agtest/main.py

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2021-06-09 00:56:30 +00:00
from typing import Generic, TypeVar, Optional, Callable
T = TypeVar("T")
class Thunk(Generic[T]):
value: Optional[T]
def __init__(self, func: Callable[[], T]):
self.func = func
self.value = None
def get(self) -> T:
if self.value is None:
self.value = self.func()
return self.value
class Node:
value: Thunk[int]
class Add(Node):
def __init__(self, left: Node, right: Node):
self.value = Thunk(lambda: left.value.get() + right.value.get())
class Mul(Node):
def __init__(self, left: Node, right: Node):
self.value = Thunk(lambda: left.value.get() * right.value.get())
class Lit(Node):
def __init__(self, num: int):
self.num = num
self.value = Thunk(lambda: num)
if __name__ == "__main__":
tree = Add(Mul(Lit(3), Lit(4)), Lit(5))
print(tree.value.get())