Simplicity Matters By Rich Hickey (Keynote at RailsConf 2012)

http://www.confreaks.com/videos/860-railsconf2012-keynote-simplicity-matters

by scottjad • 14 years ago

146 39 14 years ago

richhickey• 14 years ago

Slides are here: https://raw.github.com/richhickey/slides/master/simplicityma...

Thanks, great to see more material along the same lines as your Simple Made Easy talk. The concepts you outlined in that talk (and in this one) have made a tremendous impact on how I think about creating software. Can't thank you enough.

VeejayRampay• 14 years ago

Good stuff. Really enjoyed the video.

t_hozumi• 14 years ago

Thank you. Are there slides of "Hammock Driven Development"?

cageface6• 14 years ago

His emphasis on simplicity is welcome, but I'm not so sure I agree that simple hashes are the best choice for internal data representations. Exposing all the fields of any particular datatype to all clients seems to invite exactly the kind incidental "complecting" he decries.

Every non-trivial program is going to have to define abstract datatypes and I'm not sure how embedding and dispatching on a type tag in a hash is any better than using the more explicit support for dynamic dispatch you find in typical OO languages.

The real problem with most OO is that it mashes a lot of interdependent, mutable state together.

snprbob862• 14 years ago

> I'm not so sure I agree that simple hashes are the best choice for internal data representations

I've been contributing to the Clojure community lately. My experience working with hash-maps as the primary data structure has been entirely liberating.

At my startup, we've got an app with Sinatra services, a Rails API, a Node.js web frontend, and Backbone client code. JSON gets passed between them. Being forced to encode keys as strings is a mild annoyance that Clojure's reader syntax avoids, but the real issue is that I've got raw JSON, Javascript domain objects (Backbone.Model), Ruby models (ActiveRecord), and Ruby hashes (hashie/mash/similar). Each has their own idiosyncrasies and interfaces. Of all of them, the raw JSON is most pleasurable to work with. CoffeeScript & Underscore.js roughly approximate 10% of the awesomeness that is Clojure's core data structures, including maps, sets, vectors, and lazy-seqs.

ActiveRecord, for example, makes it super easy to tangle a bunch of objects up. If we had a big bag of functions, they could operate on in-memory hashes, or they could operate on database rows, or they could operate on the result of an API call. It would be so much simpler to reuse code between our main Rails API and our Sinatra service. And we could one-for-one translate functions for non-Ruby services. Instead of requiring a crazy tangled ness of polymorphism and mutable state.

> Every non-trivial program is going to have to define abstract datatypes

Absolutely true. However, Clojure has taught me that you really aught to only define a very small number of those. It's been said that it's much better to have 100 functions which operate on 1 data structures, than to have 10 functions that operate on 10. Clojure's get-in function for example: (get-in some-hash [:some :key :path]) is glorious compared to Ruby's some_hash[:some][:key][:path] because you don't need to go monkey patch in a get_path method. And even if you did monkey patch that in, it won't work for the some_object.some.key.path case, unless you got fancy with object.send and yet another monkey patch.

Look at some of the substantial pieces of Clojure code out there. They may only define a small handful of data structures, but most of those are even defined with defrecord, which produces a hash-like object, which all those 100s of functions work on. The rest are tiny primitives that compose in powerful an interesting ways.

> I'm not sure how embedding and dispatching on a type tag in a hash is any better than using the more explicit support for dynamic dispatch you find in typical OO languages

Because you may want differing dispatch & single-dispatch inheritance doesn't let you change your mind as easily. Those dynamic dispatches in Ruby/Python whatever are simply hash lookups anyway. You'll get the same performance either way. Look at the output of the ClojureScript compiler for example. Most code paths dispatch on :op, but you could just as easily dispatch on some bit of metadata, maybe the [:meta :dynamic] key path to have a function that runs differently on static vars than dynamic ones. People are also working on advanced predicate dispatch systems.

> The real problem with most OO is that it mashes a lot of interdependent, mutable state together.

