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Scanner.py
66 lines (59 loc) · 1.92 KB
/
Scanner.py
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from Tokens import tokenize
import Tokens
from Errors import ParseError
class Scanner:
def __init__(self, codeString):
self.tokenList = [ token for token in tokenize(codeString) ]
# Insert explicit EOF token
self.tokenList.append(Tokens.EOF())
self.index = 0
self.fastForward()
def fastForward(self):
"""Skips past whitespace and comments."""
done = False
while not done:
token = self.tokenList[self.index]
if token.name != "Space" and token.name != "SingleComment" \
and token.name != "MultiComment":
done = True
else:
self.index += 1
def lookAhead(self):
return self.tokenList[self.index]
def match(self, type = None, value = None):
token = self.tokenList[self.index]
if token.compatible(type, value):
# Advance to the next meaningful token
self.index += 1
self.fastForward()
# Return the stored token
return token
else:
errMessage = "Token %s did not match against" % token
if type is not None:
errMessage += " type %s" % type
if value is not None:
errMessage += " value %s" % value
raise ParseError(errMessage, token)
def testScanner(filename = None):
if filename != None:
# Read code from file
f = open(filename, 'r')
code = f.read()
f.close()
else:
# Use pre-canned code
code = """
set x to 14 + 3 # Single-line comment
print (x - 4) * 2 #
#-- Multiline comment
containing #- various stuff #--#
#-## Another multiline -#
"""
scanner = Scanner(code)
for token in scanner.tokenList:
if token.name != "Space":
print(token)
if __name__ == "__main__":
#testScanner("test1.zeph")
testScanner()