コレクションをぶんまわしてみる

gistfile1.groovy

// Original source written by irof.

List list = [
    [color:'blue', weight:10],
    [color:'red', weight:30],
    [color:'blue', weight:50],
]

// Javaで
int weight1 = 0;
for (def e : list) {
    if (e.color == 'blue')
        weight1 += e.weight;
}
assert weight1 == 60

// groovyで
int weight2 = list
    .findAll { it.color == 'blue' }
    .inject(0) { acc, e -> acc + e.weight }
assert weight2 == 60


// Lambdaだとこうなるっぽい？
int weight3 = list
    .filter { it -> it.color == 'blue' }
    .reduce (0, { acc, e -> acc + e.weight });
assert weight3 == 60

other-pattern.clj

// こんな感じか？

// Scalaで
int weight4 = list.filter(_.color == "blue").reduce(_.weight + _.weight)

// Clojureで
// 多分間違ってるけどこんなイメージだよな
(def weight5 (->> list
                  (filter (= (% color "blue"))
                  (reduce + (first %) (rest %))))