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Parser.py
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Parser.py
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from BooleanExpression import BooleanExpression
from BinaryExpression import BinaryExpression
from LexicalAnalyzer import LexicalAnalyzer
from ParserException import ParserException
from Assignment import Assignment
from Constant import Constant
from Id import Id
class Parser:
def __init__(self, fileName):
self.lex = LexicalAnalyzer(fileName)
def parse(self):
tok = self.lex.getNextToken()
if tok.getTokType() == "FUNCTION_TOK":
tok = self.lex.getNextToken().getTokType()
if tok == "ID_TOK":
tok = self.lex.getNextToken().getTokType()
if tok == "OPENP_TOK":
tok = self.lex.getNextToken().getTokType()
if tok == "CLOSEP_TOK":
self.getBlock()
tok = self.lex.getNextToken().getTokType()
if tok != "END_TOK":
raise ParserException("END expected")
else:
raise ParserException(") expected")
else:
raise ParserException("( expected")
else:
raise ParserException("ID expected")
else:
raise ParserException("FUNCTION expected")
def getBlock(self):
tok = self.lex.getLookaheadToken()
if(tok.getTokType() != "EOS_TOK") and (tok.getTokType() != "END_TOK") and (tok.getTokType() != "UNTIL_TOK"):
self.getStatement()
self.getBlock()
def getStatement(self):
tok = self.lex.getLookaheadToken()
if tok.getTokType() == "IF_TOK":
self.resolveIf()
elif tok.getTokType() == "WHILE_TOK":
self.resolveWhile()
elif tok.getTokType() == "REPEAT_TOK":
self.resolveRepeat()
elif tok.getTokType() == "PRINT_TOK":
self.printState()
elif tok.getTokType() == "ID_TOK":
self.Assign()
elif tok.getTokType() == "ELSE_TOK":
return
elif tok.getTokType() == "UNTIL_TOK":
return
else:
raise ParserException("Statement expected")
def resolveIf(self):
tok = self.lex.getLookaheadToken()
if self.getBooleanExpression().evaluate() == True:
tok = self.lex.getNextToken()
if tok.getTokType() == "THEN_TOK":
self.getBlock()
tok = self.lex.getNextToken()
if tok.getTokType() == "ELSE_TOK":
while tok.getTokType() != "END_TOK":
tok = self.lex.getNextToken()
if tok.getTokType() == "END_TOK":
return
else:
raise ParserException("ELSE expected")
else:
raise ParserException("THEN expected")
else:
while tok.getTokType() != "ELSE_TOK":
tok = self.lex.getNextToken()
self.getBlock()
tok = self.lex.getNextToken()
if tok.getTokType() == "END_TOK":
return
else:
raise ParserException("END expected")
def resolveWhile(self):
whileCondition = self.getBooleanExpression()
tok = self.lex.getNextToken()
if tok.getTokType() == "DO_TOK":
while whileCondition.evaluate() == True:
save1 = self.lex.tokenList[:]
self.getBlock()
save2 = self.lex.tokenList[:]
self.lex.tokenList = save1[:]
self.lex.tokenList = save2[:]
tok = self.lex.getNextToken().getTokType()
if tok == "END_TOK":
return
else:
raise ParserException("END expected")
else:
raise ParserException("DO expected")
def resolveRepeat(self):
save1 = self.lex.tokenList[:]
self.lex.getNextToken()
self.getBlock()
repeatCondition = self.getBooleanExpression()
if repeatCondition.evaluate() != True:
self.lex.tokenList = save1[:]
self.resolveRepeat()
def printState(self):
tok = self.lex.getNextToken()
if tok.getTokType() != "PRINT_TOK":
raise ParserException("PRINT expected")
tok = self.lex.getNextToken()
if tok.getTokType() == "OPENP_TOK":
print (self.getExpression().evaluate())
tok = self.lex.getNextToken()
if tok.getTokType() != "CLOSEP_TOK":
raise ParserException(") expected ")
else:
raise ParserException("( expected ")
def Assign(self):
var = self.getId()
tok = self.lex.getNextToken()
self.match(tok, "ASSIGN_TOK")
expr = self.getExpression()
Assignment(var, expr).execute()
def getExpression(self):
tok = self.lex.getLookaheadToken()
if tok.getTokType() == "ADD_TOK" or tok.getTokType() == "MUL_TOK" or tok.getTokType() == "SUB_TOK" or tok.getTokType() == "DIV_TOK":
expr = self.getBinaryExpression()
elif tok.getTokType() == "ID_TOK":
expr = self.getId()
else:
expr = self.getConstant()
return expr
def getBinaryExpression(self):
tok = self.lex.getNextToken()
if tok.getTokType() == "ADD_TOK":
self.match(tok, "ADD_TOK")
op = "ADD_OP"
elif tok.getTokType() == "MUL_TOK":
self.match(tok, "MUL_TOK")
op = "MUL_OP"
elif tok.getTokType() == "SUB_TOK":
self.match(tok, "SUB_TOK")
op = "SUB_OP"
elif tok.getTokType() == "DIV_TOK":
self.match(tok, "DIV_TOK")
op = "DIV_OP"
else:
raise ParserException ("Operator expected.")
expr1 = self.getExpression()
expr2 = self.getExpression()
return BinaryExpression(op, expr1, expr2)
def getBooleanExpression(self):
self.lex.getNextToken()
tok = self.lex.getNextToken()
if tok.getTokType() == "LE_TOK":
self.match(tok, "LE_TOK")
op = "LE_OP"
elif tok.getTokType() == "LT_TOK":
self.match(tok, "LT_TOK")
op = "LT_OP"
elif tok.getTokType() == "GE_TOK":
self.match(tok, "GE_TOK")
op = "GE_OP"
elif tok.getTokType() == "GT_TOK":
self.match(tok, "GT_TOK")
op = "GT_OP"
elif tok.getTokType() == "EQ_TOK":
self.match(tok, "EQ_TOK")
op = "EQ_OP"
elif tok.getTokType() == "NE_TOK":
self.match(tok, "NE_TOK")
op = "NE_OP"
else:
raise ParserException ("Operator expected.")
expr1 = self.getExpression()
expr2 = self.getExpression()
return BooleanExpression(op, expr1, expr2)
def getId(self):
tok = self.lex.getNextToken()
self.match(tok, "ID_TOK")
return Id(tok.getLexeme())
def getConstant(self):
tok = self.lex.getNextToken()
self.match(tok, "CONST_TOK")
value = int(tok.getLexeme())
return Constant(value)
def match(self, tok, tokType):
if tok.getTokType() != tokType:
raise ParserException ("Token of type " + tokType + "expected.")