Semialign

https://hackage.haskell.org/package/semialign-1.4/docs
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Semialign is a Haskell library that provides type classes for aligning and zipping functors with...
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### Non-holding Distributivity Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

An example of a law that does not hold for zip and align.

```haskell
distrThesePair <$> align (zip xs ys) zs ≢ zip (align xs zs) (align ys zs)
```

--------------------------------

### Achieving Legacy Unalign Behavior

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Demonstrates how to replicate the version 1 behavior of unalign using unzipWith.

```haskell
>>> **unzipWith (unalign . Just) [This 'a', That 'b', These 'c' 'd']
**([Just 'a',Nothing,Just 'c'],[Nothing,Just 'b',Just 'd'])
```

--------------------------------

### Zip Instance Methods

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Standard zip and zipWith methods defined for various data types.

```haskell
zip :: ZipList a -> ZipList b -> ZipList (a, b)
zipWith :: (a -> b -> c) -> ZipList a -> ZipList b -> ZipList c
```

```haskell
zip :: Identity a -> Identity b -> Identity (a, b)
zipWith :: (a -> b -> c) -> Identity a -> Identity b -> Identity c
```

```haskell
zip :: NonEmpty a -> NonEmpty b -> NonEmpty (a, b)
zipWith :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c
```

```haskell
zip :: IntMap a -> IntMap b -> IntMap (a, b)
zipWith :: (a -> b -> c) -> IntMap a -> IntMap b -> IntMap c
```

```haskell
zip :: Seq a -> Seq b -> Seq (a, b)
zipWith :: (a -> b -> c) -> Seq a -> Seq b -> Seq c
```

```haskell
zip :: Tree a -> Tree b -> Tree (a, b)
zipWith :: (a -> b -> c) -> Tree a -> Tree b -> Tree c
```

```haskell
zip :: Vector a -> Vector b -> Vector (a, b)
zipWith :: (a -> b -> c) -> Vector a -> Vector b -> Vector c
```

```haskell
zip :: Maybe a -> Maybe b -> Maybe (a, b)
zipWith :: (a -> b -> c) -> Maybe a -> Maybe b -> Maybe c
```

```haskell
zip :: [a] -> [b] -> [(a, b)]
zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
```

```haskell
zip :: Proxy a -> Proxy b -> Proxy (a, b)
zipWith :: (a -> b -> c) -> Proxy a -> Proxy b -> Proxy c
```

```haskell
zip :: Map k a -> Map k b -> Map k (a, b)
zipWith :: (a -> b -> c) -> Map k a -> Map k b -> Map k c
```

```haskell
zip :: HashMap k a -> HashMap k b -> HashMap k (a, b)
zipWith :: (a -> b -> c) -> HashMap k a -> HashMap k b -> HashMap k c
```

```haskell
zip :: Stream m a -> Stream m b -> Stream m (a, b)
zipWith :: (a -> b -> c) -> Stream m a -> Stream m b -> Stream m c
```

```haskell
zip :: Tagged b a -> Tagged b b0 -> Tagged b (a, b0)
zipWith :: (a -> b0 -> c) -> Tagged b a -> Tagged b b0 -> Tagged b c
```

```haskell
zip :: Bundle m v a -> Bundle m v b -> Bundle m v (a, b)
zipWith :: (a -> b -> c) -> Bundle m v a -> Bundle m v b -> Bundle m v c
```

```haskell
zip :: Product f g a -> Product f g b -> Product f g (a, b)
zipWith :: (a -> b -> c) -> Product f g a -> Product f g b -> Product f g c
```

```haskell
zip :: (e -> a) -> (e -> b) -> e -> (a, b)
zipWith :: (a -> b -> c) -> (e -> a) -> (e -> b) -> e -> c
```

```haskell
zip :: Compose f g a -> Compose f g b -> Compose f g (a, b)
zipWith :: (a -> b -> c) -> Compose f g a -> Compose f g b -> Compose f g c
```

--------------------------------

### Zip With Definition

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the relationship between zipWith and zip.

```haskell
zipWith f a b ≡ f <$> zip a b
```

--------------------------------

### Alignment Utility Functions

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Common utility functions for aligning and padding structures.

```Haskell
salign :: (Semialign f, Semigroup a) => f a -> f a -> f a
padZip :: Semialign f => f a -> f b -> f (Maybe a, Maybe b)
padZipWith :: Semialign f => (Maybe a -> Maybe b -> c) -> f a -> f b -> f c
lpadZip :: [a] -> [b] -> [(Maybe a, b)]
lpadZipWith :: (Maybe a -> b -> c) -> [a] -> [b] -> [c]
rpadZip :: [a] -> [b] -> [(a, Maybe b)]
rpadZipWith :: (a -> Maybe b -> c) -> [a] -> [b] -> [c]
alignVectorWith :: (Vector v a, Vector v b, Vector v c) => (These a b -> c) -> v a -> v b -> v c
```

