def evaluate_Predicate(context, query):
# We evaluate the left-hand side
left_value = context.evaluate(query.left)
# Then we go through the list of items in the resulting left-hand
# collection. For each item, we evaluate the predicate with the specified
# item as the context item. If the result of evaluating the predicate is
# a true collection (a collection with at least one true value), then we
# include the item in the list of values to return.
return [v for v in left_value if is_true_collection(context.new_with_item(v).evaluate(query.right))]
def flwor_FlworWhere(context, query, var_stream):
# This one's even easier. We get the expression to evaluat to check
# whether or not we want to allow each varset through
expr = query.expr
# Then we iterate over the varsets
for varset in var_stream:
# For each one, we evaluate the expression to see if we should let
# this varset on to further processing stages
expr_value = context.new_with_vars(varset).evaluate(expr)
# Then we check to see if the result was a true value
if is_true_collection(expr_value):
# It was, so we yield this varset.
yield varset
def evaluate_Satisfies(context, query):
name = query.name
expr_value = context.evaluate(query.expr)
some = query.type == "some"
for item in expr_value:
result = context.new_with_var(name, [item]).evaluate(query.condition)
truth = is_true_collection(result)
if some: # Checking for at least one to be true
if truth:
return [Boolean(True)]
else: # Checking for all to be true, so if one's false, we just quit
if not truth:
return [Boolean(False)]
if some: # Checking for some, but none of them were true
return [Boolean(False)]
else: # Checking for all, and none of them were false so we return true
return [Boolean(True)]
def evaluate_IfThenElse(context, query):
condition_value = context.evaluate(query.condition)
if is_true_collection(condition_value):
return context.evaluate(query.true)
else:
return context.evaluate(query.false)
def evaluate_Or(context, query):
left_value = context.evaluate(query.left)
if not is_true_collection(left_value):
return [Boolean(is_true_collection(context.evaluate(query.right)))]
else:
return [Boolean(True)]
