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I've been coding for a few years now, nothing too complicated. C++ is what I know best. I recently stumbled into Paul Graham's site, coding horror, and now here.
What do I learn to "enlighten myself with the ways" of functional programming? Haskell, Scheme or CLisp?
If you're interested in functional programming, Haskell is the only purely functional language on that list. Common Lisp is a weakly functional mixed-paradigm language, and Scheme is more strongly functional but still not pure. Lisps are interesting for other reasons, but Haskell is pretty much the state of the art for functional programming.
Incidentally, the reason I encourage more strongly functional languages like Haskell is because a large part of "learning functional programming" is learning how to think of your program in a different way. If your language makes it feel natural to write imperatively, it's too easy to fall into that way of thinking and never realize there's a different way to do it.
Of the three, I'd say Scheme is the simplest overall, if that's your main concern. SICP uses Scheme, and is itself a great resource for learning to program the functional way.
However, Common Lisp has many advanced features that make it quite expressive, such as powerful error handling (more powerful than exceptions), multimethods and support for aspect oriented programming.
You might start with one but, in the end, you should study many languages.
All three are good, depends on each person.
If you decide on haskell, this is a great ressource : learnyouahaskell and also real world haskell
As other answers say, all three are good.
But if you decide on Lisp, then I'd suggest you go for Clojure which is perhaps its most recent reincarnation.
'enlighten myself with the ways' of functional programming?
Haskell's the strongest exemplar of the functional style, emphasizing purely functional programming (no side effects), strong static typing, and with a pragmatic implementation with an emphasis on multicore parallelism, while also having a huge community (around 2000 libraries available on http://hackage.haskell.org , and many online resources).
It's somewhat famous for retraining how people think about programming.
But this is advocacy, and not a useful stackoverflow question and answer session. You'll have to decide for yourself what you're looking to learn.
Have you heard of F#, ML or OCaml? These three languages belong to the ML family.
F# is a new ML dialect supported by Microsoft and will be shipped with Visual Studio 2010. The good thing about F# (or other ML languages) is that when you first start you could write imperative code and learn good functional style gradually.
Here's an example I wrote for Project Euler #2. When I first did it, I used imperative style. Later on, I know how to use lazy sequence, which is a powerful functional programming concept.
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I already have a few languages under my belt (in a rough order of expertise): Python, C, C++, PHP, Javascript, Haskell, Java, MIPS, x86 assembler. But it's been almost 2 years since I learned a new one, and I'm starting to get the itch. I have a few criteria:
Must (repeat: must) have a free Linux implementation
Should be different from the languages I already know. In other words, it should have features that get me thinking about solving problems in a new way.
Should have some potential for practical use. It doesn't need to be the next Java, but this rules out Brainf* and Shakespeare :) I don't really care how many job postings does it have, but real-world apps and libraries are a plus.
Should have at least just enough free learning materials to get me started in it.
I was thinking Lisp (CL? something else?) or OCaml. I already have some experience with functional languages with Haskell (yes I know that Lisp/OCaml are multi-paradigm). I'm not an expert - e.g. parts of code from Real World Haskell can still contort my brain, but I understand the basic concepts and some advanced ones (functors, monads).
Which one to choose? Any other languages that I have overlooked? Also, could you please include some useful links to good books/tutorials etc.
Neither Lisp nor OCaml is super far afield from what you already know. Here are four suggestions chosen partly for intrinsic interest and partly to stretch your horizons.
A logic programming language, probably Prolog. I haven't found good materials online, but the book The Art of Prolog by Sterling and Shapiro is excellent. The more basic textbook by Clocksin and Mellish is also good. The main point of interest is programming with relations, not functions.
A pure object-oriented language, either
Smalltalk or Self. If you've only used hybrid object-oriented languages you'll be amazed how beautiful pure object-orientation can be. I've linked to the Squeak implementation of Smalltalk. I personally would recommend learning Smalltalk before tackling Self; there's a very large and active community and the software is well developed. Self stands on Smalltalk's shoulders and is an even more inspiring design, but the community is much smaller. For those who have access to the ACM Digital library I recommend the excellent talk by Dave Ungar at HOPL-III; the paper is also pretty good.
The Icon programming language has two great things going for it; a powerful and unusual evaluation model with implicit backtracking, and a user-extensible model of string processing that beats regular expressions all hollow. I'm sorry to say that Icon has never quite kept pace with the times, and of all my recommendations it is the least practical. In fact I fear the language is moribund. But it will stretch your mind almost as much as Haskell, and in wildly different directions. Icon is still very useful for string-processing tasks of modest size.
You can read about Icon string processing in an article by Ralph Griswold from Computer Journal.
The Lua programming language is my last and least radical suggestion. Its interest is not so much in novel language features or paradigms but in the superb engineering of the language and its implementation. Lua occupies a number of niches, including scripting, gaming, string processing, and lightweight functional programming. But its main point of interest is its seamless integration with C, and to get the full benefit, you should bind a C library into Lua.
The HOPL-III web site also contains an excellent talk and paper about Lua.
Both Common Lisp and Ocaml are certainly useful to learn. If you already know Haskell, CL might be the more different experience.
SBCL and Clozure CL are both very useful implementations of Common Lisp on Linux. (Overview about various implementations: Common Lisp survey.)
As a starting point I would recommend to use Peter Seibel's excellent book Practical Common Lisp, that is both available online and printed.
Community pointers are here: CLIKI.
Prolog may be what you are looking for.
Edit
The first commenter is right, my answer was pretty short and not very useful, so:
My preferred implementation is SWI-Prolog. I personally learned from Prolog Programming for Artificial Intelligence. It's style is pretty clear and it contains many examples, but I don't own any other book on logic programming (it's a shame, really :) so I have no basis for comparison.
