f => Zip f
- ```
- In my mind:
- - `Zip` takes the intersection of two shapes.
- - `Semialign` takes the union of two shapes.
- For 2D matrices I can take the intersection of two matrices, but not the union. For example:
- ```
- a :: Array (Int, Int) Int
- a =
- matrix
- [[1,1,1]
- ,[1,1,1]
- ]
- b :: Array (Int, Int) Int
- b =
- matrix
- [[0,2]
- ,[2,0]
- ,[0,2]
- ]
- ```
- I can zip these:
- ```text
- zipWith (+) a b =
- [[1,3]
- ,[3,1]
- ]
- ```
- but their union is not a rectangle, so I can't align them.
- But implementing `Zip` on `Array (Int, Int)`, requires first implementing `Semialign`.
- Why is that? It seems like a totally extraneous requirement.
#1: Initial revision
by
WheatWizard
·
2024-02-14T19:48:12Z (10 months ago)
Why does `Zip` require `SemiAlign`
The `Zip` class from `Data.Zip` requires an implementation of `SemiAlign`: ```haskell class SemiAlign f => Zip f ``` In my mind: - `Zip` takes the intersection of two shapes. - `SemiAlign` takes the union of two shapes. For 2D matrices I can take the intersection of two matrices, but not the union. For example: ``` a :: Array (Int, Int) Int a = matrix [[1,1,1] ,[1,1,1] ] b :: Array (Int, Int) Int b = matrix [[0,2] ,[2,0] ,[0,2] ] ``` I can zip these: ```text zipWith (+) a b = [[1,3] ,[3,1] ] ``` but their union is not a rectangle, so I can't align them. But implementing `Zip` on `Array (Int, Int)`, requires first implementing `SemiAlign`. Why is that? It seems like a totally extraneous requirement.