It's Time to Get Good at Functional Programming

http://www.ddj.com/development-tools/212201710?cid=RSSfeed_DDJ_All

by Anon84 • 18 years ago

13 25 18 years ago

timr4• 18 years ago

"Most modern programming languages, including object-oriented languages, are imperative: A program is essentially a list of instructions intended to be executed in order."

That's silly. Anyone who has worked with a pure OO language knows that there's nothing inherently imperative about the approach. Just because the most popular OO languages (C++, Java) ultimately force you to have a main() doesn't mean that a procedure is required to write OO code. That's more a reflection of the OS execution model than the language used to write the app.

I've personally written CORBA apps that were asynchronous, distributed and multi-threaded -- in C++. Object-oriented development is more than capable of handling the complexity of multi-core processing.

dablya5• 18 years ago

But it's easier to program multi-threaded applications when the code doesn't produce side-effects...

gaius2• 18 years ago

It ought to be possible to structure an OO program so side effects can't escape their logical boundaries. But the only people who can do that are a) functional programmers and b) given the choice aren't using Java...

ricky_clarkson2• 18 years ago

Procedural does not mean "has a main()". It means that the code within a procedure (or method, or function) is always a sequence of steps, i.e., a procedure. OO is a procedural paradigm. doThis(that) is replaced by that.doThis().

dablya5• 18 years ago

Procedural separates procedures from state. OO combines state and functionality into objects. Also, http://en.wikipedia.org/wiki/Message_passing#OOP

timr4• 18 years ago

I'm aware of that. But then, every program is procedural at some level; show me a program that doesn't execute as a sequence of steps.

The point is, OO does not require that your code be executed any more sequentially than does a functional language.

biohacker42• 18 years ago

Functional languages are a red herring.

If you actually want to do something you still have to have side effects, and that's when all that Haskell-ish beauty goes out the window.

It is still absolutely worth it to learn functional programming, it will change the way you think, it will make a better programmer in non functional languages, but it won't solve the problems of side effects.

ricky_clarkson2• 18 years ago

You mean that no Haskell programs can do I/O? Given that I've written Haskell programs that do I/O, I'd guess you're wrong.

smanek• 18 years ago

He never said that. He just said the "Haskell-ish beauty goes out the window," which is arguably true.

In my (limited) experience, Haskell code to do I/O (i.e., Monads) isn't a pretty or elegant as purely functional Haskell code. A lot of Haskell's useful tricks (i.e., its beauty like the ridiculously strong type system or lazy evaluation) don't work on code with side effects.

gaius2• 18 years ago

Purely functional languages are a red herring. So-called impure languages however like OCaml can be enormously productive for certain classes of problem. As always, it's a matter of the right tool for the job. Too many people these days only have one tool, then every problem looks like your face.

davidw• 18 years ago

Time to ditch the 'tools' metaphor, IMO:

http://journal.dedasys.com/2007/12/12/programming-languages-...

Most programmers, realistically, don't use that many languages at any given time, and if they could use fewer, they probably would. The more territory a language covers, the better off it is... well, at least as long as it can do so relatively well.

jganetsk• 18 years ago

Agreed. Languages like OCaml are actually higher-order imperative languages. They have a very rich, expressive system of "values". A value can be a function value, partially un-curried, and closed over arbitrary data. They can also be data values but can be arbitrarily complex. How many languages let you say:

let tree = Node (Node (Leaf 3) (Leaf 4)) (Node (Leaf 7) (Leaf 8))

This value is constant, just like an integer or string constant in many languages. In other words, the right-hand side can be arbitrarily complex. And this data structure gets passed around in a very lightweight manner (by reference, not by copying).

The Java notion that values are either primitive, or objects... is limiting.

daniel_yokomizo• 18 years ago

1. Most lines of code don't require side-effects, the Haskell way just asks you to structure your program in pure parts and side effecting parts (usually 90/10). 2. Also it's easy to define your own forms of side effects and parameterize your code on them (so I write my code to depend on any monad m that offers references and the code runs using IO, ST or STM), not being constrained by whatever choices the language designers gave you initially 3. Monads (and arrows and other abstractions that can model side-effects) are beautiful by themselves. It's one of the most elegant ways to express, compose and restrict side-effects. In most languages there's no easy way to create different combinators to deal with side-effects, but in Haskell 'do', ';' and '<-' are only pieces of notation, the real meat is '>>=' and 'return' and whatever combinators you build upon these. 4. The Haskell way to deal with side effects is to use a pure language to build a side-effecting program. Instead of writing down the program you abstract its parts and use combinators to mix them. 'IO' is a value that can be manipulated not an action that was already executed.

jsmcgd• 18 years ago

Why do you think Clojure wasn't mentioned? Not mature enough?

13ren• 18 years ago

FP is the future of programming, and always will be.

The argument that many-core will lead to FP adoption used to appeal to me, but then I studied Erlang, and saw that its concurrency power was due to shared-nothing pure-message passing, and not due to it being functional. FP is a way to not need to share memory, but Erlang doesn't actually use that for concurrency. The thinking seems to be that inter-core communication should be coarser-grained (e.g. at the module level, not the level of recursion over a list), because it will always be slower than communication within a core.

Also, surprisingly to me, the over-hyped web services, SOA and ESB etc arguably also aim at pure-message passing concurrency.

It's Time to Get Good at Functional Programming

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