--------------------------------

### Distributivity Laws for Zip and Align

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Laws describing how zip and align interact with pair structures.

```haskell
                   align (zip xs ys) zs ≡ undistrThesePair <$> zip (align xs zs) (align ys zs)
distrPairThese <$> zip (align xs ys) zs ≡                      align (zip xs zs) (zip ys zs)
                   zip (align xs ys) zs ≡ undistrPairThese <$> align (zip xs zs) (zip ys zs)
```

--------------------------------

### Unzip Default Implementation

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

A default implementation of unzip for Functor instances.

```haskell
unzipDefault :: Functor f => f (a, b) -> (f a, f b)
```

--------------------------------

### padZip

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Aligns two structures similar to zip, filling missing values with Nothing.

```APIDOC
## padZip

### Description
Align two structures as in `zip`, but filling in blanks with `Nothing`.

### Signature
`padZip :: Semialign f => f a -> f b -> f (Maybe a, Maybe b)`
```

--------------------------------

### Unzip Typeclass Definition

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

The minimal complete definition and method signatures for the Unzip typeclass.

```haskell
unzipWith :: (c -> (a, b)) -> f c -> (f a, f b)
unzip :: f (a, b) -> (f a, f b)
```

--------------------------------

### zipWith :: (a -> b -> c) -> f a -> f b -> f c

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Combines two structures by taking the intersection of their shapes and combining the elements with the given function.

```APIDOC
## zipWith

### Description
Combines two structures by taking the intersection of their shapes and combining the elements with the given function.

### Signature
zipWith :: (a -> b -> c) -> f a -> f b -> f c
```

--------------------------------

### salign

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Aligns two structures and combines them using the Semigroup operation.

```APIDOC
## salign

### Description
Align two structures and combine with `<>`.

### Signature
`salign :: (Semialign f, Semigroup a) => f a -> f a -> f a`
```

--------------------------------

### padZipWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Aligns two structures similar to zipWith, providing Maybe values to the combining function.

```APIDOC
## padZipWith

### Description
Align two structures as in `zipWith`, but filling in blanks with `Nothing`.

### Signature
`padZipWith :: Semialign f => (Maybe a -> Maybe b -> c) -> f a -> f b -> f c`
```

--------------------------------

### unzip

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Splits a structure of pairs into a pair of structures.

```APIDOC
## unzip

### Description
Takes a structure containing pairs and returns a pair of structures, where the first contains the first elements of the pairs and the second contains the second elements.

### Signature
unzip :: f (a, b) -> (f a, f b)
```

--------------------------------

### Bicrosswalk Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Crosswalk.html

Defines the expected behavior for Bicrosswalk instances.

```haskell
bicrosswalk (const empty) (const empty) = const empty
bicrosswalk f g = bisequenceL . bimap f g
```

--------------------------------

### lpadZipWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Performs a left-padded zipWith operation on lists.

```APIDOC
## lpadZipWith

### Description
Left-padded `zipWith`.

### Signature
`lpadZipWith :: (Maybe a -> b -> c) -> [a] -> [b] -> [c]`
```

--------------------------------

### rpadZipWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Performs a right-padded zipWith operation on lists.

```APIDOC
## rpadZipWith

### Description
Right-padded `zipWith`.

### Signature
`rpadZipWith :: (a -> Maybe b -> c) -> [a] -> [b] -> [c]`
```

--------------------------------

### RepeatWithIndex

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign-Indexed.html

The RepeatWithIndex type-class allows for the creation of structures where elements are generated based on their index.

```APIDOC
## class RepeatWithIndex i f

### Description
Provides the `irepeat` method to generate a structure where each element is determined by a function of its index.

### Methods
- **irepeat** :: (i -> a) -> f a
  - Generates a structure `f a` where each element at index `i` is produced by the provided function.
```

--------------------------------

### alignWith :: (These a b -> c) -> f a -> f b -> f c

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Combines two structures by taking the union of their shapes and combining the elements with the given function.

```APIDOC
## alignWith

### Description
Analogous to zipWith, combines two structures by taking the union of their shapes and combining the elements with the given function.

### Signature
alignWith :: (These a b -> c) -> f a -> f b -> f c
```

