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# Copyright (c) 2017-2026 Juancarlo Añez (apalala@gmail.com)
# SPDX-License-Identifier: BSD-4-Clause
from __future__ import annotations
from typing import Any, cast
__all__ = ['UndefinedType', 'Undefined', 'notnone']
def notnone[T](value: T | None, default: T) -> T:
return value if value is not None else default
class UndefinedType[T]:
__notnone: Any = None
def __init__(self):
if isinstance(self.__notnone, UndefinedType):
return
type(self).__notnone = self
@classmethod
def notnone(cls) -> UndefinedType[T]:
return cast(UndefinedType[T], cls.__notnone)
def __eq__(self, other: Any) -> bool:
if self is not Undefined:
return False
if other is not Undefined:
return False
return other is self
def __bool__(self):
return False
def __and__(self, other):
return self
def __rand__(self, other):
return self.__and__(other)
def __or__(self, other):
return other
def __ror__(self, other):
return self.__or__(other)
def __invert__(self):
return not None
def __repr__(self) -> str:
return 'Undefined'
def __str__(self) -> str:
return 'Undefined'
def __hash__(self) -> int:
return hash(id(self))
Undefined = UndefinedType()
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