type-fun-0.0.1: Collection of widely reimplemented type families

Safe HaskellNone




Collection of type families on type lists. This module differs from Data.Singletons.Prelude.List because works with [*] and relies on GHC's type equality (~). The rest of required operations like Reverse or '(:++:)' you could find in singletons


Primitive operations on lists

type family Length a :: N Source


Length `[]` = Z 
Length (a : as) = S (Length as) 

type family Drop c s :: [k] Source


Drop Z s = s 
Drop (S c) `[]` = `[]` 
Drop (S c) (a : as) = Drop c as 

type family Take c s :: [k] Source


Take Z s = `[]` 
Take (S c) `[]` = `[]` 
Take (S c) (a : as) = a : Take c as 

type family Delete a s :: [k] Source

Remove first argument type from anywhere in a list.


Delete a `[]` = `[]` 
Delete a (a : as) = Delete a as 
Delete a (b : as) = b : Delete a as 

type family Remove i a :: [k] Source

Remove index from the list


Remove i `[]` = `[]` 
Remove Z (a : as) = as 
Remove (S i) (a : as) = a : Remove i as 

type family a :++: b :: [k] Source


`[]` :++: b = b 
(a : as) :++: b = a : (as :++: b) 

Elements lookup

type family IndexOfMay' acc a s :: Maybe N Source


IndexOfMay' acc a `[]` = Nothing 
IndexOfMay' acc a (a : as) = Just acc 
IndexOfMay' acc a (b : as) = IndexOfMay' (S acc) a as 

type family IndicesOfMay a b :: [Maybe N] Source


IndicesOfMay `[]` bs = `[]` 
IndicesOfMay (a : as) bs = IndexOfMay a bs : IndicesOfMay as bs 

type family IndicesOf a b :: [N] Source


IndicesOf `[]` bs = `[]` 
IndicesOf (a : as) bs = IndexOf a bs : IndicesOf as bs 

type Index idx s = FromJust (IndexMay idx s) Source

type family IndexMay idx s :: Maybe k Source


IndexMay idx `[]` = Nothing 
IndexMay Z (a : as) = Just a 
IndexMay (S idx) (a : as) = IndexMay idx as 

type family IndicesMay idxs a :: [Maybe k] Source


IndicesMay `[]` as = `[]` 
IndicesMay (i : idxs) as = IndexMay i as : IndicesMay idxs as 

type family Indices idxs a :: [k] Source


Indices `[]` as = `[]` 
Indices (i : idxs) as = Index i as : Indices idxs as 

type Elem a s = NothingToConstr (IndexOfMay a s) (ElementNotFoundInList a s) Source

Generates unresolvable constraint if fists element is not contained inside of second

type NotElem a s = JustToConstr (IndexOfMay a s) (ElementIsInList a s) Source

Reverse of Elem

type family Count a s :: N Source

Count elements in a list


Count a `[]` = Z 
Count a (a : as) = S (Count a as) 
Count a (b : as) = Count a as 

Operations with lists

type family SubList a b :: Constraint Source

Constanints that first argument is a sublist of second. Reduces to (Elem a1 b, Elem a2 b, Elem a3 b, ...)


SubList `[]` bs = () 
SubList (a : as) bs = (Elem a bs, SubList as bs) 

type family NotSubList a b :: Constraint Source


NotSubList `[]` bs = () 
NotSubList (a : as) bs = (NotElem a bs, NotSubList as bs) 

type IsPrefixOf a b = (If (IsPrefixOfBool a b) (() :: Constraint) (ListIsNotPrefixOf a b), SubList a b) Source

type IsNotPrefixOf a b = If (IsPrefixOfBool a b) (ListIsPrefixOf a b) (() :: Constraint) Source

type family IsPrefixOfBool a b :: Bool Source

First argument is prefix of second


IsPrefixOfBool `[]` b = True 
IsPrefixOfBool (a : as) (a : bs) = IsPrefixOfBool as bs 
IsPrefixOfBool as bs = False 

Set operations

type family Union a b :: [k] Source

Appends elements from first list to second if they are not presented in.


Union `[]` bs = bs 
Union (a : as) bs = Union as (AppendUniq a bs) 

type family UnionList l :: [k] Source


UnionList `[]` = `[]` 
UnionList (a : as) = Union a (UnionList as) 

type family AppendUniq a s :: [k] Source

Append element to list if element is not already presented in


AppendUniq a (a : bs) = a : bs 
AppendUniq a (b : bs) = b : AppendUniq a bs 
AppendUniq a `[]` = `[a]` 

type Intersect a b = Indices (CatMaybes (IndicesOfMay a b)) b Source

Calculates intersection between two lists. Order of elements is taken from first list

Uniqueness checking

type ElementIsUniq a s = If (Equal (S Z) (Count a s)) (() :: Constraint) (ElementIsNotUniqInList a s) Source

Checks that element a occurs in a list just once

type UniqElements a = UniqElements' a a Source

Checks that all elements in list are unique

type family UniqElements' a self :: Constraint Source


UniqElements' `[]` self = () 
UniqElements' (a : as) self = (ElementIsUniq a self, UniqElements' as self)