def assign_semantics(ccg_tree, semantic_index, tokens):
"""
Visit recursively the CCG tree in depth-first order, assigning lambda expressions
(semantics) to each node.
"""
category = ccg_tree.attrib['category']
if len(ccg_tree) == 0:
semantics = semantic_index.get_semantic_representation(ccg_tree, tokens)
ccg_tree.set('sem', str(semantics))
return
if len(ccg_tree) == 1:
assign_semantics(ccg_tree[0], semantic_index, tokens)
semantics = semantic_index.get_semantic_representation(ccg_tree, tokens)
ccg_tree.set('sem', str(semantics))
return
for child in ccg_tree:
assign_semantics(child, semantic_index, tokens)
combine_children_exprs(ccg_tree, tokens, semantic_index)
return
def combine_children_exprs(ccg_tree, tokens, semantic_index):
"""
Perform forward/backward function application/combination.
"""
assert len(ccg_tree) >= 2, \
'There should be at least two children to combine expressions: {0}'\
.format(ccg_tree)
# Assign coq types.
coq_types_left = ccg_tree[0].attrib.get('coq_type', "")
coq_types_right = ccg_tree[1].attrib.get('coq_type', "")
if coq_types_left and coq_types_right:
coq_types = coq_types_left + ' ||| ' + coq_types_right
elif coq_types_left:
coq_types = coq_types_left
else:
coq_types = coq_types_right
ccg_tree.set('coq_type', coq_types)
semantics = semantic_index.get_semantic_representation(ccg_tree, tokens)
if semantics:
ccg_tree.set('sem', str(semantics))
return None
# Back-off mechanism in case no semantic templates are available:
if is_forward_operation(ccg_tree):
function_index, argument_index = 0, 1
else:
function_index, argument_index = 1, 0
function = lexpr(ccg_tree[function_index].attrib['sem'])
argument = lexpr(ccg_tree[argument_index].attrib['sem'])
combination_operation = get_combination_op(ccg_tree)
if combination_operation == 'function_application':
evaluation = function(argument).simplify()
elif combination_operation == 'function_combination':
num_arguments = get_num_args(ccg_tree)
type_raised_function = type_raise(function, num_arguments)
evaluation = type_raised_function(argument).simplify()
else:
assert False, 'This node should be a function application or combination'\
.format(etree.tostring(ccg_tree, pretty_print=True))
ccg_tree.set('sem', str(evaluation))
return None
def combine_children_exprs(ccg_tree, tokens, semantic_index):
"""
Perform forward/backward function application/combination.
"""
assert len(ccg_tree) >= 2, \
'There should be at least two children to combine expressions: {0}'\
.format(ccg_tree)
# Assign coq types.
coq_types_left = ccg_tree[0].attrib.get('coq_type', "")
coq_types_right = ccg_tree[1].attrib.get('coq_type', "")
if coq_types_left and coq_types_right:
coq_types = coq_types_left + ' ||| ' + coq_types_right
elif coq_types_left:
coq_types = coq_types_left
else:
coq_types = coq_types_right
ccg_tree.set('coq_type', coq_types)
semantics = semantic_index.get_semantic_representation(ccg_tree, tokens)
if semantics:
ccg_tree.set('sem', str(semantics))
return None
# Back-off mechanism in case no semantic templates are available:
if is_forward_operation(ccg_tree):
function_index, argument_index = 0, 1
else:
function_index, argument_index = 1, 0
function = lexpr(ccg_tree[function_index].attrib['sem'])
argument = lexpr(ccg_tree[argument_index].attrib['sem'])
combination_operation = get_combination_op(ccg_tree)
if combination_operation == 'function_application':
evaluation = function(argument).simplify()
elif combination_operation == 'function_combination':
num_arguments = get_num_args(ccg_tree)
type_raised_function = type_raise(function, num_arguments)
evaluation = type_raised_function(argument).simplify()
else:
assert False, 'This node should be a function application or combination'\
.format(etree.tostring(ccg_tree, pretty_print=True))
ccg_tree.set('sem', str(evaluation))
return None
