import gll

ws  = gll.skipmany(gll.whitespace(), tag="spaces")
num = gll.many1(gll.digit(), tag="number")
op  = gll.string("+", tag="op") | gll.string("-", tag="op")

expr = gll.seq(num, ws, op, ws, num, tag="expr")

parser = gll.many(expr)