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So I'm starting to get a feel for what sets functional programming apart from imperative programming. So like any good convert I'm looking at things with the Haskell hammer and trying to imagine how my embedded programming work could be shaped as appropriate nails for that tool.
So that got me thinking about this question. Is the embedded environment a special case of general computing in the eyes of functional programming or is it just another form of the general case? Is the challenge all in the IO? My embedded work usually entails about 90 - 95% peripheral IO work and the last little bit of stuff being what algorithm work I can fit onto it and still make it back to my IO in time. Does that sort of work make a functional program unsuited to my needs?
Finally, if there are any projects to embedded Haskell projects you could suggest, that'd be greatly appreciated. Thanks.
There are a number of promising projects for bringing functional programming to the embedded programming world.
It seems like a common approach is to take advantage of the type safety and other correctness features of but to abandon heavyweight runtime like ghc. As a result of abandoning the run time, you give up features like garbage collection. Instead, embedded Haskell projects use embedded DSL languages that output real time C code.
Embedded projects using mix C, C++ and Haskell code, rather than being pure functional projects. The C code produced from the Haskell code is not idiomatic C code so collaborators on the project typically need to be familiar with Haskell syntax to participate.
Galois's Copilot project is one the mode extensively documented embedded Haskell projects.
http://corp.galois.com/blog/2010/9/22/copilot-a-dsl-for-monitoring-embedded-systems.html
Copilot uses the Atom DSL which seems popular
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/atom-0.0.2
There is also a moderately active Google Group
https://groups.google.com/forum/#forum/fp-embedded
Personally I found Haskell.Atom quite lacking. It's not functional programming it's an EDSL in a functional language. You are limited to the constructs of that EDSL. No higher order functions, list comprehensions and all the other things that make functional programming so succinct and enjoyable. It may be fun for exceptionally small projects (like blinking a LED) but to me it seems the code you write (not only the generated C-code) will grow exponentially compared to the functionality it provides.
If you want to go the functional route I suggest reading this paper by Malcolm Wallace. It's a bit dated but at least it describes in quite a detail how to do low-level I/O, IRQ-handling and so on in a pure functional language (Gofer, a Haskell-dialect).
Update: There's also a quite new research project with the goal to make a functional systems programming language based on Haskell, Habit. Unfortunately it seems to exist mostly in theory.
What's the advantage, for someone who is not a theoretical computer scientist, of learning a purely functional language like Haskell or Erlang instead of an "impure" language with a strong functional component, like Python or version 2 of the D programming language? My arguments are as follows:
No paradigm is perfect. Languages that are single-paradigm, regardless of what paradigm that is, are very restrictive.
Python or D will ease you into functional programming while you get real work done. Haskell or Erlang will force you to learn functional style all at once before you can actually do anything of interest in them.
Edit: By "impure" functional languages, what I really mean is strongly multiparadigm languages w/ a functional flavor, not strongly functional languages with some non-functional abilities.
It all depends on what are trying to achieve. If your goal to write production code in a functional language - a 'pure' functional language can make it more difficult.
But if you are trying to learn new concepts, 'pure' language gives you the benefit of guarding where you are sliding off the mark of functional concepts. Once you have clear understanding of differences you can go to a mixed environments - like F#, but before that it is all too easy to slip to the OOP way of doing things and because of this miss the advantages of functional approach.
In some other thread I offered an opinion that a better way of learning F# is to start with let us say Haskell (and was voted down for this), but if you learn F# to do OOP than what's the point - stay with C#
You almost answered your own question:
Haskell or Erlang will force you to learn functional style all at once before you can actually do anything of interest in them.
Actually, depending on what you mean by 'of interest', you can be productive in Haskell in a week.
The main reason for anyone to learn Haskell (language theorists already know it, and other kinds of theorists are too busy proving theorems to be bothered with programming) is that learning Haskell will change the way you think about programming. Especially the type system, list comprehensions (stolen for Python—the highest form of praise), and programming with pattern matching. You will be able to use many of your new thoughts in all the programming you do. And Haskell will force you to think new thoughts in a way that other langauges won't.
Erlang is an honorable language but has nothing comparable to Haskell's type system.
If you like Paul Graham you can read more about this line of reasoning in his essay Beating the Averages, especially the part about the "Blub Paradox". Just substitute Haskell for Lisp :-)
You learn very little if your "new" language is just a slight permutation of what you already know. It's like asking, "Why learn Chinese when I can just get a dialect coach to teach me to speak with a Scottish brogue?" I guess it's fine if you enjoy speaking with a brogue, but you're not really expanding your expertise very much.
Learning a functional language teaches you a new way of looking at things. Impure or mixed-paradigm languages like OCaml are good as well, but it can be tempting to use the impure elements as a crutch to avoid having to look at the problem in a new way. No, functional languages are not a magic bullet, but they do have a lot of interesting benefits, and you're robbing yourself of those benefits if you learn a language that has a "functional components" but doesn't really work like a real functional language.
