Lists: map, filter, sum

● Beginner4 min

map changes every item, filter keeps some, sum adds them up, and count, any, all and find ask questions.

fn main() {
    const prices = [120, 40, 300, 75]
    print(prices.map(p => p * 2))
    print(prices.filter(p => p > 100))
    print(prices.sum(p => p))
    print(prices.count(p => p > 100))
    print(prices.any(p => p > 250))
    print(prices.all(p => p > 0))
    print(prices.find(p => p < 50) ?? 0)
}

kavach run pipeline.kav

[240, 80, 600, 150][120, 300]5352truetrue40

Chained, they read like a sentence, and run as a single loop with no list built between the steps:

type Order {
    amount: Int
    paid: Bool
}

fn main() {
    const names = ["asha", "ravi", "meenakshi"]
    print(names.map(.upper()))
    print(names.filter(.len() > 4))
    const orders = [Order(amount: 300, paid: true), Order(amount: 120, paid: false)]
    print(orders.filter(.paid).sum(.amount))
}

kavach run dot.kav

["ASHA", "RAVI", "MEENAKSHI"]["meenakshi"]300

The first items, and the rest

take(n) gives the first n items, and skip(n) all but them. Asking for more than the list holds gives what there is:

fn main() {
    const queue = ["asha", "ravi", "meera", "john", "lin"]
    print(queue.take(2))
    print(queue.skip(2))
    print(queue.skip(2).take(2))
    print(queue.take(10).len())
}

kavach run take-skip.kav

["asha", "ravi"]["meera", "john", "lin"]["meera", "john"]5

What Kavach does for you

Chains become one loop
xs.map(f).filter(g).sum() runs as a single loop: no list is built between the steps.
fuse/hoist.rs