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"""
Python Lexical Analyser
Actions for use in token specifications
"""
class Action:
def perform(self, token_stream, text):
pass # abstract
def __copy__(self):
return self # immutable, no need to copy
def __deepcopy__(self, memo):
return self # immutable, no need to copy
class Return(Action):
"""
Internal Plex action which causes |value| to
be returned as the value of the associated token
"""
def __init__(self, value):
self.value = value
def perform(self, token_stream, text):
return self.value
def __repr__(self):
return "Return(%r)" % self.value
class Call(Action):
"""
Internal Plex action which causes a function to be called.
"""
def __init__(self, function):
self.function = function
def perform(self, token_stream, text):
return self.function(token_stream, text)
def __repr__(self):
return "Call(%s)" % self.function.__name__
class Method(Action):
"""
Plex action that calls a specific method on the token stream,
passing the matched text and any provided constant keyword arguments.
"""
def __init__(self, name, **kwargs):
self.name = name
self.kwargs = kwargs or None
def perform(self, token_stream, text):
method = getattr(token_stream, self.name)
# self.kwargs is almost always unused => avoid call overhead
return method(text, **self.kwargs) if self.kwargs is not None else method(text)
def __repr__(self):
kwargs = (
', '.join(sorted(['%s=%r' % item for item in self.kwargs.items()]))
if self.kwargs is not None else '')
return "Method(%s%s%s)" % (self.name, ', ' if kwargs else '', kwargs)
class Begin(Action):
"""
Begin(state_name) is a Plex action which causes the Scanner to
enter the state |state_name|. See the docstring of Plex.Lexicon
for more information.
"""
def __init__(self, state_name):
self.state_name = state_name
def perform(self, token_stream, text):
token_stream.begin(self.state_name)
def __repr__(self):
return "Begin(%s)" % self.state_name
class Ignore(Action):
"""
IGNORE is a Plex action which causes its associated token
to be ignored. See the docstring of Plex.Lexicon for more
information.
"""
def perform(self, token_stream, text):
return None
def __repr__(self):
return "IGNORE"
IGNORE = Ignore()
class Text(Action):
"""
TEXT is a Plex action which causes the text of a token to
be returned as the value of the token. See the docstring of
Plex.Lexicon for more information.
"""
def perform(self, token_stream, text):
return text
def __repr__(self):
return "TEXT"
TEXT = Text()
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