def parse_base_list(self):
"""BaseList = (BASE)*"""
tree = Tree('BaseList')
while not self._scanner.is_end() and not self._scanner.is_next('}'):
tree.append(self.parse_base())
return tree
def parse_exp(self):
"""EXP = ITEM ([+-*/] ITEM)? """
tree = Tree('EXP') \
.append(self.parse_item())
if self._scanner.is_next('OP'):
tree.append(self._scanner.get_next('OP')) \
.append(self.parse_item())
return tree
def parse_stmt(self):
"""STMT = 'return' id | id '=' EXP | id ('++'|'--') """
tree = Tree('STMT')
if self._scanner.is_next('return'):
tree.append(self._scanner.get_next('return')) \
.append(self.parse_id())
else:
tree.append(self.parse_id())
if self._scanner.is_next('ASSIGN'):
tree.append(self._scanner.get_next('ASSIGN')) \
.append(self.parse_exp())
else:
tree.append(self._scanner.get_next('UnaryOP'))
return tree
def parse_cond(self):
"""COND = EXP ('=='|'!='|'<='|'>='|'<'|'>') EXP"""
tree = Tree('COND') \
.append(self.parse_exp()) \
.append(self._scanner.get_next('COND')) \
.append(self.parse_exp())
return tree
def parse_block(self):
"""BLOCK = '{' BaseList '}' """
tree = Tree('BLOCK') \
.append(self._scanner.get_next('{')) \
.append(self.parse_base_list()) \
.append(self._scanner.get_next('}'))
return tree
def parse_base(self):
"""BASE = FOR | STMT ';' """
tree = Tree('BASE')
if self._scanner.is_next('for'):
tree.append(self.parse_for())
else:
tree.append(self.parse_stmt())
tree.append(self._scanner.get_next(';'))
return tree
def parse_for(self):
"""FOR = 'for' '(' STMT ';' COND ';' STMT ')' BLOCK """
tree = Tree('FOR') \
.append(self._scanner.get_next('for')) \
.append(self._scanner.get_next('(')) \
.append(self.parse_stmt()) \
.append(self._scanner.get_next('END')) \
.append(self.parse_cond()) \
.append(self._scanner.get_next('END')) \
.append(self.parse_stmt()) \
.append(self._scanner.get_next(')')) \
.append(self.parse_block())
return tree
def parse_item(self):
"""ITEM = id | number """
tree = Tree('ITEM')
if self._scanner.is_next('ID'):
tree.append(self.parse_id())
else:
tree.append(self.parse_number())
return tree
def parse_prog(self):
"""PROG = BaseList """
return Tree('PROG').append(self.parse_base_list())
def parse_number(self):
"""number = [0-9]+"""
tree = Tree('Number') \
.append(self._scanner.get_next('NUMBER'))
return tree
def parse_id(self):
"""id = [A-Za-z_][A-Za-z0-9_]*"""
tree = Tree('ID') \
.append(self._scanner.get_next('ID'))
return tree