For example, in a pure functional language like Haskell, state is very carefully isolated from the rest of your program. This makes all sorts of optimizations trivial that are very hard in other languages. For example, state is the enemy of parallel processing. In Haskell, you can just look at a function's type and be 100% confident that it won't create any side effects.
This way of thinking in functions that work with immutable data structures something that a pure functional language can teach you. I'm not saying pure functional languages are "the best," but they have their benefits. It's another tool in your belt. And you won't get that tool by sticking with what's familiar.
Is Erlang purely functional? I honestly thought it wasn't.
I'm not an expert on this, so take my words with a grain of salt.
Side-effects prevent (or make more complicated) lots of optimizations, including parallelism. So, in theory, going pure functional should mean better optimization for faster code, although I'm not sure this is true in practice. Even if it does not, it might someday be... it will be fun if a purely functional language comes along which makes using up all the cores easy peasy.
Additionally, in a way, programming without side-effects makes for easier to understand programs.
Because only pure is declarative at the operational semantics level. Pure functional programming (i.e. eliminating accidental dependencies) is required for parallelism.
Also, without the immutability restriction, you won't be forced to think about how to do algorithms just as fast as they can be done in imperative, or how to model interaction with the real world without state spaghetti, using functional reactive programming.
Thus you won't be maximizing your skills for writing code that is maximally composable and extensible.
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I have read numerous time that learning a language such as Haskell, Lisp or Smalltalk will somehow make you a better programmer while you program in other languages.
Is there more than just anecdotal evidence for that claim?
Or is it just the way people rationalize having spend a lot of time learning a programming language that they will never use?
IMHO, it is all about learning a new programming paradigm. If you know Java and then C#, there's not much gain, once both of them have almost the same "type of programming".
But if you get to learn a functional language or dynamic, for instance, you're forced to think another way, and that will probably help you to program better in your favorite language.
It is something like: "It is so easy doing this in {different language you learned}. There must be a better way to do this in {language you already know}". And then you rethink, and build up a more elegant way to do this in {language you already know}.
I don't have any hard evidence, but I have really appreciated the different way of looking at problems that I have since learning lisp (the same goes for python and c).
The key isn't necessarily learning different languages though, I believe that the key is actually the different viewpoints that you gain by learning different programming styles.
Good examples are functional, imperative, object-oriented, etc. Also, there are common design differences is interpreted vs compiled languages; static vs dynamic typing, etc.
Although most people do a majority of their programming using a single style (most commonly OOP over the past few years), I think that all programmers should know multiple styles so that they are better able to see the shortfalls of their own style.
Can't shed much light on this in terms of programming languages, but it seems very similar to the "why learn a dead language?" argument that surrounds Latin, and much of the reasoning there can be applied here.
Programming is a way of thinking, not writing code in programming language X: that is "coding", not "programming".
By knowing at least something about more than just one programming language - preferably across different paradigms, so imperative/OOP/functional/logical - you train that way of thinking about problems outside the context of the specific details and quirks of language X.
I think this always improves your abilities to be(come) a better programmer tremendously.
A great side-effect of learning new languages is the potential for application in your existing language.
For instance, I'm a Java programmer and I took the time to learn my first functional language (Haskell). I was recently asked to learn Scala for an upcoming project. This is extremely easy since I understand the comcepts of guards, recursion, etc. from Haskell.
Deeply learning language just for learning language has too little benefits. If you have a lot of tasks and you don't know language that ideal for solving it then it is make sense to learn that language. Otherwise it is make sense to spend the time to become expert in languages you already know.
I don't know that there will have been much rigorous study regarding the benefits of multi-programming language exposure on overall programming ability, but I would argue that the studies regarding why learning a foreign human language (which you may never use in practice) is beneficial would in general hold equally well for studying foreign programming languages. The benefits ascribed often include improved cognitive abilities as well as improved understanding of one's native language.
here's some links to studies
anecdotally, I complained a great deal about taking COBOL, and have never really used it but was able to apply things I learned in that class at my first job.
If you give any credence to the Pragmatic Programming guys, consider their advice from page 14 of their first book:
Learn at least one new language every year. Different languages
solve the same problems in different ways. By learning several
different approaches, you can help broaden your thinking and avoid
getting stuck in a rut.
Some examples that come to mind:
Knowing C and having to deal with memory management and do-it-yourself data structures can help you understand performance issues when programming in a higher level language where those details are hidden from you.
Conversely, learning an OO language can affect your C programming - with, for example, the concept of Polymorphism prompting you to use function pointers in ways you might not have otherwise.
Learning a language where functions are first class objects that can be passed around can make you think of similar techniques in other languages, even if, in those other languages, you have to make the functions methods in objects that get passed around.
