def __parse(self, tokens):
"""
The recursive parser that builds the parse tree from one line of
source code.
:param tokens: The tokens from the source line separated by whitespace
in a list of strings.
:exception: raises a syntax_error.SyntaxError with the message
'Incomplete statement' if the statement is incomplete (e.g.
there are no tokens left and this method was called).
:exception: raises a syntax_error.SyntaxError with the message
'Invalid token {token}' if an unrecognized token is
encountered (e.g. not one of the tokens listed above).
:return:
"""
#self, variable, expression, symTbl, token
if len(tokens) > 0:
token = tokens.pop(0)
else:
return #raise syntax_error.SyntaxError('Incomplete statement')
if token == self.COMMENT_TOKEN:
return None
elif token in self.PRINT_TOKEN:
if len(tokens) > 0:
return print_node.PrintNode(self.__parse(tokens))
else:
return print_node.PrintNode(None)
elif token in self.MATH_TOKENS:
leftChild = self.__parse(tokens)
rightChild = self.__parse(tokens)
if not isinstance(leftChild,
(literal_node.LiteralNode, math_node.MathNode,
variable_node.VariableNode)):
raise syntax_error.SyntaxError('Invalid Statement')
if not isinstance(rightChild,
(literal_node.LiteralNode, math_node.MathNode,
variable_node.VariableNode)):
raise syntax_error.SyntaxError('Invalid Statement')
return math_node.MathNode(leftChild, rightChild, token)
elif token == self.ASSIGNMENT_TOKEN:
return assignment_node.AssignmentNode(self.__parse(tokens),
self.__parse(tokens),
self.symTbl, token)
elif token.isdigit():
return literal_node.LiteralNode(token)
elif token.isidentifier():
return variable_node.VariableNode(token, self.symTbl)
else:
raise syntax_error.SyntaxError('Invalid token ' + token)
pass
def emit(self):
"""
Prints an infiex string representation of the source code that
is contained as root nodes in parseTree.
:return None
"""
for node in self.parseTrees:
str = print_node.PrintNode(node).emit()
print(str)
def __parse(self, tokens):
"""
The recursive parser that builds the parse tree from one line of
source code.
:param tokens: The tokens from the source line separated by whitespace
in a list of strings.
:exception: raises a syntax_error.SyntaxError with the message
'Incomplete statement' if the statement is incomplete (e.g.
there are no tokens left and this method was called).
:exception: raises a syntax_error.SyntaxError with the message
'Invalid token {token}' if an unrecognized token is
encountered (e.g. not one of the tokens listed above).
:return:
"""
if len(tokens) <= 0:
raise (syntax_error.SyntaxError("Invalid Expression"))
current = tokens[0]
if len(tokens) > 0:
if type(tokens) is str:
tokens = None
else:
tokens.pop(0)
if current == self.ASSIGNMENT_TOKEN:
if len(tokens) > 0:
return assignment_node.AssignmentNode(self.__parse(tokens.pop(0)),self.__parse(tokens),self.symTbl,'=')
else:
raise syntax_error.SyntaxError('Incomplete statement')
elif current in self.MATH_TOKENS:
return math_node.MathNode(self.__parse(tokens),self.__parse(tokens), current)
elif current == self.PRINT_TOKEN:
if len(tokens)>0:
return print_node.PrintNode(self.__parse(tokens))
else:
return print_node.PrintNode()
elif current.isdigit():
return literal_node.LiteralNode(current)
elif current.isalpha():
return variable_node.VariableNode(current,self.symTbl)
elif current == self.COMMENT_TOKEN:
pass
elif current is None:
raise syntax_error.SyntaxError('Incomplete statement')
else:
raise syntax_error.SyntaxError('Invalid token ' + current)
def __parse(self, tokens):
"""
The recursive parser that builds the parse tree from one line of
source code.
:param tokens: The tokens from the source line separated by whitespace
in a list of strings.
:exception: raises a syntax_error.SyntaxError with the message
'Incomplete statement' if the statement is incomplete (e.g.
there are no tokens left and this method was called).
:exception: raises a syntax_error.SyntaxError with the message
'Invalid token {token}' if an unrecognized token is
encountered (e.g. not one of the tokens listed above).
:return: the object of one of node classes based on the type token.
Node classes: literal_node.LiteralNode, variable_node.VariableNode,
assignment_node.AssignmentNode, print_node.PrintNode,
math_node.MathNode
"""
if len(tokens) is 0:
raise syntax_error.SyntaxError('Incomplete statement')
token = tokens.pop()
if token.isdigit():
return literal_node.LiteralNode(token)
elif token.isidentifier():
return variable_node.VariableNode(token, self.symTbl)
elif token is self.ASSIGNMENT_TOKEN:
return assignment_node.AssignmentNode(self.__parse(tokens),
self.__parse(tokens), self.symTbl, token)
elif token is self.PRINT_TOKEN:
if len(tokens) > 0:
return print_node.PrintNode(self.__parse(tokens))
else:
return print_node.PrintNode()
elif token in self.MATH_TOKENS:
return math_node.MathNode(self.__parse(tokens), self.__parse(tokens), token)
else:
raise syntax_error.SyntaxError('Invalid token ' + token)
def __parse(self, tokens):
"""
The recursive parser that builds the parse tree from one line of
source code.
:param tokens: The tokens from the source line separated by whitespace
in a list of strings.
