def multiplier():
if token.table == TABLE_ID:
return NodeAST(NodeAST.ID, token_line, token.index)
if token.table == TABLE_NUMBER:
return NodeAST(NodeAST.NUMBER, token_line, token.index)
if token.value == token.TRUE or token.value == token.FALSE:
return NodeAST(NodeAST.BOOL, token_line, token.index)
if token.value == token.NOT:
next_token()
m = multiplier()
if not m:
return None
return NodeAST(
NodeAST.EXPR, token_line,
NodeAST(NodeAST.OP, token_line, TABLE_KEYWORD, token.NOT), m, None)
if token.value == token.LPAR:
next_token()
e = expr()
if e and token.value == token.RPAR:
return e
return None
def read_stmt():
args = []
next_token()
if token.value == token.LPAR:
next_token()
if token.table != TABLE_ID:
print('Error [line ' + str(token_line) +
']: expected variable after \'(\'')
return None
args.append(NodeAST(NodeAST.ID, token_line, token.index))
next_token()
while token.value == token.COMMA:
next_token()
if token.table != TABLE_ID:
print('Error [line ' + str(token_line) +
']: expected variable after \'(\'')
return None
args.append(NodeAST(NodeAST.ID, token_line, token.index))
next_token()
if token.value == token.RPAR:
next_token()
return NodeAST(NodeAST.READ, token_line, *args)
print('Error [line ' + str(token_line) +
']: expected \'(\' after \'read\'')
return None
def if_stmt():
next_token()
cond = expr()
if cond:
if token.value == token.THEN:
next_token()
lhs = stmt()
if lhs:
if token.value == token.ELSE:
next_token()
rhs = stmt()
if rhs:
return NodeAST(NodeAST.IF, token_line, cond, lhs, rhs)
print('Error [line ' + str(token_line) +
']: expected statement after \'else\'')
return None
return NodeAST(NodeAST.IF, token_line, cond, lhs, None)
print('Error [line ' + str(token_line) +
']: expected statement after \'then\'')
return None
print('Error [line ' + str(token_line) +
']: expected \'then\' in \'if\' statement')
return None
print('Error [line ' + str(token_line) +
']: expected expression after \'if\'')
return None
def ass_stmt():
lhs = NodeAST(NodeAST.ID, token_line, token.index)
next_token()
if token.value == token.ASS:
next_token()
rhs = expr()
if rhs:
return NodeAST(NodeAST.ASS, token_line, lhs, rhs)
print('Error [line ' + str(token_line) +
']: expected expression after \'ass\'')
return None
print('Error [line ' + str(token_line) + ']: expected \'ass\'')
return None
def write_stmt():
next_token()
args = []
if token.value == token.LPAR:
next_token()
args.append(expr())
if not args[-1]:
print('Error [line ' + str(token_line) +
']: expected expression after \'(\'')
return None
while token.value == token.COMMA:
next_token()
args.append(expr())
if not args[-1]:
print('Error [line ' + str(token_line) +
']: expected expression')
return None
if token.table == TABLE_ID:
print('Error [line ' + str(token_line) + ']: expected \',\'')
return None
elif token.value == token.RPAR:
next_token()
return NodeAST(NodeAST.WRITE, token_line, *args)
else:
print('Error [line ' + str(token_line) + ']: expected \')')
return None
print('Error [line ' + str(token_line) + ']: expected \'(\'')
return None
def for_stmt():
next_token()
begin = ass_stmt()
if begin:
if token.value == token.TO:
next_token()
end = expr()
if end:
if token.value == token.DO:
next_token()
stmts = stmt()
if stmts:
return NodeAST(NodeAST.FOR, token_line, begin, end,
stmts)
print('Error [line ' + str(token_line) +
']: expected statement after \'do\'')
return None
print('Error [line ' + str(token_line) +
']: expected \'do\' in \'for\' statement')
return None
print('Error [line ' + str(token_line) +
']: expected expression after \'to\'')
return None
print('Error [line ' + str(token_line) +
']: expected \'to\' in \'for\' statement')
return None
print('Error [line ' + str(token_line) +
']: expected statement after \'for\'')
return None
def parse():
