def eval_(text: Value) -> Value:
""" Evaluates `text` as Knight code, returning its result. """
value = Value.parse(Stream(str(text)))
if value is None:
raise ParseError('Nothing to parse.')
else:
return value.run()
def parse(cls, stream: Stream) -> Union[None, String]:
"""
Parses a `String` from the `stream`, returning `None` if the
nothing can be parsed.
If a starting quote is matched and no ending quote is, then a
`ParseError` will be raised.
"""
quote = stream.matches(String.BEGIN_REGEX)
if not quote:
return None
regex = String.SINGLE_REGEX if quote == "'" else String.DOUBLE_REGEX
body = stream.matches(regex, 1)
if body is None:
raise ParseError(f'unterminated string encountered: {stream}')
else:
return String(body)
def parse(cls, stream: Stream) -> Union[None, Boolean]:
""" Parses a `Boolean` if the stream starts with `T` or `F`. """
if match := stream.matches(Boolean.REGEX, 1):
return cls(match == 'T')
def parse(cls, stream: Stream) -> Union[None, Boolean]:
""" Attempts to parse a `Boolean """
if match := stream.matches(r'([TF])[A-Z]*', 1):
return cls(match == 'T')
def parse(cls, stream: Stream) -> Union[None, Null]:
""" Parses `Null` if the stream starts with `N`. """
if match := stream.matches(r'N[A-Z]*'):
return cls()
def parse(cls, stream: Stream) -> Union[None, Null]:
""" Parses `Null` if the stream starts with `N`. """
if stream.matches(Null.REGEX):
return cls()
else:
return None