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import keyword
from .compound_match import CompoundMatch
DISCARD = object()
class Pattern(tuple):
"""A matcher that binds a value to a name."""
__slots__ = ()
def __new__(cls, name: str):
if name == "_":
return DISCARD
if not name.isidentifier():
raise ValueError
if keyword.iskeyword(name):
return super().__new__(cls, (name,))
@property
def name(self):
"""Return the name of the matcher."""
return tuple.__getitem__(self, 0)
def __getitem__(self, other):
return AsPattern(self, other)
class AsPattern(CompoundMatch, tuple):
"""A matcher that contains further bindings."""
def __new__(cls, matcher: Pattern, match):
if match is DISCARD:
return matcher
return super().__new__(cls, (matcher, match))
def matcher(self):
"""Return the left-hand-side of the as-match."""
return self[0]
def match(self):
"""Return the right-hand-side of the as-match."""
return self[1]
def destructure(self, value):
if isinstance(value, AsPattern):
if value is self:
return (self.match, self.matcher)
return (value.match, value)
return (value, value)
mwchase /
python-structured-data
