combinatorics

v0.1.0

combinatorics v0.1.0 Combinatorics View Source

Utility for generating combinatorics. Extracted from the implementation in CouchDB.

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Functions

binary_combinations(n)

Generate all combinations of true or false for a given number of bits

n_combinations(n, list)

Generate n number of combinations of items in given list

permutations(list)

Generate all permutations of a given list of lists

powerset(list)

Generate a powerset for a given list

product(list)

Generate all product a given list

Link to this section Functions

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binary_combinations(n) View Source 
binary_combinations(pos_integer()) :: [[boolean()]]

Generate all combinations of true or false for a given number of bits.

Returns a list of lists.

Examples 

iex> Combinatorics.binary_combinations(3)
[
   [ false , false , false ],
   [ false , false , true  ],
   [ false , true  , false ],
   [ false , true  , true  ],
   [ true  , false , false ],
   [ true  , false , true  ],
   [ true  , true  , false ],
   [ true  , true  , true  ]
]
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n_combinations(n, list) View Source 
n_combinations(pos_integer(), list()) :: [list()]

Generate n number of combinations of items in given list.

Returns a list of lists with n element.

Examples 

iex> Combinatorics.n_combinations(2, [:mon, :tue, :wed, :thu, :fri])
[
  [:mon, :tue],
  [:mon, :wed],
  [:mon, :thu],
  [:mon, :fri],
  [:tue, :wed],
  [:tue, :thu],
  [:tue, :fri],
  [:wed, :thu],
  [:wed, :fri],
  [:thu, :fri]
]
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permutations(list) View Source 
permutations(list()) :: list()

Generate all permutations of a given list of lists.

Returns a list of lists.

Examples 

iex> Combinatorics.permutations([:foo, :bar, :baz])
[
  [:foo, :bar, :baz],
  [:foo, :baz, :bar],
  [:bar, :foo, :baz],
  [:bar, :baz, :foo],
  [:baz, :foo, :bar],
  [:baz, :bar, :foo]
]
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powerset(list) View Source 
powerset(list()) :: [list()]

Generate a powerset for a given list.

Returns a list.

Examples 

iex> Combinatorics.powerset([:foo, :bar, :baz])
[
    [:foo],
    [:foo,:baz],
    [:foo,:bar,:baz],
    [:foo,:bar],
    [:bar],
    [:bar,:baz],
    [:baz],
    []
]
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product(list) View Source 
product([list()]) :: [list()]

Generate all product a given list.

Returns a list.

Examples 

iex> Combinatorics.product([ [:foo, :bar], [1, 2, 3] ])
[
  [:foo, 1],
  [:foo, 2],
  [:foo, 3],
  [:bar, 1],
  [:bar, 2],
  [:bar, 3]
]