Erlang is pretty interesting to learn because of its super efficient concurrency model, and the ease with which you can write distributed systems (for an example of this, CouchDB was written in Erlang). It's a dynamically typed functional language, but you can also write code in a procedural fashion. The tutorial I learned it with is called "Getting Started with Erlang", which covers just about every part of the language.
If you want to make use of your Java and functional programming knowledge, and you want to learn a Lisp, then try Clojure.
The implementation is free and cross-platform including Linux, because it runs on the JVM. Being a Lisp, it's different enough (in useful and wonderful ways) from most other languages to make things interesting. Some features such as immutable data structures, multimethods, metadata support, focus on safe concurrency, etc. are fairly novel compared to the languages you listed. Clojure is geared heavily toward being a practical and useful language rather than an academic one. It's a functional language but not "pure", which is arguably a good thing. You can also trivially make use of any Java library from within Clojure.
Clojure is a new language, so the only book out so far is Programming Clojure, but it's a pretty good one. There's also a wiki which may not be entirely up-to-date, because the language is still evolving very quickly. The mailing list and IRC channel are very friendly, welcoming places to ask questions. The official website is also a good resource, of course.
I'm going to recommend something that I haven't yet tried, but plan to, so you have to judge for yourself this one. There's this language, called IO, which is particular in that its prototype-based, like JavaScript, but also borrows concepts from many other languages. Its job market it's probably nonexistent, but I thought I mention this language.
Otherwise, a language from the Lisp family may be pretty different from what you already know. In that regard I'd recommend Scheme, which is, in my opinion, more elegant than Common Lisp. The new concept that you might found interesting in Scheme is continuations.
If you take the Scheme path, make some time to watch these videos from 1986. They're amazing.
Have a look at Smalltalk ! Either Cincom VWST or Smalltalk/X - dont bother with Squeak as the interface is terrible). VAST is good also but really only Windows centric. And dont bother about the sceptics that pore scorn on Smalltalk -- they arent using it and are stuck in the morass of edit-run-debug cycle languages and multiple dispirt linked libraries. :-)
Why these Smalltalks - well, they come complete wth excellent IDE, GUI tools builtin, best debugger you will ever see, online help, and is totally independent of the underlying OS. Eg a ST/X programming running under Linux can be transfered ( source code) to Windows ST/X and it should execute.
ST/X is free with only a very minor licience restrictions, Cincom offer a free NC ( Not Commercial ) version that is NOT restricted. I use ST/X as I prefer the default look & feel
it offers. Their IDE interfaces are very similar.
Languages without a IDE & GUI tools are just wasting your time as the world is really GUI, no matter how terrific the underlying language is. Eg Ruby is great, but with no IDE or easy GUI tools its really frustrating.
Smalltalk is not easy to get into, and its not perfect,(what language is?) but very satisfying to learn & use. And now that the hardware and operating systems have finally caught up with Smalltalks needs . very efficient.
I second Rainer's Common Lisp recommendation.
CL has all the things you're looking for and will provide a genuinely novel experience that will also make your coding efforts and approaches in other languages better.
But bring patience and persistence, you will have to grasp a lot of concepts that will seem alien at first.
You could try Tcl. It was sufficiently different to provoke an adverse reaction in my brain, so I can't really tell you how I found it different, but there's been a lot of good stuff written in it (maybe less nowadays than earlier).
C# has a free implementation in Linux under the Mono project, and it arguably is a very marketable skill unless you're completely anti-Microsoft.
My favorite C# book is Pro C# 2008 and the .NET 3.5 Platform, Fourth Edition.
If you're really want exotic, F# is an OCaml style language that runs on the .NET platform and mono, and is getting a lot of attention these days.
http://msdn.microsoft.com/en-us/fsharp/default.aspx
Books for F#:
http://www.amazon.com/s/ref=nb_ss_gw?url=search-alias%3Daps&field-keywords=f%23
Of the suggestions I've seen so far, I like Lisp (see Secko) and Smalltalk (see brett), as both will give you another view of languages. Prolog even more so.
Another language that is different is Erlang -- I haven't had a chance to learn it yet, but it handles concurrency in a different way. The best link I can give you is the main website.
In terms of recommendations, Lisp is good both because it is currently used and because it is very old. The others you will have to look at sources and see which one appeals the most.
Try FORTRAN, then? I hear it's still actively used by the scientific and mathemematical communities, plus it should be dissimilar enough to be a learning challenge.
Compilers:
http://gcc.gnu.org/wiki/GFortranBinaries
http://www.g95.org/
http://www.fortran.com/compilers.html
http://www.thefreecountry.com/compilers/fortran.shtml
IDEs:
http://www.eclipse.org/photran/
http://force.lepsch.com/ (FORTRAN 77 only)
Tutorials:
Introduction to Modern FORTRAN: http://www-uxsup.csx.cam.ac.uk/courses/Fortran/
FORTRAN 90 Tutorial: http://www.cs.mtu.edu/~shene/COURSES/cs201/NOTES/fortran.html
You could also learn Visual Basic.NET, in case you ever get forced to maintain that. Evidently mono has a working Linux implementation of it:
http://www.mono-project.com/Visual_Basic
Factor is pretty radically different from everything you said you know, and also everything else listed. It's stack-based, like Forth, but has a fairly comprehensive library and a lot of interesting features.
Ada is very practical -- there's a compiler based on gcc -- but also quite different from the other imperative languages you know. I find the type system a bit stifling, but it was worth learning something about.
Lisp is a great HLL, it has everything that other languages lack. In my opinion, this is a very good language that can "satisfy" any programmers needs.
Perl is also a HLL like Lisp, it's interesting and fun at the same time. It derives from C so you can pick it up as you go. It can be hard sometimes and some people tend to get lost while learning, but it's worth knowing.
Both languages are free of use and come with Linux.