Learning about the way Erlang handles concurrency can make you rethink how much shared state you use between threads in other languages.
Any language that has a built-in feature you find useful can prompt you to implement your own version of that feature in another language that doesn't have it, and thus allow you to solve problems in ways you might not have thought of if you hadn't been exposed to the feature in the language that has it built-in.
Learning about Interfaces in Java can make you think about the benefits of precisely specifying your (small "i") interfaces in other languages that don't have them as a formal construct in a type system.
No doubt there are others.
Learning a language is not a binary event. If you are a decent programmer, you should be able to trust your own instincts as to whether a language offers you a new take on your craft.
Virtually every language worth considering these days can be downloaded and test-driven in a couple of minutes. So do it -- pick one and try it out.
There are a limited number of cases where this "laissez-faire" approach falls short. If you're a complete beginner, of course it doesn't work. When I first learned C, I had to have it beaten into me, but it did turn out to be worth it because it made me understand pointers, memory reference and dynamic allocation in a way I hadn't previously.
But if you know that much already, just poke around and look for a language that makes your lightbulb go on.
Different languages have different ways of implementing the same ideas. By learning new languages, you get a different perspective on how things can be accomplished, and can then use that knowledge to approach how you program in your current environment. Think about object oriented and functional programming. OO Programmers can learn a lot about parrellization from languages like C.
Learning a language, especially one that practices a new paradigm, is very beneficial for every programmer. For example learning Scheme will help someone understand functional programming. The programmer can later practice what he/she learned with other languages like C#. She can think of new ways of doing things.
Also, as languages evolve, it's high likely that the language you use will adopt some features of other languages. Having taught myself Ruby, I was able to grasp the changes in C# 3.0 much easier.
I think learning languages will always benefit you even if you don't use them again. I started playing with Ioke as an attempt to learn something experimental and because of it my JavaScript has improved because certain ideas have been cemented.
learning a new language will possibly give you new insights that you will try translate to your main language.
I don't think there will be any hard evidence--I think this is more of an intuitive thing. Learning a totally different language will help you look at things totally different. Or maybe it won't. In any case, what's the harm in learning something?
It's entirely subjective, but way back when, after taking an undergraduate course in Haskell, I did notice that my programming style in C became more 'Haskell-like' for a while; I used a lot of simple, recursive functions. I also noticed that this programming style seemed to yield some of the same benefits programming in Haskell had; bugs were fewer, code was easier to understand (albeit slower).
So, while learning another programming language may not make everyone a better programmer, it definitely was a learning experience for me, personally.
What are the benefits of learning mathematics or physics that you won't use, or the benefits of studying philosophy or dead tongues?
It's the intellectual achievement and the enlightenment what matters, you will be a wiser person with any new thing that you learn, no matter if they are programming languages, literature, role playing games... of course if it's related to your working field, then you'll actually find a use, sooner or later :-)
I spent some time studying clojure even though I knew I wouldn't use it in the near-term (mostly because I can't really deploy on the JVM).
It has concepts that aren't supported by the languages I use (C#/C/C++/Python/Perl) and I wanted to know what I was missing and also if it would be worth looking into libraries that purport to add these features.
Specifically, I'm very interested in understanding Lisp-style macros and the direct concurrency support. I also spent some time reading the implementation, specifically the datastructures, which was very educational -- good to see a quality implementation of persistent datastructures to learn how they work (and give you immutability without sacrificing much performance).
Bryond what has already been said, I really like new languages just because it can bring new interest to programming. You learn different ways to approach problems and the strengths/weaknesses of certain languages. It is something new to learn and any good programmer should be striving to always be learning new things. It mixes up your daily routine of possibly programming in the same language for years.
I also like what everyone has said about programming perspective.
Some good points have been made.
I would add that learning languages you won't use in production work can be of value
To better appreciate and absorb the arguments and methods in texts and papers that will improve programming ability in languages I do use for production work (e.g. MIX/MMIX for Knuth's Art of Computer Programming; RATFOR for Kernighan and Plauger's Software Tools; I still use some ALGOL-based syntax for some pseudocode although I never wrote runnable code in ALGOL outside University)
To be able to check or prototype programs that will be written in a different language (e.g. some routines for numerical computing in C can be quickly checked or scaled using languages that have appropriate functionality built in such as Fortran, Python or Haskell)
Learning a new language can give insight as to how it could be used to more easily solve problems that were put to one side because of time or complexity constraints.
So, I am writing some sort of a statistics program (actually I am redesigning it to something more elegant) and I thought I should use a language that was created for that kind of stuff (dealing with huge data of stats, connections between them and some sort of genetic/neural programming).
To tell you the truth, I just want an excuse to dive into lisp/smalltalk (aren't smalltalk/lisp/clojure the same? - like python and ruby? -semantics-wise) but I also want a language to be easily understood by other people that are fond of the BASIC language (that's why I didn't choose LISP - yet :D).
