source: utilitiespy/tudelft/utilities/immutablelist/PowerSet.py@ 1237

from typing import TypeVar
from tudelft.utilities.immutablelist.AbstractImmutableList import AbstractImmutableList
from tudelft.utilities.immutablelist.ImmutableList import ImmutableList
from tudelft.utilities.immutablelist.SubList import SubList
T=TypeVar("T")

class PowerSet(AbstractImmutableList[ImmutableList[T]]):
        '''
        the power set (or powerset) of any set S is the set of all subsets of S,
        including the empty set and S itself. The given list is assumed to be a set,
        so without duplicates.
        
        @param T the element type of all lists that we receive.
        '''


        def __init__(self, lst:ImmutableList[T] ) :
                self._lst = lst

        def get(self, index:int) -> ImmutableList[T] :
                if index >= self.size():
                        raise IndexError("Index out of bounds:" + str(index))
                return SubList[T](self._lst, index)

        def size(self)->int:
                return 1 << self._lst.size()

        def __hash__(self):
                return 17*hash(self._lst)


        def __eq__(self, other):
                return isinstance(other, self.__class__) \
                        and self._lst==other._lst