Links
Lisp:
If Lisp is so great,
An Introduction and Tutorial for Common Lisp
Perl:
PERL -- Practical Extraction and Report Language
Books
On Lisp - Great book by Paul Graham on the Lisp language. It's free and you can download it here.
Scala has been very good for making me see programming in a new light. I haven't used it for anything worklike yet, but it's still affected how I write code in other languages - not just Java, but PHP. I recently wrote a simple parser for a WordPress plugin, and the code is vastly more functional and immutable than it would have been six months ago, and better for it, despite the lack of enforcement in PHP.
The only other language to have affected the way I work so dramatically is Perl, nearly a decade earlier. Perl has contributed a lot to the way I pseudo-code, even if I never touch the language itself.
Many people compare the functional aspects of Scala to Haskell. You may even imagine that knowing Haskell means you already know all Scala could teach you, but I don't believe that. The way Scala combines OO and function has a way of making it seem like that's actually the truest form of both of them.
Like you, I have over a dozen languages under my belt. While shopping for something to play with for writing a cross-compiler, I ran across ML and family. Many very good ideas there, and they have taught me to write code is a much different way; for example, my JavaScript now has a decidedly functional bent.
After toying with OCaml under Windows a while (and getting frustrated with stability issues), I ran across F#, an offspring of OCaml. The two are quite similar (can cross-compile a lot of code), but OCaml apparently has a really good macro system (P4) and type-classes (in support of writing "strongly typed" operators against generic types), while F# has excellent support for asynchronous and parallel operations, monads, units-of-measure for numeric types, as well as cleaner OO syntax and awesome IDE integration (VS2008 & will be released in-the-box with VS2010). I much prefer F# these days, since I have access to the whole .NET runtime and loads of 3rd party libraries. In fact, I write most of my one-off and utility code in F# now; for me, its generally much more productive than C++, JavaScript, C#, PowerShell, or anything else.
F# works fairly well under Mono on Linux, and has a good following there. The compiler and runtime will be open sourced once stable (released with VS2010), and the developers consider Mono support enough of a priority for it to be seriously considered for non-Microsoft use.
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I'm interested in compilers, interpreters and languages.
What is the most interesting, but forgotten or unknown, language you know about? And more importantly, why?
I'm interested both in compiled, interpreted and VM languages, but not esoteric languages like Whitespace or BF. Open source would be a plus, of course, since I plan to study and hopefully learn from it.
I love compilers and VMs, and I love Lua.
Lua is not as well supported as many other scripting languages, but from a mindset like yours I'm sure you will fall in love with Lua too. I mean it's like lisp, (can do anything lisp can as far as I know), has lots of the main features from ADA, plus it's got meta programming built right in, with functional programming and object oriented programming loose enough to make any type of domain language you might want. Besides the VM's code is simple C which means you can easily dig right into it to appreciate even at that level.
(And it's open-source MIT license)
I am a fan of the D programming language. Here is a wikipedia article and and intro from the official site.
Some snippets from the wikipedia article:
The D programming language, also known simply as D, is an object-oriented, imperative, multiparadigm system programming language by Walter Bright of Digital Mars. It originated as a re-engineering of C++, but even though it is predominantly influenced by that language, it is not a variant of C++. D has redesigned some C++ features and has been influenced by concepts used in other programming languages, such as Java, C# and Eiffel. A stable version, 1.0, was released on January 2, 2007. An experimental version, 2.0, was released on June 17, 2007.
on features:
D is being designed with lessons learned from practical C++ usage rather than from a theoretical perspective. Even though it uses many C/C++ concepts it also discards some, and as such is not strictly backward compatible with C/C++ source code. It adds to the functionality of C++ by also implementing design by contract, unit testing, true modules, garbage collection, first class arrays, associative arrays, dynamic arrays, array slicing, nested functions, inner classes, closures[2], anonymous functions, compile time function execution, lazy evaluation and has a reengineered template syntax. D retains C++'s ability to do low-level coding, and adds to it with support for an integrated inline assembler. C++ multiple inheritance is replaced by Java style single inheritance with interfaces and mixins. D's declaration, statement and expression syntax closely matches that of C++.
I guess a lot depends on what you mean by 'non-mainstream'.
Would lisp count as non-mainstream?
I would suggest having a look at Erlang - it's been getting a bit of press recently, so some of the learning resources are excellent. If you've used OO and/or procedural languages, Erlang will definitely bend your mind in new and exciting ways.
Erlang is a pure functional language, with ground-up support for concurrent, distributed and fault-tolerant programs. It has a number of interesting features, including the fact that variables aren't really variables at all - they cannot be changed once declared, and are in fact better understood as a form of pattern.
There is some talk around the blogosphere about building on top of the Erlang platform (OTP) and machine support for other languages like Ruby - Erlang would then become a kind of virtual machine for running concurrent apps, which would be a pretty exciting possibility.
I've recently fallen in love with Ocaml and functional languages in general.
Ocaml, for instance, offers the best of all possible worlds. You get code that compiles to executable native machine language as fast as C, or universally portable byte code. You get an interpreter to bring REPL-speed to development. You get all the power of functional programming to produce perfectly orthogonal structures, deep recursion, and true polymorphism. Atop all of this is support for Object-Orientation, which in the context of a functional language that already provides everything OOP promises (encapsulation, modularization, orthogonal functions, and polymorphic recyclability), means OOP that is forced to actually prove itself.
Smalltalk (see discussion linked here). Sort of the grand-daddy of the dynamic languages (with the possible exception of Lisp and SNOBOL). Very nice to work with and sadly trampled by Java and now the newer languages like Python and Ruby.
FORTH was a language designed for low level code on early CPU's. Its most notable feature was RPN stack based math operations. The same type of math used on early HP calculators. For example 1+2+3+4= would be written as 1, 2, 3, 4, + , +, +
Haskell and REBOL are both fascinating languages, for very different reasons.
