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- # mypy: allow-untyped-defs
- from contextlib import contextmanager
- from .dispatch import dispatch
- from .utils import hashable
- _global_logic_variables = set() # type: ignore[var-annotated]
- _glv = _global_logic_variables
- class Var:
- """Logic Variable"""
- _id = 1
- def __new__(cls, *token):
- if len(token) == 0:
- token = f"_{Var._id}" # type: ignore[assignment]
- Var._id += 1
- elif len(token) == 1:
- token = token[0]
- obj = object.__new__(cls)
- obj.token = token # type: ignore[attr-defined]
- return obj
- def __str__(self):
- return "~" + str(self.token) # type: ignore[attr-defined]
- __repr__ = __str__
- def __eq__(self, other):
- return type(self) is type(other) and self.token == other.token # type: ignore[attr-defined]
- def __hash__(self):
- return hash((type(self), self.token)) # type: ignore[attr-defined]
- def var():
- return lambda *args: Var(*args)
- def vars():
- return lambda n: [var() for i in range(n)]
- @dispatch(Var)
- def isvar(v):
- return True
- isvar
- @dispatch(object) # type: ignore[no-redef]
- def isvar(o):
- return _glv and hashable(o) and o in _glv
- @contextmanager
- def variables(*variables):
- """
- Context manager for logic variables
- Example:
- >>> # xdoctest: +SKIP("undefined vars")
- >>> from __future__ import with_statement
- >>> with variables(1):
- ... print(isvar(1))
- True
- >>> print(isvar(1))
- False
- >>> # Normal approach
- >>> from unification import unify
- >>> x = var("x")
- >>> unify(x, 1)
- {~x: 1}
- >>> # Context Manager approach
- >>> with variables("x"):
- ... print(unify("x", 1))
- {'x': 1}
- """
- old_global_logic_variables = _global_logic_variables.copy()
- _global_logic_variables.update(set(variables))
- try:
- yield
- finally:
- _global_logic_variables.clear()
- _global_logic_variables.update(old_global_logic_variables)
|
