Takes a key-fn and a list. Creates a Dict which maps the key to a list of matching elements.

import AssocList as Dict


groupBy String.length [ "tree" , "apple" , "leaf" ]
--> Dict.fromList [ ( 4, [ "tree", "leaf" ] ), ( 5, [ "apple" ] ) ]

Takes a key-fn and a list. Creates a Dict which maps the key to a list of matching elements, skipping elements where key-fn returns Nothing

import AssocList as Dict


filterGroupBy (String.uncons >> Maybe.map Tuple.first) [ "tree" , "", "tweet", "apple" , "leaf", "" ]
--> Dict.fromList [ ( 't', [ "tree", "tweet" ] ), ( 'a', [ "apple" ] ), ( 'l', [ "leaf" ] ) ]


filterGroupBy
    .car
    [ { name = "Mary"
      , car = Just "Ford"
      }
    , { name = "Jack"
      , car = Nothing
      }
    , { name = "Jill"
      , car = Just "Tesla"
      }
    , { name = "John"
      , car = Just "Tesla"
      }
    ]
--> Dict.fromList
--> [ ( "Ford"
-->   , [ { name = "Mary" , car = Just "Ford" } ]
-->   )
--> , ( "Tesla"
-->   , [ { name = "Jill" , car = Just "Tesla" }
-->     , { name = "John" , car = Just "Tesla" }
-->     ]
-->   )
--> ]

Create a dictionary from a list of values, by passing a function that can get a key from any such value. If the function does not return unique keys, earlier values are discarded.

import AssocList as Dict


fromListBy String.length [ "tree" , "apple" , "leaf" ]
--> Dict.fromList [ ( 4, "leaf" ), ( 5, "apple" ) ]

Like Dict.fromList, but you provide a way to deal with duplicate keys. Create a dictionary from a list of pairs of keys and values, providing a function that is used to combine multiple values paired with the same key.

import AssocList as Dict


fromListDedupe
    (\a b -> a ++ " " ++ b)
    [ ( "class", "menu" ), ( "width", "100%" ), ( "class", "big" ) ]
--> Dict.fromList [ ( "class", "menu big" ), ( "width", "100%" ) ]

fromListBy and fromListDedupe rolled into one.

import AssocList as Dict


fromListDedupeBy (\first second -> first) String.length [ "tree" , "apple" , "leaf" ]
--> Dict.fromList [ ( 4, "tree" ), ( 5, "apple" ) ]

Count the number of occurences for each of the elements in the list.

import AssocList as Dict


frequencies [ "A", "B", "C", "B", "C", "B" ]
--> Dict.fromList [ ( "A", 1 ), ( "B", 3 ), ( "C", 2 ) ]

Remove elements which satisfies the predicate.

import AssocList as Dict


Dict.fromList [ ( "Mary", 1 ), ( "Jack", 2 ), ( "Jill", 1 ) ]
    |> removeWhen (\_ value -> value == 1 )
--> Dict.fromList [ ( "Jack", 2 ) ]

Remove a key-value pair if its key appears in the set.

import AssocList as Dict
import AssocSet as Set


Dict.fromList [ ( "Mary", 1 ), ( "Jack", 2 ), ( "Jill", 1 ) ]
    |> removeMany (Set.fromList [ "Mary", "Jill" ])
--> Dict.fromList [ ( "Jack", 2 ) ]

Keep a key-value pair if its key appears in the set.

import AssocList as Dict
import AssocSet as Set


Dict.fromList [ ( "Mary", 1 ), ( "Jack", 2 ), ( "Jill", 1 ) ]
    |> keepOnly (Set.fromList [ "Jack", "Jill" ])
--> Dict.fromList [ ( "Jack", 2 ), ( "Jill", 1 ) ]

Insert an element at the given key, providing a combining function that used in the case that there is already an element at that key. The combining function is called with original element and the new element as arguments and returns the element to be inserted.

import AssocList as Dict


Dict.fromList [ ( "expenses", 38.25 ), ( "assets", 100.85 ) ]
    |> insertDedupe (+) "expenses" 2.50
    |> insertDedupe (+) "liabilities" -2.50
--> Dict.fromList [ ( "expenses", 40.75 ), ( "assets", 100.85 ), ( "liabilities", -2.50 ) ]

Apply a function to all keys in a dictionary.

import AssocList as Dict


Dict.fromList [ ( 5, "Jack" ), ( 10, "Jill" ) ]
    |> mapKeys (\x -> x + 1)
--> Dict.fromList [ ( 6, "Jack" ), ( 11, "Jill" ) ]


Dict.fromList [ ( 5, "Jack" ), ( 10, "Jill" ) ]
    |> mapKeys String.fromInt
--> Dict.fromList [ ( "5", "Jack" ), ( "10", "Jill" ) ]

Apply a function that may or may not succeed to all entries in a dictionary, but only keep the successes.

import AssocList as Dict


let
    isTeen n a =
        if 13 <= n && n <= 19 then
            Just <| String.toUpper a
        else
            Nothing
in
Dict.fromList [ ( 5, "Jack" ), ( 15, "Jill" ), ( 20, "Jones" ) ]
    |> filterMap isTeen
--> Dict.fromList [ ( 15, "JILL" ) ]

Inverts the keys and values of an array.

import AssocList as Dict


Dict.fromList [ ("key", "value")  ]
    |> invert
--> Dict.fromList [ ( "value", "key" ) ]

Determine if any key/value pair satisfies some test.

import AssocList as Dict


Dict.fromList [ ( 9, "Jill" ), ( 7, "Jill" ) ]
    |> any (\_ value -> value == "Jill")
--> True


Dict.fromList [ ( 9, "Jill" ), ( 7, "Jill" ) ]
    |> any (\key _ -> key == 5)
--> False

Find the first key/value pair that matches a predicate.

import AssocList as Dict


Dict.fromList [ ( 9, "Jill" ), ( 7, "Jill" ) ]
    |> find (\_ value -> value == "Jill")
--> Just ( 7, "Jill" )


Dict.fromList [ ( 9, "Jill" ), ( 7, "Jill" ) ]
    |> find (\key _ -> key == 5)
--> Nothing