Haskell can really open your eyes as a developer, with concepts like monads, partial application, pattern matching, algebraic types, etc. It's a smorgasbord for the curious programmer.
REBOL is no slouch either. It's deceptively simple at first, but when you begin to delve into concepts like contexts, PARSE dialects, and Bindology, you realize there's much more than meets the eye. The nice thing about REBOL is that it's much easier to get started with it than with Haskell.
I can't decide which I like better.
Boo targets the .NET framework and is open source. Inspired by Python.
Try colorForth.
PROLOG is a rule-based language with back-track functionality. You can produce very human-readable (as in prosa) code.
I find constraint languages interesting, but it is hard to know what constitutes forgotten or unknown. Here are some languages I know about (this is certainly not an exhaustive list of any kind):
Ciao, YAP, SWI-Prolog, and GNU Prolog are all Prolog implementations. I think they are all open source. Ciao, gnu prolog, and probably the others also, as is common in Prolog implementations, support other constraint types. Integer programming for example.
Mozart and Mercury are both, as I understand it, alternative logic programming languages.
Alice is more in the ML family, but supports constraint programming using the GECODE C++ library.
Drifting a little bit off topic....
Maude is an interesting term rewrite language.
HOL and COQ are both mechanized proof systems which are commonly used in the languages community.
Lambda-the-Ultimate is a good place to talk about and learn more about programming languages.
I would have to say Scheme, especially in it's R6RS incarnation.
Modula-2 is the non-mainstream language that I've found most interesting. Looks mainstream, but doesn't quite work like what we're used to. Inherits a lot from Pascal, and yet is different enough to provide interesting learning possibilities.
Have a look at Io at http://www.iolanguage.com/
or Lisaac at: https://gna.org/projects/isaac/
or Self at: http://self.sourceforge.net/
or Sather (now absolutly forgotten)
or Eiffel http://www.eiffel.com
Why here are a few reasons. Io is absolutly minimalistic and does not even have "control flow elements" as syntacit entities. Lisaad is a follow-up to Eiffel with many simplifications AFAIKT. Self is a followup to Smalltalk and Io has taken quite alot from Self also. The base thing is that the distinction between Class and Object has been given up. Sather is a anwer to Eiffel with a few other rules and better support for functional programming (right from the start).
And Eiffel is definitly a hallmark for statically typed OO-languages. Eiffel was the first langauge whith support for Design by contract, generics (aka templates) and one of the best ways to handle inheritance. It was and is one of the simpler languages still. I for my part found the best libraries for Eiffel.....
It's creator just has one problem, he did not accept other contributions to the OO field.....
Regards
I recently learned of the existence of Icon from this question.
I have since used it in answers to several questions. (1, 2, 3, 4)
It's interesting because of its evaluation strategy - it is the only imperative language I know that supports backtracking. It allows some nice succinct code for many things :)
Learning any language that requires you to rethink your programming habits is a must. A sure sign is the pace at which you skim through the documentation of a language's core (not library). Fast meaning fruitless here.
My short list would be, in my order of exposure and what were the concepts I learned from them:
Assembly, C: great for learning pointers and their arithmetic.
C++: same as C with an introduction to generics, as long as you can stand the incredibly verbose syntax.
Ruby/Lua: scripting languages, dynamically typed, writing bindings for existing C libraries.
Python/C#/Java: skipped, these languages look to me as a rehash of notions originating elsewhere with a huge standard library. Sure the whole packages are nice, but you won't learn new concepts here.
OCaml: type infererence done right, partial application, compiler infered genericity, immutability as a default, how to handle nulls elegantly.
Haskell: laziness by default, monads.
My €.02.
I can't believe Logo is so forgotten. Ok, it's Logo. Sort of like lisp, but with slightly uglier syntax. Although working with lists in Logo, one encounters the delightfully named 'butfirst' and 'butlast' operations. =P
ML. Learning it and using it forces you think differently about programming problems differently. It also grants one patience, in most cases. Most.
How about go? It's brand new, so it's unknown and not mainstream (yet).
It's interesting because the syntax looks like what happens after you put C and pascal into a jar and make 'em fight.
Well once it was called MUMPS but now its called InterSystems Caché
http://www.intersystems.com/cache/
First answer - Scheme. It's not too widely used, but definitely seems like a solid language to use, especially considering the robustness of DrScheme (which in fact compiles Scheme programs to native binary code).
After that - Haskell is incredibly interesting. It's a language which does lazy evaluation right, and the consequences are incredible (including such things as a one-line definition of the fibonnaci sequence).
Going more mainstream, Python is still not really widely accepted in the business circles, but it definitely should be, by now...
Ken Kahn's ToonTalk, a cartoon language with hard-core theoretic underpinnings:
http://www.toontalk.com/
Prograph: http://en.wikipedia.org/wiki/Prograph ... seems Prograph lives on as Marten:
http://andescotia.com/products/marten/
Self's IDE was/is a thing of beauty, talk about Flow (in the Csíkszentmihályi sense)...
Overall, though, I'd have to say Haskell is the most interesting, for the potential adavances in computing that it represents.
Harbour for dynamic type. Great opition to business apps.
Reia!
http://wiki.reia-lang.org/wiki/Reia_Programming_Language
It's Erlang made sense, it's beutifull and I'm in love. It's so unknown that it doesn't even have a wikipedia page!
The first major (non-BASIC) language that I learned was Dream Maker, from http://www.byond.com.
It's somewhat similar to C++ or Java, but it's largely pre-built for designing multiplayer online games. It's very much based on inheritance.
It's an intersting language especially as a starting language, it gets gratifying results quicker, and lets be honest, most people who are first learning to program are interested in one thing... games.
I find Factor, Oz and OCaml quite interesting. In fact, I have started using Factor for personal projects.
