Class Environment

18-with-match/lispy/py3.9/lis.py:62–71

A ChainMap that allows changing an item in-place.

################ Global Environment

class Environment(ChainMap[Symbol, Any]):
    "A ChainMap that allows changing an item in-place."

    def change(self, key: Symbol, value: Any) -> None:
        "Find where key is defined and change the value there."
        for map in self.maps:
            if key in map:
                map[key] = value  # type: ignore[index]
                return
        raise KeyError(key)


def standard_env() -> Environment: