So I have a code that read from another file, and then looks through it inside the lexer() function. That function works, but I have an error on the parse() function. It says indexerror, but I checked and could not find the problem. I am trying to get the function called getVARRIABLE() to return the error. I have checked the line at which the error happens, which is line 100. Any tips?
Error:
Traceback (most recent call last):
File "C:\Users\mcqui\OneDrive\Desktop\Programming language for capstones\main.py", line 134, in <module>
run()
File "C:\Users\mcqui\OneDrive\Desktop\Programming language for capstones\main.py", line 132, in run
parse(toks)
File "C:\Users\mcqui\OneDrive\Desktop\Programming language for capstones\main.py", line 102, in parse
if toks[i] " " toks[i 1][0:6] == "show STRING" or toks[i] " " toks[i 1][0:3] == "show NUM" or toks[i] " " toks[i 1][0:4] == "show EXPR" or toks[i] " " toks[i 1][0:3] == "show VAR":
IndexError: list index out of range
main.py:
from lib2to3.pgen2 import token
from sys import *
tokens = []
symbols = {}
def open_file(filename):
data = open(filename, 'r').read()
data = "<EOF>"
return data
def lexer(filecontents):
filecontents = list(filecontents)
tok = ""
state = 0
isexpr = 0
string = ""
var = ""
expr = ""
varstarted = 0
n = ""
for char in filecontents:
tok = char
if tok == " ":
if state == 0:
tok = ""
else:
tok = " "
elif tok =="\n" or tok =="<EOF>":
if expr != "" and isexpr == 1:
tokens.append("EXPR:" expr)
expr = ""
elif expr != "" and isexpr == 0:
tokens.append("NUM:" expr)
expr = ""
elif var != "":
tokens.append("VAR:" var)
var = ""
varstarted = 0
tok = ""
elif tok == '=' and state == 0:
if var != "":
tokens.append("VAR:" var)
var = ""
varstarted = 0
tokens.append("EQUALS")
tok = ""
elif tok == "var " and state == 0:
varstarted = 1
var = tok
tok = ""
elif varstarted == 1:
if tok == '<' or tok == '>':
if var != "":
tokens.append("VAR:" var)
var = ""
varstarted = 0
var = tok
tok = ""
elif tok == "show" or tok == 'SHOW':
tokens.append("show")
tok = ""
elif tok.isdigit():
expr = tok
tok = ""
elif tok == ' ' or tok=='-' or tok=='*'or tok=='/' or tok=='(' or tok==')':
isexpr = 1
expr =tok
tok = ""
elif tok == "\"":
if state == 0:
state = 1
elif state == 1:
tokens.append("STRING:" string "\"")
string = ""
state = 0
tok = ""
elif state == 1:
string = tok
tok = ""
return tokens
# print(tokens)
# return ''
def doAssign(varname, varvalue):
# To get back VAR variable just change to [4:]
symbols[varname[8:]] = varvalue
def getVARIABLE(varname):
varname = varname[8:]
if varname in symbols:
return symbols[varname]
else:
return "VARIABLE ERROR: Undefind VARIABLE"
def parse(toks):
i = 0
while(i < len(toks)):
if toks[i] " " toks[i 1][0:6] == "show STRING" or toks[i] " " toks[i 1][0:3] == "show NUM" or toks[i] " " toks[i 1][0:4] == "show EXPR" or toks[i] " " toks[i 1][0:3] == "show VAR":
if toks[i 1][0:6] == "STRING":
print(toks[i 1][8:-1])
elif toks[i 1][0:3] == "NUM":
print(toks[i 1][4:])
elif toks[i 1][0:4] == "EXPR":
print(eval(toks[i 1][5:]))
elif toks[i 1][0:3] == "VAR":
print(getVARIABLE(toks[i 1]))
i =2
elif toks[i][0:3] " " toks[i 1] " " toks[i 2][0:6]== "VAR EQUALS STRING" or toks[i][0:3] " " toks[i 1] " " toks[i 2][0:3]== "VAR EQUALS NUM" or toks[i][0:3] " " toks[i 1] " " toks[i 2][0:4]== "VAR EQUALS EXPR":
if toks[i 2][0:6] == "STRING":
doAssign(toks[i], toks[i 2])
elif toks[i 2][0:3] == "NUM":
doAssign(toks[i], toks[i 2])
elif toks[i 2][0:4] == "EXPR":
doAssign(toks[i],"NUM:" str(eval( toks[i 2][5:])))
i =3
print(symbols)
##################################################################################
def run():
data = open_file(argv[1])
toks = lexer(data)
parse(toks)
run()
input file:
var variable = 10 1308
show amog
CodePudding user response：
toks[i 1] is outside the list when you're on the last token, and toks[i 2] is outside when you're on the 2nd-to-last token. So check if you're in range before doing these tests.
You also need an else: case to increment i when none of the other cases match.
def parse(toks):
i = 0
while i < len(toks):
if i < len(toks) - 1 and (toks[i] " " toks[i 1][0:6] == "show STRING" or toks[i] " " toks[i 1][0:3] == "show NUM" or toks[i] " " toks[i 1][0:4] == "show EXPR" or toks[i] " " toks[i 1][0:3] == "show VAR"):
if toks[i 1][0:6] == "STRING":
print(toks[i 1][8:-1])
elif toks[i 1][0:3] == "NUM":
print(toks[i 1][4:])
elif toks[i 1][0:4] == "EXPR":
print(eval(toks[i 1][5:]))
elif toks[i 1][0:3] == "VAR":
print(getVARIABLE(toks[i 1]))
i =2
elif i < len(toks) - 2 and (toks[i][0:3] " " toks[i 1] " " toks[i 2][0:6]== "VAR EQUALS STRING" or toks[i][0:3] " " toks[i 1] " " toks[i 2][0:3]== "VAR EQUALS NUM" or toks[i][0:3] " " toks[i 1] " " toks[i 2][0:4]== "VAR EQUALS EXPR"):
if toks[i 2][0:6] == "STRING":
doAssign(toks[i], toks[i 2])
elif toks[i 2][0:3] == "NUM":
doAssign(toks[i], toks[i 2])
elif toks[i 2][0:4] == "EXPR":
doAssign(toks[i],"NUM:" str(eval( toks[i 2][5:])))
i =3
else:
i = 1
print(symbols)