Rebol of course !
It's so simple but so powerfull learn it at http://reboltutorial.com
I've recently looked up a lot about Windows PowerShell.
While not necessarily just a language. It's an awesome shell that has a built-in scripting language. It's basically a super-beefed up command line shell.
Unlike Unix shells, where everything is string text (which definitely has it's benefits), PowerShell commands (cmdlets) use objects. It's based on the .Net framework so you guys who are familiar with that will have probably already figured out that anything PowerShell returns can be piped and the properties and methods of that object can be used. It's fun to say "everything is an object!" again just like when OOP was getting big.
Very neat stuff. For the first time, Windows is implementing some of the Unix command-line interface tools similar to grep and the whole bunch.
If you're interested in VMs, you should look at Parrot...There's a bunch of languages supported and that's pretty neat....
O'caml is a good language if you want to learn how to implement a compiler...
Lisp developed a set of interesting language features quite early on in the academic world, but most of them never caught on in production environments.
Some languages, like JavaScript, adapted basic features like garbage collection and lexical closures, but all the stuff that might actually change how you write programs on a large scale, like powerful macros, the code-as-data thing and custom control structures, only seems to propagate within other functional languages, none of which are practical to use for non-trivial projects.
The functional programming community also came up with a lot of other interesting ideas (apart from functional programming itself), like referential transparency, generalised case-expressions (ie, pattern-matching, not crippled like C/C# switches) and curried functions, which seem obviously useful in regular programming and should be easy to integrate with existing programming practice, but for some reason seem to be stuck in the academic world forever.
Why do these features have such a hard time getting adopted? Are there any modern, practical languages that actually learn from Lisp instead of half-assedly copying "first class functions", or is there an inherent conflict that makes this impossible?
Are there any modern, practical
languages that actually learn from
Lisp instead of half-assedly copying
"first class functions", or is there
an inherent conflict that makes this
impossible?
Why aren't lisp, haskell, ocaml, or f# modern?
You might just need to take it on yourself and look at them and realize that they are more robust, with libraries like java, then you'd think.
A lot of features have been adopted from functional languages to other languages. But vice versa -- (some) functional languages have objects, for example.
I suggest you try Clojure. Syntactically beautiful dialect, functional (in the ML sense), and fast. You get immutability, software transactional memory, multiversion concurrency control, a REPL, SLIME support, and an inexhaustible FFI. It's the Lisp (& Haskell) for the Business Programmer. I'm having a great time using it daily in my real job.
There is no known correlation between a language "catching on" and whether or not is has powerful, well researched, well designed features.
A lot has been said on the subject. It exists all over the place in technology, and also the arts. We know artist A has more training and produces works of greater breadth and depth than artist B, yet artist B is far more successful in the marketplace. Is it because there's a zeitgeist? Is is because artist B has better marketing? Is it because most people won't take the time to understand artist A? Maybe artist B is secretly awful and we should mistrust experts who make judgements about artists? Probably all of the above, to some degree or another.
This drives people who study the arts, and people who study programming languages, crazy.
Scala is a cool functional/OO language with pattern matching, first class functions, and the like. It has the advantage of compiling to Java bytecode and inter-operates well with Java code.
Common Lisp, used in the real-world albeit not wildely so, I guess.
Python or Ruby. See Paul Graham's thoughts on this in the question "I like Lisp but my company won't let me use it. What should I do?".
Scala is the absolute king of languages which have adopted significant academic features. Higher kinds, self types, polymorphic pattern matching, etc. All of these are bleeding-edge (or near to it) academic research topics that have been incorporated into Scala as fundamental features. Arguably, this has been to the detriment of the langauge's simplicity, but it does lead to some very interesting patterns.
C# is more mainstream than Scala, but it also has adopted fewer of these "out-there" functional features. LINQ is a limited implementation for Wadler's generalized list comprehensions, and everyone knows about lambdas. But for all that, C# (rightfully) remains a bit conservative in adopting research features from the academic world.
Erlang has recently gained renewed exposure not only through being used by Twitter, but also by the rise of XMPP driven messaging and implementations such as ejabberd. It sports many of the ideas coming from functional programming being a language designed with that in mind. Initially used to run Telephone switches and conceived by Ericson to run the first GSM networks. It is still around, it is fully functional (as a language) and used in many production environments.
Lua.
It's used as a scripting/extension language for a number of games (like World of Worcraft), and applications (Snort, NMAP, Wireshark, etc). In fact, according to an Adobe developer, Adobe's Lightroom is over 40% Lua.
The guys behind Lua have repeatedly listed Scheme and Lisp as major influences on Lua, and Lua has even been described as Scheme without the parentheses.
Have you checked out F#
Lot's of dynamic programming languages implement ideas from functional programming. The newer .Net languages (C# and VB) have what they call lambda's but these aren't side effect free.
It's not difficult combining concepts from functional programming and object oriented programming for example but it doesn't always make a lot of sense. Object oriented languages (try to) encapsulate state inside objects while functional languages encapsulate state inside functions. If you combine objects and functions in one language it gets harder to make sense of all this.
There have been a lot of languages that have combined these paradigms by just throwing them together (F#) and this can be usefull but I think we still need a couple of decades of playing with languages like this untill we can create a new paradigm that succesfully will combine the ideas from oo and functional programming.
C# 3.0 definitely does.
C# now has
Lambda Expressions
Higher Order Functions
Map / Reduce + Filter ( Folding?) to lists and all types which implement IEnumerable.
LINQ
Object + Collection Initializers.
The last two list items may not fall under proper functional programming, anyways the answer is C# has implemented many useful concepts from Lisp etc.
In addition to what was said, a lot of LISP goodness is based on guaranteed lack of side-effects and using built-in data structures. Both rarely hold in real world. ML is probably better functional base.