:exception: raises a syntax_error.SyntaxError with the message
'Incomplete statement' if the statement is incomplete (e.g.
there are no tokens left and this method was called).
:exception: raises a syntax_error.SyntaxError with the message
'Invalid token {token}' if an unrecognized token is
encountered (e.g. not one of the tokens listed above).
:return:
"""
if len(tokens) == 0:
return
elif tokens[0].isidentifier():
node = variable_node.VariableNode(tokens[0], self.symTbl)
self.parseTrees.append(node)
elif tokens[0].isdigit():
node = literal_node.LiteralNode(int(tokens[0]))
self.parseTrees.append(node)
elif tokens[0] == '=':
node = assignment_node.AssignmentNode(self.parseTrees.pop(),
self.parseTrees.pop(),
self.symTbl, tokens[0])
self.parseTrees.append(node)
elif tokens[0] == '@':
node = print_node.PrintNode(self.parseTrees.pop())
self.parseTrees.append(node)
elif tokens[0] in self.MATH_TOKENS:
x = self.parseTrees.pop()
y = self.parseTrees.pop()
if not isinstance(x,
(variable_node.VariableNode,
literal_node.LiteralNode, math_node.MathNode)):
raise syntax_error.SyntaxError('Incomplete Statement')
if not isinstance(y,
(variable_node.VariableNode,
literal_node.LiteralNode, math_node.MathNode)):
raise syntax_error.SyntaxError('Incomplete Statement')
node = math_node.MathNode(x, y, tokens[0])
self.parseTrees.append(node)
else:
raise syntax_error.SyntaxError("Invalid token")
self.__parse(tokens[1:])
"""
def parse(self):
"""
The public parse is responsible for looping over the lines of
source code and constructing the parseTree, as a series of
calls to the helper function that are appended to this list.
It needs to handle and display any syntax_error.SyntaxError
exceptions that get raised.
: return None
"""
count = 1
fh = open(self.srcFile)
for i in fh:
try:
self.lineNum = count
tokens = i.split()
if i[0] == '#' or tokens == []:
count += 1
continue
elif any(self.MATH_TOKENS) in tokens:
if len(tokens) < 3:
raise syntax_error.SyntaxError("Incomplete Statement")
if '=' in tokens[1:]:
count += 1
raise syntax_error.SyntaxError("Invalid Token")
if i[0] == '=' or i[0] == '@':
count += 1
if len(tokens) == 1:
if tokens[0] == '@':
node = print_node.PrintNode(
literal_node.LiteralNode(' '))
self.parseTrees.append(node)
else:
if '@' in tokens[1:]:
raise syntax_error.SyntaxError(
"Bad assignment expression")
raise syntax_error.SyntaxError(
"Incomplete Statement")
self.__parse(tokens[::-1])
else:
count += 1
if not (i[0] in self.MATH_TOKENS):
raise syntax_error.SyntaxError("Invalid Token")
except syntax_error.SyntaxError as syn:
self.syntaxError = True
print("Line ", self.lineNum, " ", syn)
def parse(self):
"""
The public parse is responsible for looping over the lines of
source code and constructing the parseTree, as a series of
calls to the helper function that are appended to this list.
It needs to handle and display any syntax_error.SyntaxError
exceptions that get raised.
: return None
"""
file = open(self.srcFile)
for line in file:
self.lineNum += 1
tokens = line.split()
# empty line
if len(tokens) == 0:
continue
# assignment statement
if tokens[0] == self.ASSIGNMENT_TOKEN:
# lack of tokens
if len(tokens) < 3:
self.syntaxError = True
# error message: Incomplete statement
print("\nFile \"%s\", line %d" %
(self.srcFile, self.lineNum),
file=sys.stderr)
print(" %sSyntaxError: Incomplete statement" % line,
file=sys.stderr)
continue
# left token is not valid variable name
if not tokens[1].isidentifier():
self.syntaxError = True
# error message: Bad assignment to non-variable
print("\nFile \"%s\", line %d" %
(self.srcFile, self.lineNum),
file=sys.stderr)
print(" %sSyntaxError: Bad assignment to non-variable" %
line,
file=sys.stderr)
continue
# construct parse tree for expression on the right
expression = self.__parse(tokens[2:])
# error raised during the construction of parse tree
if isinstance(expression, syntax_error.SyntaxError):
# print out the error message
print("\nFile \"%s\", line %d" %
(self.srcFile, self.lineNum),
file=sys.stderr)
print(" %sSyntaxError: %s" % (line, expression),
file=sys.stderr)
else:
# create a new AssignmentNode
self.parseTrees.append(
assignment_node.AssignmentNode(
variable_node.VariableNode(tokens[1], self.symTbl),
expression, self.symTbl, tokens[0]))
# print statement
elif tokens[0] == self.PRINT_TOKEN:
# empty expression
if len(tokens) == 1:
self.parseTrees.append(print_node.PrintNode(None))
else:
# construct parse tree for the expression
expression = self.__parse(tokens[1:])
# create a new PrintNode
self.parseTrees.append(print_node.PrintNode(expression))
# comment line
elif tokens[0] == self.COMMENT_TOKEN:
continue
else:
self.syntaxError = True
# error message: Invalid token
print("\nFile \"%s\", line %d" % (self.srcFile, self.lineNum),
file=sys.stderr)
print(" %sSyntaxError: Invalid token %s" % (line, tokens[0]),
file=sys.stderr)
file.close()