That's a real problem. But it's not the real one :-)

cageface6• 14 years ago

That style of programming was also popular back in the pre-OO days with tagged unions in C. It's pretty easy to write fragile software that way that has a lot of incidental dependencies.

yoklov• 14 years ago

> CoffeeScript & Underscore.js roughly approximate 10% of the awesomeness that is Clojure's core data structures, including maps, sets, vectors, and lazy-seqs

There's always ClojureScript :)

espeed2• 14 years ago

Rich better illuminates these concepts in his "Simple Made Easy" talk (http://www.infoq.com/presentations/Simple-Made-Easy) at the Strange Loop conference, where he doesn't pull any OO punches.

bitops2• 14 years ago

I know that not everyone agrees with Rich, but I do think everyone who writes software professionally could benefit from watching this talk.

frou_dh• 14 years ago

And this one (2009):

http://www.infoq.com/presentations/Are-We-There-Yet-Rich-Hic...

SkyMarshal• 14 years ago

Thanks, was going to ask if this is worth watching if I've already watched his Strange Loop talk.

Jasber• 14 years ago

Has anyone watched both? Are they significantly different?

bitops2• 14 years ago

They are very different - one is geared towards more of an FP audience, the other targets the crowd at RailsConf.

cconroy• 14 years ago

It seems strange (to me)--maybe in a good way, but would it be preferable to use the JSON literal over the if statement (for the sake of the argument assume in javascript if returns a value)?

val = if (person === "Homer") { return expr } else if (person === "Bart") { return expr } ...

----

val = { "Homer": expr ,

"Bart": expr , ... }[person];

Would the literal be simpler because it uses data over syntax, or rules instead of conditionals?

lucian1900• 14 years ago

I frequently use the latter in Python. I like that it's easy to construct programatically (because it's data) and it more explicitly handles the various cases (especially the default case).

dpritchett• 14 years ago

Agree, I do it a lot as a way of selecting functions in a switch statement:

    handlers = {
        'dave'  : call_dave(),
        'ted'   : call_ted(),
        'julie' : contact('julie') }

    handlers['dave']()   # Call dave
    handlers['julie']()  # Contact julie

    [handlers[person]() for person in ['dave', 'julie', 'ted']] # Contact all three

tferris2• 14 years ago

"If you want everything to be familiar you'll never learn anything new—you have to break out of that."

tferris2• 14 years ago

"We can make the same exact software we are making today with dramatically simpler stuff—dramatically simpler languages, tools, techniques, approaches. Like really radically simpler—radically simpler than Ruby which seems simple.

Why aren't we?"

espeed2• 14 years ago

Inertia. That uncomfortable feeling you get when you venture into a new paradigm that you don't understand acts as a barrier and an excuse for people to stay where they are.

erichocean• 14 years ago

I'm not sure that's it. I do 100% consulting, and so end up working with lots of programmers.

In my experience, younger programmers who are otherwise competent tend to create the most complicated, generalized systems imaginable.

It's only when you get older, and have done enough systems, that you start to favor the "simple" approach Rich is talking about.

If I had to guess, I'd say that younger, more inexperienced programmers know there is a problem with complexity, and believe that "general", non-simple solutions are the way to tackle that complexity.

A similar thing happens with college students introduced to a new topic. They'll write these elaborate, complicated papers about the simplest of topics -- because they don't understand it well, and don't want to miss anything. It looks and feels very similar to what inexperienced developers do.

joske2• 14 years ago

I don't understand his point on encapsulation of information versus implementation. If anyone can help me here, I would be grateful.

* Should the user of your object/data have to make this distinction? Does he care if age is a piece of data or the result of a calculation?

* Should the user of your object/data know where a piece of information is? Suppose I start of with having a birthdate attribute in my person hash. I later read something about CQRS and decide to build my person as an event store. My birthdate is now in some event hash inside an events list in person. If I encapsulate this birthdate information, the users of my object/data don't have to change.

Encapsulating information/implementation might "complect" person, but doesn't it make it a lot more simple for the users/callers?

wandybrad• 14 years ago

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Simplicity Matters By Rich Hickey (Keynote at RailsConf 2012)

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