global errors
if token.value != token.PROGRAM:
print('Error [line ' + str(token_line) + ']: expected \'program\'')
return None
next_token()
if token.value != token.VAR:
print('Error [line ' + str(token_line) + ']: expected \'var\'')
return None
next_token()
decls = []
decls.append(declaration())
while decls[-1]:
if token.value == token.BEGIN:
break
decls.append(declaration())
if not decls:
print('Error [line ' + str(token_line) + ']: expected declarations')
return None
next_token()
stmts = []
result = stmt()
while True:
if not result:
if token.value == token.END or not token.value:
break
errors = True
while token.value != token.SEMICOLON:
next_token()
if not token.value:
break
next_token()
if token.value == token.END or not token.value:
break
result = stmt()
stmts.append(result)
if token.value != token.SEMICOLON:
print('Error [line ' + str(token_line) + ']: ' +
'expected \';\' after statement')
return None
next_token()
result = stmt()
if token.value != token.END:
print('Error [line ' + str(token_line) + ']: ' + 'expected \'end\'')
return None
next_token()
if token.value != token.DOT:
print('Error [line ' + str(token_line) + ']: ' +
'expected \'.\' after \'end\'')
return None
return NodeAST(NodeAST.PROGRAM, token_line, decls, stmts)
def operand():
lhs = summand()
if lhs:
op = sumop()
if op:
next_token()
rhs = operand()
if rhs:
return NodeAST(NodeAST.EXPR, token_line, op, lhs, rhs)
return None
return lhs
return None
def summand():
lhs = multiplier()
if lhs:
next_token()
op = mulop()
if op:
next_token()
rhs = summand()
if rhs:
return NodeAST(NodeAST.EXPR, token_line, op, lhs, rhs)
return None
return lhs
return None
def while_stmt():
next_token()
cond = expr()
if cond:
if token.value == token.DO:
next_token()
stmts = stmt()
if stmts:
return NodeAST(NodeAST.WHILE, token_line, cond, stmts)
print('Error [line ' + str(token_line) +
']: expected statement after \'do\'')
return None
print('Error [line ' + str(token_line) +
']: expected \'do\' in \'while\' statement')
return None
print('Error [line ' + str(token_line) +
']: expected expression after \'while\'')
return None
def stmt():
args = []
node = None
if token.table == TABLE_ID:
node = ass_stmt()
elif token.value == token.IF:
node = if_stmt()
elif token.value == token.WRITE:
node = write_stmt()
elif token.value == token.READ:
node = read_stmt()
elif token.value == token.FOR:
node = for_stmt()
elif token.value == token.WHILE:
node = while_stmt()
if node:
if token.value == token.COLON:
args.append(node)
while token.value == token.COLON:
next_token()
if token.table == TABLE_ID:
node = ass_stmt()
elif token.value == token.IF:
node = if_stmt()
elif token.value == token.WRITE:
node = write_stmt()
elif token.value == token.READ:
node = read_stmt()
elif token.value == token.FOR:
node = for_stmt()
elif token.value == token.WHILE:
node = while_stmt()
if not node:
return None
args.append(node)
return NodeAST(NodeAST.STMT_SEQ, token_line, *args)
return node
return None
def relop():
if (token.value == token.NOTEQUAL) or (token.value == token.EQUAL) or \
(token.value == token.LESS) or (token.value == token.GREAT) or \
(token.value == token.LESSEQUAL) or (token.value == token.GREATEQUAL):
return NodeAST(NodeAST.OP, token_line, TABLE_SEPARATOR, token.value)
return None
def sumop():
if token.value == token.PLUS or token.value == token.MINUS:
return NodeAST(NodeAST.OP, token_line, TABLE_SEPARATOR, token.value)
if token.value == token.OR:
return NodeAST(NodeAST.OP, token_line, TABLE_KEYWORD, token.value)
return None
def mulop():
if token.value == token.MUL or token.value == token.DIV:
return NodeAST(NodeAST.OP, token_line, TABLE_SEPARATOR, token.value)
if token.value == token.AND:
return NodeAST(NodeAST.OP, token_line, TABLE_KEYWORD, token.value)
return None