Lisp developed a set of interesting language features quite early on in the academic
world, but most of them never caught on in production environments.
Because the kind of people who manage software developers aren't the kinds of people who you can have an interesting chat comparing different language features with. Around 2000, I wanted to use LISP to implement XML-to-HTML transforms on our corporate website (this is around the time of Amazon implementing their backend in LISP). I didn't get to. This is mildly ironic seeing as the company I was working for made and sold a Common LISP environment.
Another "real-world" language that implements functional programming features is Javascript. Since absolutely everything has a value, then high-order functions are easily implemented. You also have other tenants of functional programming such as lambda functions, closures, and currying.
The features you refer to ("powerful" macros, the code-as-data thing and custom control structures) have not propagated within other functional languages. They died after Lisp taught us that they are a bad idea.
Modern functional languages (OCaml, Haskell, Erlang, Scala, F#, C# 3.0, JavaScript) do not have those features.
Cheers,
Jon Harrop.
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I see a lot of talk on here about functional languages and stuff. Why would you use one over a "traditional" language? What do they do better? What are they worse at? What's the ideal functional programming application?
Functional languages use a different paradigm than imperative and object-oriented languages. They use side-effect-free functions as a basic building block in the language. This enables lots of things and makes a lot of things more difficult (or in most cases different from what people are used to).
One of the biggest advantages with functional programming is that the order of execution of side-effect-free functions is not important. For example, in Erlang this is used to enable concurrency in a very transparent way.
And because functions in functional languages behave very similar to mathematical functions it's easy to translate those into functional languages. In some cases, this can make code more readable.
Traditionally, one of the big disadvantages of functional programming was also the lack of side effects. It's very difficult to write useful software without I/O, but I/O is hard to implement without side effects in functions. So most people never got more out of functional programming than calculating a single output from a single input. In modern mixed-paradigm languages like F# or Scala this is easier.
Lots of modern languages have elements from functional programming languages. C# 3.0 has a lot functional programming features and you can do functional programming in Python too. I think the reasons for the popularity of functional programming is mostly because of two reasons: Concurrency is getting to be a real problem in normal programming, because we're getting more and more multiprocessor computers; and the languages are getting more accessible.
I don't think that there's any question about the functional approach to programming "catching on", because it's been in use (as a style of programming) for about 40 years. Whenever an OO programmer writes clean code that favors immutable objects, that code is borrowing functional concepts.
However, languages that enforce a functional style are getting lots of virtual ink these days, and whether those languages will become dominant in the future is an open question. My own suspicion is that hybrid, multi-paradigm languages such as Scala or OCaml
will likely dominate over "purist" functional languages in the same way that pure OO language (Smalltalk, Beta, etc.) have influenced mainstream programming but haven't ended up as the most widely-used notations.
Finally, I can't resist pointing out that your comments re FP are highly parallel to the remarks I heard from procedural programmers not that many years ago:
The (mythical, IMHO) "average" programmer doesn't understand it.
It's not widely taught.
Any program you can write with it can be written another way with current techniques.
Just as graphical user interfaces and "code as a model of the business" were concepts that helped OO become more widely appreciated, I believe that increased use of immutability and simpler (massive) parallelism will help more programmers see the benefits that the functional approach offers. But as much as we've learned in the past 50 or so years that make up the entire history of digital computer programming, I think we still have much to learn. Twenty years from now, programmers will look back in amazement at the primitive nature of the tools we're currently using, including the now-popular OO and FP languages.
The main plus for me is its inherent parallelism, especially as we are now moving away from higher CPU clock frequency and towards more and more cores.
I don't think it will become the next programming paradigm and completely replace OO type methods, but I do think we will get to the point that we need to either write some of our code in a functional language, or our general purpose languages will grow to include more functional constructs.
Even if you never work in a functional language professionally, understanding functional programming will make you a better developer. It will give you a new perspective on your code and programming in general.
I say there's no reason to not learn it.
I think the languages that do a good job of mixing functional and imperative style are the most interesting and are the most likely to succeed.
I'm always skeptical about the Next Big Thing. Lots of times the Next Big Thing is pure accident of history, being there in the right place at the right time no matter whether the technology is good or not. Examples: C++, Tcl/Tk, Perl. All flawed technologies, all wildly successful because they were perceived either to solve the problems of the day or to be nearly identical to entrenched standards, or both. Functional programming may indeed be great, but that doesn't mean it will be adopted.
But I can tell you why people are excited about functional programming: many, many programmers have had a kind of "conversion experience" in which they discover that using a functional language makes them twice as productive (or maybe ten times as productive) while producing code that is more resilient to change and has fewer bugs. These people think of functional programming as a secret weapon; a good example of this mindset is Paul Graham's Beating the Averages. Oh, and his application? E-commerce web apps.
Since early 2006 there has also been some buzz about functional programming and parallelism. Since people like Simon Peyton Jones have been worrying about parallelism off and on since at least 1984, I'm not holding my breath until functional languages solve the multicore problem. But it does explain some of the additional buzz right about now.
In general, American universities are doing a poor job teaching functional programming. There's a strong core of support for teaching intro programming using Scheme, and Haskell also enjoys some support there, but there's very little in the way of teaching advanced technique for functional programmer. I've taught such a course at Harvard and will do so again this spring at Tufts. Benjamin Pierce has taught such a course at Penn. I don't know if Paul Hudak has done anything at Yale. The European universities are doing a much better job; for example, functional programming is emphasized in important places in Denmark, the Netherlands, Sweden, and the UK. I have less of a sense of what's happening in Australasia.
I don't see anyone mentioning the elephant in the room here, so I think it's up to me :)
JavaScript is a functional language. As more and more people do more advanced things with JS, especially leveraging the finer points of jQuery, Dojo, and other frameworks, FP will be introduced by the web-developer's back-door.