I also checked Prolog and it seems a pretty cool language (easy to do relations between data and easier than Lisp) but I'd like to hear what you think.
Thx
Edit:
I always confuse common lisp with Smalltalk. Sorry for putting these two langs together. Also what I meant by "other people that are fond of the BASIC language" is that I don't prefer a language with semantics like lisp (for people with no CS background) and I find Prolog a little bit more intuitive (but that's my opinion after I just messed a little bit with both of them).
Is there any particular reason not to use R? It's sort of a build vs. buy (or in this case download) decision. If you're doing a statistical computation, R has many packages off the shelf. These include many libraries and interfaces for various types of data sources. There are also interface libraries for embedding R in other languages such as Python, so you can build a hybrid application with a GUI in Python (for example) and a core computation engine using R.
In this case, you could possibly reduce the effort needed for implementation and wind up with a more flexible application.
If you've got your heart set on learning another language, by all means, do it. There are several good free (some as in speech, some as in beer) implementations of Smalltalk, Prolog and LISP.
If you're putting a user interface on the system, Smalltalk might be the better option. If you want to create large rule sets as a part of your application, Prolog is designed for this sort of thing. Various people have written about the LISP ephiphany that influences the way you think about programming but I can't really vouch for this from experience - I've only really used AutoLISP for writing automation scripts on AutoCAD.
At the risk of offending some, I have a hard time reconciling "easily understood by other people that are fond of the BASIC language" with any of the languages you mentioned. That's not intended as a criticism, but as an observation that each of the languages you mention has a style and natural idiom that's quite different from that of BASIC.
Smalltalk - pure OO from the ground up, usually (e.g. Squeak) coupled with an integrated environment that is simultaneously the IDE and the runtime. IOW you enter the Smalltalk VM and work inside it rather than just writing a text that is "source code".
LISP - much closer to functional programming (although with imperative overtones); the prefix notation is the first barrier to most people who "like" other languages, but the concept and use of macros is a much more substantial one.
Clojure - The combination of LISP, OO, and JVM integration makes this one even less BASIC-like.
Python and Ruby - I lump these together (at the risk of further annoying fans of either ;-) because they are both OO language with distinct notations that will take an outsider a bit of learning curve. The use of indentation-only for control nesting in Python and the Perl-like use of special characters in Ruby are often points of the complaint by newcomers. Although both can be written in an imperative style, that would be considered non-standard by seasoned users.
Prolog - This is the most unlike BASIC of all languages mentioned. All of the other languages you mentioned can be (ab)used in a semi-procedural style, but that is essentially impossible in Prolog. It requires a thorough understanding of, and comfort with, recursion to do anything non-trivial.
Code written with a "native accent" in essentially all of these languages (but especially Prolog, IMHO) will make use of idioms and concepts that are outside the norm for conventional BASIC programming. Put another way, if you pick one of these and then write code "with a BASIC accent" you've pretty much wasted the benefits that the language can offer.
I believe that all of them are worth learning for the concepts they can teach (or at least reinforce, depending on your background). But the similarity to Language X (for a wide range of values of X) is not what you'll get.
I can answer you partially
(aren't Smalltalk/Lisp/Clojure the same? - like python and ruby? -semantics-wise)
No, it is not. Smalltalk is OO language with message pass instead method calls. Lisp is Lisp ;-) It means truly functional language with the powerful macro system, OO support which is never seen in other languages (in CL) and many more features. Closure is Lisp-like language without many Lisp features but good integration to JVM. It's not supporting tail call optimization for example. And python or ruby are classic imperative OO languages with some limited functional ability. Note word limited. For example, Guido doesn't like functional programming and removed some functional features in version 2.5 and 2.6.
If you familiar with imperative procedural programming as in Python and you want to change your paradigm you should make your decision carefully.
Prolog is a very different language. It can be very hard to grasp, mainly because it relies heavily on recursion to do very basic tasks. If you are really willing then give it a go. It can be very powerful because it allows to expess relationships and solve complicated problems simply, typical examples are Towers of Hanoi or quicksort. It will change the way you think, which can be difficult if you are used to imperative languages.
If you're interested in Prolog then there's a free version of Visual Prolog available and the commercial version is reasonably priced.
It's a strong type offshoot of Prolog so isn't your classic implementation of the language, but has a respectable history - Borland marketed the DOS ancestor of it as Turbo-Prolog back in the late '80s.
It's also Windows only, but can be used to create standard Windows DLLs so you can link your code into a 'normal' windows programming language. I've never used the package in anger myself, but I did a couple of Prolog courses at Uni so have downloaded it from time to time to play with and look for possible uses and it looks solid enough. Might be just the set of cogs you're looking for.
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.