39 lines
1.0 KiB
Python
39 lines
1.0 KiB
Python
"""Parametric polymorphism. Requires Python >= 3.9."""
|
|
|
|
from typing import Callable
|
|
from typing import Generic
|
|
from typing import Iterable
|
|
from typing import TypeVar
|
|
from typing import Union
|
|
|
|
T = TypeVar("T")
|
|
|
|
|
|
class Tree(Generic[T]):
|
|
def __init__(self, value: T):
|
|
self.value = value
|
|
self.left: Union[Tree[T], None] = None
|
|
self.right: Union[Tree[T], None] = None
|
|
|
|
def map(self, func: Callable[[T], T]) -> Iterable[T]:
|
|
yield func(self.value)
|
|
if self.left is not None:
|
|
yield from self.left.map(func)
|
|
if self.right is not None:
|
|
yield from self.right.map(func)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
tree = Tree(7)
|
|
tree.left = Tree(42)
|
|
tree.right = Tree(101)
|
|
tree.right.left = Tree(1)
|
|
|
|
# Fails static type checking as "foo" is not an int.
|
|
# tree.left.left = Tree[int]("foo")
|
|
|
|
# Fails static type checking as Tree[str] is not Tree[int]
|
|
# tree.left.left = Tree("bar")
|
|
|
|
print(list(tree.map(lambda v: v + 1))) # [8, 43, 102, 2]
|