Extension functions on Iterable and Collection provide functional-style pipelines: map transforms each element, filter keeps those matching a predicate, flatten merges nested lists, groupBy builds a map of lists keyed by a selector, fold reduces to one value. Each step on List usually returns a new List — immutable pipelines.

map and filter
Full content is available with a subscription.
Get full access to all courses on the platform for one year with a single payment.
Unlike other platforms that charge per course, here you get everything for one price, and after one year of use there will be no automatic charge for the following year.