tvl-depot/users/wpcarro/scratch/simple-select/scanner.py

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# According to Crafting Interpreters, the only two primitives that a
# scanner/lexer needs are peek and advance; other functions (e.g. match) are
# nice-to-haves.
class Scanner(object):
def __init__(self, chars):
self.i = 0
self.chars = chars
def exhausted(self):
return self.i >= len(self.chars)
def peek(self, n=0):
return self.chars[self.i + n] if self.i in range(0, len(self.chars)) else '\0'
def advance(self):
result = self.peek()
self.i += 1
return result
def match(self, x):
if self.exhausted():
return False
if self.peek() == x:
self.advance()
return True
else:
return False