The List Monad

monad.types.list - The List Monad.

class monad.types.list.List(*items)

Bases: monad.types.monadplus.MonadPlus, monad.mixins.Ord, _abcoll.Sequence

The List Monad.

Representing nondeterministic computation.

>>> List(42)
List(42)
>>> List(1, 2, 3)
List(1, 2, 3)
>>> List([])
List([])
>>> List.from_iterable(range(3))
List(0, 1, 2)
>>> List.from_iterable(n for n in (1, 2, 3) if n % 2 == 0)
List(2)
>>> List(List(2))
List(List(2))

Lists are lazy

>>> from itertools import count
>>> m = List.from_iterable(count())
>>> m[:5]
List(0, 1, 2, 3, 4)
>>> m[520:524]
List(520, 521, 522, 523)
>>> list(m[1000:1002])
[1000, 1001]

Bind operation with >>

>>> spawn = lambda cell: List(cell, cell)
>>> spawn('c')
List('c', 'c')
>>> spawn('c') >> spawn
List('c', 'c', 'c', 'c')
>>> grow = lambda cell: List(cell + '~')
>>> grow('o')
List('o~')
>>> grow('o') >> grow >> grow >> grow
List('o~~~~')
>>> generation = lambda cell: grow(cell) + spawn(cell)
>>> first = List('o')
>>> first
List('o')
>>> first >> generation
List('o~', 'o', 'o')
>>> first >> generation >> generation
List('o~~', 'o~', 'o~', 'o~', 'o', 'o', 'o~', 'o', 'o')

fmap(function)

fmap of List Monad.

classmethod from_iterable(iterator)

Creates List from iterable.

join()

join of List Monad.

plus(monad)

plus operation, concatenates two List.