Functions as values ​

map, filter and reduce work on arrays and ranges, and the pipeline operator |> passes a value into the next call as its first argument, so data reads left to right:

let total = [5, 12, 8, 20]
    |> filter(fn(n) => n > 6)
    |> map(fn(n) => n * 2)
    |> reduce(fn(sum, n) => sum + n, 0);

print(total);   // 80

_ leaves a gap to fill later: let double = multiply(_, 2); makes a function that takes the missing argument.

Your turn ​

Use a pipeline to print the squares of the odd numbers from 1 to 9.