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  1. keysSet :: HashMap k a -> HashSet k

    unordered-containers Data.HashMap.Strict

    Produce a HashSet of all the keys in the given HashMap. 

    >>> HashSet.keysSet (HashMap.fromList [(1, "a"), (2, "b")]
fromList [1,2]

  2. module Data.HashSet

    Introduction

    HashSet allows you to store unique elements, providing efficient insertion, lookups, and deletion. A HashSet makes no guarantees as to the order of its elements. If you are storing sets of Data.Ints consider using Data.IntSet from the containers package.

    Examples

    All the examples below assume HashSet is imported qualified, and uses the following dataStructures set. 
    >>> import qualified Data.HashSet as HashSet

>>> let dataStructures = HashSet.fromList ["Set", "Map", "Graph", "Sequence"]

    Basic Operations

    Check membership in a set: 
    >>> -- Check if "Map" and "Trie" are in the set of data structures.

>>> HashSet.member "Map" dataStructures
True

>>> HashSet.member "Trie" dataStructures
False
    Add a new entry to the set: 
    >>> let moreDataStructures = HashSet.insert "Trie" dataStructures

>>> HashSet.member "Trie" moreDataStructures
> True
    Remove the "Graph" entry from the set of data structures. 
    >>> let fewerDataStructures = HashSet.delete "Graph" dataStructures

>>> HashSet.toList fewerDataStructures
["Map","Set","Sequence"]
    Create a new set and combine it with our original set. 
    >>> let unorderedDataStructures = HashSet.fromList ["HashSet", "HashMap"]

>>> HashSet.union dataStructures unorderedDataStructures
fromList ["Map","HashSet","Graph","HashMap","Set","Sequence"]

    Using custom data with HashSet

    To create a HashSet of your custom type, the type must have instances for Eq and Hashable. The Hashable typeclass is defined in the hashable package, see the documentation for information on how to make your type an instance of Hashable. We'll start by setting up our custom data type: 
    >>> :set -XDeriveGeneric

>>> import GHC.Generics (Generic)

>>> import Data.Hashable

>>> data Person = Person { name :: String, likesDogs :: Bool } deriving (Show, Eq, Generic)

>>> instance Hashable Person
    And now we'll use it! 
    >>> let people = HashSet.fromList [Person "Lana" True, Person "Joe" False, Person "Simon" True]

>>> HashSet.filter likesDogs people
fromList [Person {name = "Simon", likesDogs = True},Person {name = "Lana", likesDogs = True}]

    Performance

    The implementation is based on hash array mapped tries. A HashSet is often faster than other Ord-based set types, especially when value comparisons are expensive, as in the case of strings. Many operations have a average-case complexity of <math>. The implementation uses a large base (i.e. 16) so in practice these operations are constant time.

  3. data HashSet a

    unordered-containers Data.HashSet

    A set of values. A set cannot contain duplicate values.

  4. isSubsetOf :: (Eq a, Hashable a) => HashSet a -> HashSet a -> Bool

    unordered-containers Data.HashSet

    Inclusion of sets.

    Examples

    >>> fromList [1,3] `isSubsetOf` fromList [1,2,3]
True

    >>> fromList [1,2] `isSubsetOf` fromList [1,3]
False

  5. newtype HashSet a

    unordered-containers Data.HashSet.Internal

    A set of values. A set cannot contain duplicate values.

  6. HashSet :: HashMap a () -> HashSet a

    unordered-containers Data.HashSet.Internal

    No documentation available.

  7. isSubsetOf :: (Eq a, Hashable a) => HashSet a -> HashSet a -> Bool

    unordered-containers Data.HashSet.Internal

    Inclusion of sets.

    Examples

    >>> fromList [1,3] `isSubsetOf` fromList [1,2,3]
True

    >>> fromList [1,2] `isSubsetOf` fromList [1,3]
False

  8. keysSet :: HashMap k a -> HashSet k

    unordered-containers Data.HashSet.Internal

    Produce a HashSet of all the keys in the given HashMap. 

    >>> HashSet.keysSet (HashMap.fromList [(1, "a"), (2, "b")]
fromList [1,2]

  9. type ByteOffset = Int64

    binary Data.Binary.Get

    An offset, counted in bytes.

  10. parseTest :: Show a => Parser a -> ByteString -> IO ()

    attoparsec Data.Attoparsec.ByteString

    Run a parser and print its result to standard output.

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