Map a given function onto a set and union the resulting set.

import Set exposing (Set)


neighbors : (Int, Int) -> Set (Int, Int)
neighbors (x, y) =
    Set.fromList
        [ (x - 1, y - 1), (x, y - 1), (x + 1, y - 1)
        , (x - 1, y),                 (x + 1, y)
        , (x - 1, y + 1), (x, y + 1), (x + 1, y + 1)
        ]


setOfPoints : Set (Int, Int)
setOfPoints =
    Set.fromList [(1,1), (0,0)]


Set.Extra.concatMap neighbors setOfPoints
--> Set.fromList
-->     [ (-1,-1), (-1,0), (-1,1)
-->     , (0,-1), (0,0), (0,1)
-->     , (0,2), (1,-1), (1,0)
-->     , (1,1), (1,2), (2,0)
-->     , (2,1), (2,2)
-->     ]

Apply a function that may succeed to all values in the set, but only keep the successes.

import Set exposing (Set)


Set.fromList ["1", "2", "a", "3"]
    |> Set.Extra.filterMap String.toFloat
--> Set.fromList [1, 2, 3]

Check if a Set is a subset of another Set.

import Set exposing (Set)


Set.Extra.subset
    (Set.fromList [1,2,3])
    (Set.fromList [1,2,3,4,5])
--> True

If the set does not contain the element, add it. If it does contain the element, remove it.

import Set exposing (Set)


Set.Extra.toggle 1 (Set.fromList [1,2,3])
--> Set.fromList [2, 3]


Set.Extra.toggle 1 (Set.fromList [2,3])
--> Set.fromList [1, 2, 3]