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


def strRowCol(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=strRowCol(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