In conjunction with closures, FP makes JS code really light, yet still readable.
Cheers,
PS
Most applications are simple enough to be solved in normal OO ways
OO ways have not always been "normal." This decade's standard was last decade's marginalized concept.
Functional programming is math. Paul Graham on Lisp (replace Lisp by functional programming):
So the short explanation of why this
1950s language is not obsolete is that
it was not technology but math, and
math doesn’t get stale. The right
thing to compare Lisp to is not 1950s
hardware, but, say, the Quicksort
algorithm, which was discovered in
1960 and is still the fastest
general-purpose sort.
I bet you didn't know you were functional programming when you used:
Excel formulas
Quartz Composer
JavaScript
Logo (Turtle graphics)
LINQ
SQL
Underscore.js (or Lodash),
D3
The average corporate programmer, e.g.
most of the people I work with, will
not understand it and most work
environments will not let you program
in it
That one is just a matter of time though. Your average corporate programmer learns whatever the current Big Thing is. 15 years ago, they didn't understand OOP.
If functional programming catches on, your "average corporate programmers" will follow.
It's not really taught at universities
(or is it nowadays?)
It varies a lot. At my university, SML is the very first language students are introduced to.
I believe MIT teaches Lisp as a first-year course. These two examples may not be representative, of course, but I believe most universities at the very least offer some optional courses on functional programming, even if they don't make it a mandatory part of the curriculum.
Most applications are simple enough to
be solved in normal OO ways
It's not really a matter of "simple enough" though. Would a solution be simpler (or more readable, robust, elegant, performant) in functional programming? Many things are "simple enough to be solved in Java", but it still requires a godawful amount of code.
In any case, keep in mind that functional programming proponents have claimed that it was the Next Big Thing for several decades now. Perhaps they're right, but keep in mind that they weren't when they made the same claim 5, 10 or 15 years ago.
One thing that definitely counts in their favor, though, is that recently, C# has taken a sharp turn towards functional programming, to the extent that it's practically turning a generation of programmers into functional programming programmers, without them even noticing. That might just pave the way for the functional programming "revolution". Maybe. ;)
Man cannot understand the perfection and imperfections of his chosen art if he cannot see the value in other arts. Following rules only permits development up to a point in technique and then the student and artist has to learn more and seek further. It makes sense to study other arts as well as those of strategy.
Who has not learned something more about themselves by watching the activities of others? To learn the sword study the guitar. To learn the fist study commerce. To just study the sword will make you narrow-minded and will not permit you to grow outward.
-- Miyamoto Musashi, "A Book of Five Rings"
One key feature in a functional language is the concept of first-class functions. The idea is that you can pass functions as parameters to other functions and return them as values.
Functional programming involves writing code that does not change state. The primary reason for doing so is so that successive calls to a function will yield the same result. You can write functional code in any language that supports first-class functions, but there are some languages, like Haskell, which do not allow you to change state. In fact, you're not supposed to make any side effects (like printing out text) at all - which sounds like it could be completely useless.
Haskell instead employs a different approach to I/O: monads. These are objects that contain the desired I/O operation to be executed by your interpreter's toplevel. At any other level they are simply objects in the system.
What advantages does functional programming provide? Functional programming allows coding with fewer potentials for bugs because each component is completely isolated. Also, using recursion and first-class functions allows for simple proofs of correctness which typically mirror the structure of the code.
I don't think most realistic people think that functional programming will catch on (becomes the main paradigm like OO). After all, most business problems are not pretty math problems but hairy imperative rules to move data around and display them in various ways, which means it's not a good fit for pure functional programming paradigm (the learning curve of monad far exceeds OO.)
OTOH, functional programming is what makes programming fun. It makes you appreciate the inherent, timeless beauty of succinct expressions of the underlying math of the universe. People say that learning functional programming will make you a better programmer. This is of course highly subjective. I personally don't think that's completely true either.
It makes you a better sentient being.
I'd point out that everything you've said about functional languages, most people were saying about object-oriented langauges about 20 years ago. Back then it was very common to hear about OO:
* The average corporate programmer, e.g. most of the people I work with, will not understand it and most work environments will not let you program in it
* It's not really taught at universities (or is it nowadays?)
* Most applications are simple enough to be solved in normal IMPERATIVE ways
Change has to come from somewhere. A meaningful and important change will make itself happen regardless of whether people trained in earlier technologies take the opinion that change isn't necessary. Do you think the change to OO was good despite all the people that were against it at the time?
I must be dense, but I still don't get it. Are there any actual examples of small application's written in a functional language like F# where you can look at the source code and see how and why it was better to use such an approach than, say, C#?
F# could catch on because Microsoft is pushing it.
Pro:
F# is going to be part of next version of Visual Studio
Microsoft is building community for some time now - evangelists, books, consultants that work with high profile customers, significant exposure at MS conferences.
F# is first class .NET language and it's the first functional language that comes with really big foundation (not that I say that Lisp, Haskell, Erlang, Scala, OCaml do not have lots of libraries, they are just not as complete as .NET is)
Strong support for parallelism
Contra:
F# is very hard to start even if you are good with C# and .NET - at least for me :(
it will probably be hard to find good F# developers
So, I give 50:50 chance to F# to become important. Other functional languages are not going to make it in near future.
I think one reason is that some people feel that the most important part of whether a language will be accepted is how good the language is. Unfortunately, things are rarely so simple. For example, I would argue that the biggest factor behind Python's acceptance isn't the language itself (although that is pretty important). The biggest reason why Python is so popular is its huge standard library and the even bigger community of third-party libraries.
Languages like Clojure or F# may be the exception to the rule on this considering that they're built upon the JVM/CLR. As a result, I don't have an answer for them.
It seems to me that those people who never learned Lisp or Scheme as an undergraduate are now discovering it. As with a lot of things in this field there is a tendency to hype and create high expectations...