--------------------------------

### With Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the relationship between alignWith and align.

```haskell
alignWith f a b ≡ f <$> align a b
```

--------------------------------

### lpadZip

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Performs a left-padded zip operation on lists.

```APIDOC
## lpadZip

### Description
Left-padded `zip`.

### Signature
`lpadZip :: [a] -> [b] -> [(Maybe a, b)]`
```

--------------------------------

### zip :: f a -> f b -> f (a, b)

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Combines two structures by taking the intersection of their shapes and using a pair to hold the elements.

```APIDOC
## zip

### Description
Combines two structures by taking the intersection of their shapes and using pair to hold the elements.

### Signature
zip :: f a -> f b -> f (a, b)
```

--------------------------------

### Align and Unalign Type-classes

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Extends Semialign with nil and unalign operations.

```Haskell
class Semialign f => Align (f :: Type -> Type) where
    nil :: f a
class Semialign f => Unalign (f :: Type -> Type) where
    unalign :: f (These a b) -> (f a, f b)
    unalignWith :: (c -> These a b) -> f c -> (f a, f b)
```

--------------------------------

### align :: f a -> f b -> f (These a b)

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Combines two structures by taking the union of their shapes and using These to hold the elements.

```APIDOC
## align

### Description
Analogous to zip, combines two structures by taking the union of their shapes and using These to hold the elements.

### Signature
align :: f a -> f b -> f (These a b)
```

--------------------------------

### rpadZip

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Performs a right-padded zip operation on lists.

```APIDOC
## rpadZip

### Description
Right-padded `zip`.

### Signature
`rpadZip :: [a] -> [b] -> [(a, Maybe b)]`
```

--------------------------------

### Unzip Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the expected behavior for unzip operations, noting that behavior may differ between sequence-like and map-like types.

```haskell
uncurry zip (unzip xs) ≡ xs
unzip (zip xs xs) ≡ (xs, (xs))
```

```haskell
unzip (zip xs ys) ≢ (xs, _) or (_, ys)
```

--------------------------------

### Crosswalk Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Crosswalk.html

Defines the expected behavior for Crosswalk instances.

```haskell
crosswalk (const nil) = const nil
crosswalk f = sequenceL . fmap f
```

--------------------------------

### Unzip Typeclass Methods

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

The Unzip typeclass defines methods for decomposing structures containing pairs. Users can implement these for custom types to enable splitting functionality.

```APIDOC
## unzipWith :: (c -> (a, b)) -> f c -> (f a, f b)

### Description
Maps each element of the structure to a pair, then splits the structure into two separate structures.

## unzip :: f (a, b) -> (f a, f b)

### Description
Splits a structure of pairs into a pair of structures.
```

--------------------------------

### Functoriality Law for Zip

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the relationship between mapping functions over structures and the zip operation.

```haskell
zip (f <$> x) (g <$> y) ≡ bimap f g <$> zip x y
```

--------------------------------

### ZipWithIndex

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign-Indexed.html

The ZipWithIndex type-class provides an indexed version of Zip, allowing for zipping operations that utilize the index of the elements.

```APIDOC
## class ZipWithIndex i f

### Description
An indexed version of the Zip type-class. It provides the `izipWith` method to zip two structures while providing the index to the combining function.

### Methods
- **izipWith** :: (i -> a -> b -> c) -> f a -> f b -> f c
  - Analogous to `zipWith`, but also provides an index `i` to the combining function.
```

--------------------------------

### Repeat Class Definition and Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the Repeat class for zippable functors and its associated laws.

```haskell
class Zip f => Repeat (f :: Type -> Type) where
```

```haskell
fst <$> zip xs (repeat y) ≡ xs
snd <$> zip (repeat x) ys ≡ ys
```

```haskell
repeat :: a -> f a
```

--------------------------------

### unzipWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Splits a structure of values into a pair of structures by applying a function to each element.

```APIDOC
## unzipWith

### Description
Applies a function to each element in a structure to produce a pair, then splits the structure into two separate structures.

### Signature
unzipWith :: (c -> (a, b)) -> f c -> (f a, f b)
```

--------------------------------

### Zippy Newtype

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Definition of the Zippy newtype wrapper.

```haskell
newtype Zippy (f :: Type -> Type) a
```

--------------------------------

### Zip Associativity Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the associativity law for the Zip operation.

```haskell
zip x (zip y z) ≡ assoc <$> zip (zip x y) z
```

