Implementation of 'unless statement' on Groovy & Clojure

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このコードが使われている記事

• GroovyとClojureでunlessを書いてみた

unless.clj

(use '[clojure.contrib.test-is :only (is)])

(defmacro unless
  ([test body]
    `(if (not ~test) ~body))
  ([test body else-body]
    `(if (not ~test) ~body ~else-body)))

(is (= 1 (unless false 1)))
(is (nil? (unless true 1)))
(is (= 1 (unless false 1 2)))
(is (= 2 (unless true 1 2)))

(is (= 25
      (apply +
        (filter #(unless (zero? (rem % 2)) true false) (range 10)))))

(is (= 3510
      (apply +
        (map #(unless (< % 5) (* 100 %) %) (range 10)))))

unless.groovy

class Unless {
  static def load() {
    Object.metaClass.unless = new Unless().&unless
  }
  Else unless(boolean test, Closure body) {
    if (! test) {
      body()
      return new Else(doStuff: false)
    } else {
      return new Else(doStuff: true)
    }
  }
  private class Else {
    boolean doStuff
    def 'else'(Closure body) {
      if (doStuff) body()
    }
  }
}

// loading unless method
Unless.load()

int sum1 = 0
10.times { i ->
  unless (i % 2 == 0) {
    sum1 += i
  }
}
assert sum1 == 25

int sum2 = 0
10.times { i ->
  unless (i < 5) {
    sum2 += 100 * i
  } 'else' {
    sum2 += i
  }
}
assert sum2 == 3510