InfoQ
10 HN recommenders · recommended in 13 months, 2014–2023
31:44 · 145K views · Oct 8, 2012
Rich Hickey's JaxConf 2012 keynote examines what values are and why immutable values matter as information systems grow more complex and data gets bigger. It contrasts places with values and builds the case for immutability.
HN commenters cite it as the talk that convinced them of immutability and functional programming.
13 comments from Hacker News
Immutability has been pretty hot of late, though still controversial. There are several popular languages which encourage or even force immutability (Elixir, Clojure). What sold me on the idea was Rich Hickey's talk, "The Value of Values": this video I look at it as mostly a safety net: I'd rather use const by default, unless I have a good reason to be able to mutate the variable. (To flip it around: what problem does being mutable-by-default solve?) 9 times out of 10, I don't need to change the value for the lifecycle of the function; and often if I do, the code is cleaner anyway if I use an immutable pattern (such as `const foo = bar.map()` rather than `for(x in bar) foo.push()`). Thanks to the magic of Merkle trees, we can generally make fresh pointers without it costing much memory overhead.
Most software isn’t FAANG. In the long tail of database size, I’d guess 95%+ of databases are smaller than a few hundred megs. And at that size, storage is cheap and storing a full historical record of changes should absolutely be the default. Rich Hickey has a great talk on this a few years ago talking about the difference between Place and Value. He says accountants learned this lesson hundreds of years ago with bookkeeping. Users just don’t generate much data relative to the size of our disks. Well worth a watch, especially if you disagree: this video
Rich Hickey's "Value of Values"[0] is what finally sold me on the benefits of pure functional programming and immutable data structures. (It remains horrifying to continue working with MySQL in my day job, knowing that every UPDATE is potentially a destructive action with no history and no undo.) [0]: this video
Simple Made Easy ( [LINK] ) The Language of the System ( [LINK] ) The Value of Values ( this video ) All by Rich Hickey (Clojure creator) - strongest programming speaker I've found to date.
Leporello.js follows a pragmatic functional approach. You can use IO functions and throw exceptions as you typically would, without the need for an IO monad or an Option monad. However, there is one critical limitation – you cannot mutate your data structures. Mutations are not allowed because they would make time-travel debugging impossible. For instance, the following code is forbidden: const point = {x: 1, y: 2} point.x = 2 And instead you should use this: const point = {x: 1, y: 2} const another_point = {...point, x : 2} In Leporello.js, it's vital to avoid mutating data structures; instead, you create new ones. You can watch Rich Hickey's insightful talk [0], where he discusses the advantages of immutability in functional programming. In many ways, Leporello.js bears a resemblance to Clojure. Clojure served as a source of inspiration for Leporello.js, to the extent that I even contemplated building Leporello.js for Clojure first. [0] this video