--------------------------------

### unalignWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Maps a function over a structure and then unaligns the result.

```APIDOC
## unalignWith

### Description
Applies a function `(c -> These a b)` to elements of a structure `f c` and returns a pair of structures `(f a, f b)`.

### Signature
`unalignWith :: (c -> These a b) -> f c -> (f a, f b)`
```

--------------------------------

### unalign

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Splits a structure of 'These a b' values into a pair of structures containing 'a' and 'b' values respectively.

```APIDOC
## unalign

### Description
Takes a structure `f` containing `These a b` values and returns a pair of structures `(f a, f b)`.

### Signature
`unalign :: f (These a b) -> (f a, f b)`
```

--------------------------------

### Semialign Type-class Definition

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the core Semialign type-class for functors supporting union-based alignment.

```Haskell
class Unzip f => Semialign (f :: Type -> Type) where
    align :: f a -> f b -> f (These a b)
    alignWith :: (These a b -> c) -> f a -> f b -> f c
```

--------------------------------

### SemialignWithIndex

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign-Indexed.html

The SemialignWithIndex type-class provides an indexed version of Semialign, allowing for alignment operations that utilize the index of the elements.

```APIDOC
## class SemialignWithIndex i f

### Description
An indexed version of the Semialign type-class. It provides the `ialignWith` method to align two structures while providing the index to the combining function.

### Methods
- **ialignWith** :: (i -> These a b -> c) -> f a -> f b -> f c
  - Analogous to `alignWith`, but also provides an index `i` to the combining function.
```

--------------------------------

### Zip Commutativity Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the commutativity law for the Zip operation.

```haskell
zip x y ≡ swap <$> zip y x
```

--------------------------------

### Zippyness Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Identities relating zip to fst and snd projections.

```haskell
fmap fst (zip x x) ≡ x
fmap snd (zip x x) ≡ x
zip (fmap fst x) (fmap snd x) ≡ x
```

--------------------------------

### Unalign Algebraic Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the primary law for unalign operations.

```haskell
unalign (align xs ys) ≡ (xs, ys)
```

--------------------------------

### Zip Idempotency Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the idempotency law for the Zip operation.

```haskell
join zip   ≡ fmap (join (,))
```

--------------------------------

### Align Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the identity laws for the align operation when combined with an empty structure.

```haskell
(`align` nil) ≡ fmap This
(nil `align`) ≡ fmap That
```

--------------------------------

### Zip Absorption Laws

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Zip.html

Defines the absorption laws relating Zip and Align operations.

```haskell
fst    <$> zip xs (align xs ys) ≡ xs
toThis <$> align xs (zip xs ys) ≡ This <$> xs
  where
    toThis (This a)    = This a
    toThis (These a _) = This a
    toThis (That b)    = That b
```

--------------------------------

### Repeat Typeclass Definition

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

The Repeat typeclass defines structures that support left and right units for zipping.

```haskell
fst <$> zip xs (repeat y) ≡ xs
snd <$> zip (repeat x) ys ≡ ys
```

```haskell
class Zip f => Repeat (f :: Type -> Type) where
repeat :: a -> f a
```

--------------------------------

### alignVectorWith

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Semialign.html

Aligns two vectors using a combining function.

```APIDOC
## alignVectorWith

### Description
Aligns two vectors using the provided function.

### Signature
`alignVectorWith :: (Vector v a, Vector v b, Vector v c) => (These a b -> c) -> v a -> v b -> v c`
```

--------------------------------

### Historical Unalign Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

The right inverse law that was removed in version 1.4 to support list-like instances.

```haskell
uncurry align (unalign xs) ≡ xs
```

--------------------------------

### Idempotency Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the idempotency property for the align operation.

```haskell
join align ≡ fmap (join These)
```

--------------------------------

### Alignedness Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the alignedness property for Foldable structures.

```haskell
toList x ≡ toListOf (folded . here) (align x y)
         ≡ mapMaybe justHere (toList (align x y))
```

--------------------------------

### Associativity Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the associativity property for the align operation.

```haskell
align x (align y z) ≡ assoc <$> align (align x y) z
```

--------------------------------

### Commutativity Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the commutativity property for the align operation.

```haskell
align x y ≡ swap <$> align y x
```

--------------------------------

### Functoriality Law

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the functoriality property for the align operation.

```haskell
align (f <$> x) (g <$> y) ≡ bimap f g <$> align x y
```

--------------------------------

### Unalign Type Class Definition

Source: https://hackage.haskell.org/package/semialign-1.4/docs/Data-Align.html

Defines the Unalign class for functors that support splitting a union shape into component parts.

```haskell
class Semialign f => Unalign (f :: Type -> Type) where
```
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