object Solution {
    def myAtoi(s: String): Int = {
        // well, ignores invalid text, instead of returing 0.
        s.foldRight((0, 1))((v, acc) =>
                           v match {
                               case '-' => (acc._1* -1,acc._2)
                               case v if '0' to '9' contains v => (acc._1+(v-'0')*acc._2, acc._2*10)
                               case _ => acc
                           })._1
    }
}