【Groovy】List对象的transpose和inject方法的使用

transpose()方法实际上就是数学中矩阵的转置，简单的来说就是行和列的交换：?

assert [[1,4],[2,5],[3,6]] == [list1,list2].transpose() 

transpose()不止可以用于两个List，还能用于多个List。譬如，我们有第三个List：?

def list3 = [7,8,9]

我们可以这样检查是否满足“list3 > list2 > list1”（每个对应的元素）：?

assert [list1,list2,list3].transpose().every { a,b,c ->
    a < b && b < c
}
assert [[1,4,7],5,8],6,9]] == [list1,list3].transpose()

有一点需要注意的是，如果List的长度不一，则取最短的长度：?

def list4 = [1,1,1]
def list5 = [2,2]
assert [[1,2],[1,2]] == [list4,list5].transpose()

def list = [1,2,3]
result = list.inject(0){s,l -> s += l }
assert 6 == result

def list = ['like','groovy']
result = list.inject('I'){s,l -> "$s $l" }
assert "I like groovy" == result

def a = [1,3]
def b = [4,6]
def m = [a,b].transpose().inject([:]) { s,l -> s + [(l[0]): l[1]] }
assert m == [1: 4,2: 5,3: 6]