scanner.py

# id is {A..Z}
# const is {1..100}
# line_num is {1..1000}

#Bcode
#line   10
#id     11
#const  12
#if     13
#goto   14
#print  15
#stop   16
#op     17
#line_num    {#line, num}     num is {1..1000}
#id          {#id, ref}       ref is index 1..26 corresponded to A..Z
#const       {#const, value}  value is {1..100}
#IF          {#if, 0}
#GOTO        {#goto, num}     num is {1..1000}
#PRINT       {#print, 0}
#STOP        {#stop, 0}
#+           {#op, 1}
#-           {#op, 2}
#<           {#op, 3}
#=           {#op, 4}

class Scanner:

    def __init__(self,s):
        self.stream = []
        self.loc = s
        AZ = [chr(ord('A')+i) for i in range(26)]
        file = open(s,"r")
        for line in file:
            l = line.strip().split()
            i = 0
            while i < len(l):
                token = l[i]
                if token.upper() == "IF":
                    self.stream.append(("IF",0))
                elif token.upper() == "GOTO":
                    self.stream.append(("GOTO",0))
                elif token.upper() == "PRINT":
                    self.stream.append(("PRINT",0))
                elif token.upper() == "STOP":
                    self.stream.append(("STOP",0))
                elif token == "+":
                    self.stream.append(("+",1))
                elif token == "-":
                    self.stream.append(("-",2))
                elif token == "<":
                    self.stream.append(("<",3))
                elif token == "=":
                    self.stream.append(("=",4))
                elif token.upper() in AZ:
                    self.stream.append(("id",ord(token.upper()) - ord('A')))
                else:
                    self.stream.append(("number",int(token)))
                i += 1
        file.close()
        self.stream.append(("EOF",0))
    def getStream(self):
        return self.stream