matches.clj

(ns user)

(def matches?
  (let [match-map {\{ \}
                   \[ \]
                   \( \)}
        open-set (set (keys match-map))
        close-set (set (vals match-map))]
    (fn [input]
      (try
        (empty?
          (reduce
            (fn [acc c]
              (cond
                (open-set c) (conj acc c)
                (close-set c) (let [[x & rest] acc]
                                (if (= (match-map x) c)
                                  rest
                                  (throw (Exception.))))
                :else acc))
            (list)
            input))
        (catch Exception e false)))))

(assert (matches? "{foo}"))
(assert (not (matches? "foo}")))
(assert (not (matches? "{foo")))

matches.scala

import scala.util.Try

object Matches {

  val MatchMap = Map('{' -> '}', '[' -> ']', '(' -> ')')

  def doesMatch(input: String): Boolean =
    Try(input.foldLeft(List[Char]()) { (acc, c) =>
        if (MatchMap.keySet.contains(c))
          c :: acc
        else if (MatchMap.values.toSet.contains(c))
          acc match {
            case x :: rest if MatchMap(x) == c => rest
          }
        else
          acc
      }.isEmpty).getOrElse(false)

  assert(doesMatch("{{foo} [bar] (baz)}"))
  assert(!doesMatch("{foo(})"))

}