Programs, systems, and the ideas underneath.

func square(_ x: Int) -> Int {
    x * x
}

let squares = [1, 2, 3].map(square)
print(squares)   // [1, 4, 9]

Learn Swift

def square(x):
    return x * x

squares = list(map(square, [1, 2, 3]))
print(squares)   # [1, 4, 9]

CS61A

static int square(int x) {
    return x * x;
}

int[] squares = IntStream.of(1, 2, 3)
    .map(Main::square).toArray();   // [1, 4, 9]

CS61B

int square(int x) {
    return x * x;
}

int squares[] = {1, 2, 3};
for (int i = 0; i < 3; i++)
    squares[i] = square(squares[i]);   // {1, 4, 9}

CS61C