def parse_token_list_rec(self):
"""
Parses a tokenized arithmetic expression into a parse tree. It calls
itself recursively to handle bracketed subexpressions.
@return: Returns a token string.
@rtype: lems.parser.expr.ExprNode
@attention: Does not handle unary minuses at the moment. Needs to be
fixed.
"""
op_stack = Stack()
val_stack = Stack()
node_stack = Stack()
op_stack.push('$')
val_stack.push('$')
exit_loop = False
while self.token_list and not exit_loop:
token = self.token_list[0]
self.token_list = self.token_list[1:]
#print '###> ', token,op_stack,node_stack,val_stack
if token == '(':
node_stack.push(self.parse_token_list_rec())
val_stack.push('$')
elif self.is_func(token):
op_stack.push(token)
elif self.is_op(token):
if self.op_priority[op_stack.top()] >= \
self.op_priority[token]:
op = op_stack.pop()
if self.is_func(op):
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(Func1Node(op, right))
val_stack.push('$')
elif op == '~':
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(OpNode('-', ValueNode('0'), right))
val_stack.push('$')
else:
rval = val_stack.pop()
lval = val_stack.pop()
if lval == '$':
left = node_stack.pop()
else:
left = ValueNode(lval)
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(OpNode(op, left, right))
val_stack.push('$')
op_stack.push(token)
elif token == ')':
exit_loop = True
else:
val_stack.push(token)
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
while op_stack.top() != '$':
op = op_stack.pop()
if self.is_func(op):
right = Func1Node(op, right)
elif op == '~':
lval = val_stack.pop()
right = OpNode('-', ValueNode('0'), right)
else:
lval = val_stack.pop()
if lval == '$':
if node_stack.is_empty():
left = ValueNode('0')
else:
left = node_stack.pop()
else:
left = ValueNode(lval)
right = OpNode(op, left, right)
return right
def parse_token_list_rec(self):
"""
Parses a tokenized arithmetic expression into a parse tree. It calls
itself recursively to handle bracketed subexpressions.
@return: Returns a token string.
@rtype: lems.parser.expr.ExprNode
@attention: Does not handle unary minuses at the moment. Needs to be
fixed.
"""
op_stack = Stack()
val_stack = Stack()
node_stack = Stack()
op_stack.push('$')
val_stack.push('$')
exit_loop = False
while self.token_list and not exit_loop:
token = self.token_list[0]
self.token_list = self.token_list[1:]
#print '###> ', token,op_stack,node_stack,val_stack
if token == '(':
node_stack.push(self.parse_token_list_rec())
val_stack.push('$')
elif self.is_func(token):
op_stack.push(token)
elif self.is_op(token):
if self.op_priority[op_stack.top()] >= \
self.op_priority[token]:
op = op_stack.pop()
if self.is_func(op):
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(Func1Node(op, right))
val_stack.push('$')
elif op == '~':
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(OpNode('-', ValueNode('0'), right))
val_stack.push('$')
else:
rval = val_stack.pop()
lval = val_stack.pop()
if lval == '$':
left = node_stack.pop()
else:
left = ValueNode(lval)
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
node_stack.push(OpNode(op, left, right))
val_stack.push('$')
op_stack.push(token)
elif token == ')':
exit_loop = True
else:
val_stack.push(token)
rval = val_stack.pop()
if rval == '$':
right = node_stack.pop()
else:
right = ValueNode(rval)
while op_stack.top() != '$':
op = op_stack.pop()
if self.is_func(op):
right = Func1Node(op, right)
elif op == '~':
lval = val_stack.pop()
right = OpNode('-', ValueNode('0'), right)
else:
lval = val_stack.pop()
if lval == '$':
if node_stack.is_empty():
left = ValueNode('0')
else:
left = node_stack.pop()
else:
left = ValueNode(lval)
right = OpNode(op, left, right)
return right
