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import abc
import dataclasses
from typing import Callable, Tuple, TypeVar, Generic
class StateCacheMixin(abc.ABC):
@property
@abc.abstractmethod
def cache(self) -> dict:
...
State = TypeVar('State', bound=StateCacheMixin)
U = TypeVar('U')
V = TypeVar('V')
class StateMonadMixin(
Generic[State, U],
abc.ABC,
):
@property
@abc.abstractmethod
def apply_func(self) -> Callable[[State], tuple[State, U]]:
...
def map(self, fn: Callable[[U], V]) -> 'StateMonadMixin[State, V]':
def internal_map(state: State) -> Tuple[State, U]:
n_state, val = self.apply(state)
return n_state, fn(val)
return dataclasses.replace(self, apply_func=internal_map)
def flat_map(self, fn: Callable[[U], 'StateMonadMixin']) -> 'StateMonadMixin[State, V]':
def internal_map(state: State) -> Tuple[State, V]:
n_state, val = self.apply(state)
return fn(val).apply(n_state)
return dataclasses.replace(self, apply_func=internal_map)
def zip(self, other: 'StateMonadMixin') -> 'StateMonadMixin':
def internal_map(state: State) -> Tuple[State, V]:
state, val1 = self.apply(state)
state, val2 = other.apply(state)
return state, (val1, val2)
return dataclasses.replace(self, apply_func=internal_map)
def cache(self) -> 'StateMonadMixin':
def internal_map(state: State) -> Tuple[State, V]:
if self in state.cache:
return state, state.cache[self]
state, val = self.apply(state)
state = dataclasses.replace(
state,
cache=state.cache | {self: val},
)
return state, val
return dataclasses.replace(self, apply_func=internal_map)
def apply(self, state: State) -> Tuple[State, U]:
return self.apply_func(state)
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