It will pass.
Functional programming is great. However, it will not take over the world. C, C++, Java, C#, etc will still be around.
What will come of this I think is more cross-language ability - for example implementing things in a functional language and then giving access to that stuff in other languages.
When reading "The Next Mainstream Programming Language: A Game Developer’s Perspective" by Tim Sweeney, Epic Games, my first thought was - I got to learn Haskell.
PPT
Google's HTML Version
Most applications can be solved in [insert your favorite language, paradigm, etc. here].
Although, this is true, different tools can be used to solve different problems. Functional just allows another high (higher?) level abstraction that allows to do our jobs more effectively when used correctly.
Things have been moving in a functional direction for a while. The two cool new kids of the past few years, Ruby and Python, are both radically closer to functional languages than what came before them — so much so that some Lispers have started supporting one or the other as "close enough."
And with the massively parallel hardware putting evolutionary pressure on everyone — and functional languages in the best place to deal with the changes — it's not as far a leap as it once was to think that Haskell or F# will be the next big thing.
It's catching on because it's the best tool around for controlling complexity.
See:
- slides 109-116 of Simon Peyton-Jones talk "A Taste of Haskell"
- "The Next Mainstream Programming Language: A Game Developer's Perspective" by Tim Sweeney
Check out Why Functional Programming Matters.
Have you been following the evolution of programming languages lately? Every new release of all mainstream programming languages seems to borrow more and more features from functional programming.
Closures, anonymous functions, passing and returning functions as values used to be exotic features known only to Lisp and ML hackers. But gradually, C#, Delphi, Python, Perl, JavaScript, have added support for closures. It's not possible for any up-and-coming language to be taken seriously without closures.
Several languages, notably Python, C#, and Ruby have native support for list comprehensions and list generators.
pioneered generic programming in 1973, but support for generics ("parametric polymorphism") has only become an industry standard in the last 5 years or so. If I remember correctly, Fortran supported generics in 2003, followed by Java 2004, C# in 2005, Delphi in 2008. (I know C++ has supported templates since 1979, but 90% of discussions on C++'s STL start with "here there be demons".)
What makes these features appealing to programmers? It should be plainly obvious: it helps programmers write shorter code. All languages in the future are going to support—at a minimum—closures if they want to stay competitive. In this respect, functional programming is already in the mainstream.
Most applications are simple enough to
be solved in normal OO ways
Who says can't use functional programming for simple things too? Not every functional program needs to be a compiler, theorem prover, or massively parallel telecommunications switch. I regularly use F# for ad hoc throwaway scripts in addition to my more complicated projects.
Wow - this is an interesting discussion. My own thoughts on this:
FP makes some tasks relatively simple (compared to none-FP languages).
None-FP languages are already starting to take ideas from FP, so I suspect that this trend will continue and we will see more of a merge which should help people make the leap to FP easier.
I don't know whether it will catch on or not, but from my investigations, a functional language is almost certainly worth learning, and will make you a better programmer. Just understanding referential transparency makes a lot of design decisions so much easier- and the resulting programs much easier to reason about. Basically, if you run into a problem, then it tends to only be a problem with the output of a single function, rather than a problem with an inconsistant state, which could have been caused by any of the hundreds of classes/methods/functions in an imparative language with side effects.
The stateless nature of FP maps more naturally to the stateless nature of the web, and thus functional languages lend themselves more easily to more elegant, RESTFUL webapps. Contrast with JAVA and .NET frameworks that need to resort to horribly ugly HACKS like VIEWSTATE and SESSION keys to maintain application state, and maintain the (occasionally quite leaky) abstraction of a stateful imperative language, on an essentially stateless functional platform like the web.
And also, the more stateless your application, the more easily it can lend itself to parallel processing. Terribly important for the web, if your website happens to get popular. It's not always straightforward to just add more hardware to a site to get better performance.
My view is that it will catch on now that Microsoft have pushed it much further into the mainstream. For me it's attractive because of what it can do for us, because it's a new challenge and because of the job opportunities it resents for the future.
Once mastered it will be another tool to further help make us more productive as programmers.
A point missed in the discussion is that the best type systems are found in contemporary FP languages. What's more, compilers can infer all (or at least most) types automatically.
It is interesting that one spends half the time writing type names when programming Java, yet Java is by far not type safe. While you may never write types in a Haskell programm (except as a kind of compiler checked documentation) and the code is 100% type safe.
I agree with the first point, but times change. Corporations will respond, even if they're late adopters, if they see that there's an advantage to be had. Life is dynamic.
They were teaching Haskell and ML at Stanford in the late 1990s. I'm sure that places like Carnegie Mellon, MIT, Stanford, and other good schools are presenting it to students.
I agree that most "expose relational databases on the web" applications will continue in that vein for a long time. Java EE, .NET, Ruby on Rails, and PHP have evolved some pretty good solutions to that problem.
You've hit on something important: It might be the problem that can't be solved easily by other means that will boost functional programming. What would that be?
Will massive multicore hardware and cloud computing push them along?
Because functional programming has significant benefits in terms of productivity, reliability and maintainability. Many-core may be a killer application that finally gets big corporations to switch over despite large volumes of legacy code. Furthermore, even big commercial languages like C# are taking on a distinct functional flavour as a result of many-core concerns. Side effects simply don't fit well with concurrency and parallelism.
I do not agree that "normal" programmers won't understand it. They will, just like they eventually understood OOP (which is just as mysterious and weird, if not more so).
Also, most universities do teach functional programming , many even teach it as the first programming course.
In addition to the other answers, casting the solution in pure functional terms forces one to understand the problem better. Conversely, thinking in a functional style will develop better* problem solving skills.
*Either because the functional paradigm is better or because it will afford an additional angle of attack.