def skip_whitespace(s, start):
	i = start
	while i < len(s) and s[i].isspace():
		i += 1

	return i


def str_row_col(s, i):
	k = 0
	(r, c) = (0, 0)
	for (r, line) in enumerate(s.splitlines(True)):
		c = i-k
		if k+len(line) > i:
			break
		else:
			k += len(line)
	return (r+1, c+1)


class ParserError(Exception):
	def __init__(self, msg, s, i):
		self.msg = msg
		(self.row, self.col) = str_row_col(s, i)
		self.context = s[i:i+16]

	def __str__(self):
		return "{0} at row {1}, col {2}, got '{3}...' instead".format(self.msg, self.row, self.col, self.context)


class ParserWarning(ParserError):
	pass