def capture_token(self, token):
'''Captures an emitted token.
When a token is emitted if the last previously created part is a term
that *is* the same as the :attr:`IGeneratorToken.expression`, then this
last term should be removed from the particles collection.
This is because in a query like::
these((parent, child)
for parent in this
for child in parent.children)
The `parent.children` emits itself as a query part and immediately it
is transformed to a token.
:param token: The emitted token
:type token: :class:`IGeneratorToken`
'''
tokens = self._tokens
with context(UNPROXIFING_CONTEXT):
assert IGeneratorToken.providedBy(token)
parts = self._parts
if parts:
top = parts.pop(-1)
if token.expression is not top:
parts.append(top)
if token not in tokens:
tokens.append(token)
self._particles.append(token)
def __init__(self, **kwargs):
with context(UNPROXIFING_CONTEXT):
self._expression = expression = kwargs.get('expression')
assert IExpressionCapable.providedBy(expression)
self._token = None
self.token = token = kwargs.get('token')
assert IGeneratorToken.providedBy(token)
def __init__(self, **kwargs):
with context(UNPROXIFING_CONTEXT):
self._expression = expression = kwargs.get('expression')
assert IExpressionCapable.providedBy(expression)
self._token = None
self.token = token = kwargs.get('token')
assert IGeneratorToken.providedBy(token)
def capture_token(self, token):
'''Captures an emitted token.
When a token is emitted if the last previously created part is a term
that *is* the same as the :attr:`IGeneratorToken.expression`, then this
last term should be removed from the particles collection.
This is because in a query like::
these((parent, child)
for parent in this
for child in parent.children)
The `parent.children` emits itself as a query part and immediately it
is transformed to a token.
:param token: The emitted token
:type token: :class:`IGeneratorToken`
'''
tokens = self._tokens
with context(UNPROXIFING_CONTEXT):
assert IGeneratorToken.providedBy(token)
parts = self._parts
if parts:
top = parts.pop(-1)
if token.expression is not top:
parts.append(top)
if token not in tokens:
tokens.append(token)
self._particles.append(token)
def cmp_terms(t1, t2, strict=False):
'''Compares two terms in a partial order.
This is a *partial* compare operator. A term `t1 < t2` if and only if `t1`
is in the parent-chain of `t2`.
If `strict` is False the comparison between expressions will be made with
the `eq` operation; otherwise `is` will be used.
If either `t1` or `t2` are generator tokens it's
:attr:`~xotl.ql.interfaces.IGeneratorToken.expression` is used instead.
Examples::
>>> from xotl.ql.core import this, these
>>> t1 = this('a').b.c
>>> t2 = this('b').b.c.d
>>> t3 = this('a').b
>>> cmp_terms(t1, t3)
1
# But if equivalence is False neither t1 < t3 nor t3 < t1 holds.
>>> cmp_terms(t1, t3, True)
0
# Since t1 and t2 have no comon ancestor, they are not ordered.
>>> cmp_terms(t1, t2)
0
>>> query = these((child, brother)
... for parent in this
... for child in parent.children
... for brother in parent.children
... if child is not brother)
>>> t1, t2, t3 = query.tokens
>>> cmp_terms(t1, t2)
-1
>>> cmp_terms(t2, t3)
0
'''
import operator
if not strict:
test = operator.eq
else:
test = operator.is_
with context(UNPROXIFING_CONTEXT):
if IGeneratorToken.providedBy(t1):
t1 = t1.expression
if IGeneratorToken.providedBy(t2):
t2 = t2.expression
if test(t1, t2):
return 0
else:
t = t1
while t and not test(t, t2):
t = t.parent
if t:
return 1
t = t2
while t and not test(t, t1):
t = t.parent
if t:
return -1
else:
return 0