Aug-26-2021, 06:40 PM
It turns out that treating the data in your programs as immutable values can be hugely beneficial in terms of how to think about programs - Rich Hickey has an excellent talk on this, titled The Value of Values. It's a shame that we still teach people how to program quite imperatively; most languages these days have a lot of useful abstractions that let you program more declaratively. The problem here can be expressed as: pair up each item with its index (
enumerate), keep the pairs with the indices that you want (filter) and then from each pair, select only the items (map). The list comprehension shown above neatly expresses that. Kevlin Henney has a great talk on programming declaratively, titled Declarative Thinking, Declarative Practice and the Toolz library provides a set of functions to help programming that way, beyond what's in the standard library.