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  • Pure functional bottom up tree algorithm

    - by Axel Gneiting
    Say I wanted to write an algorithm working on an immutable tree data structure that has a list of leaves as its input. It needs to return a new tree with changes made to the old tree going upwards from those leaves. My problem is that there seems to be no way to do this purely functional without reconstructing the entire tree checking at leaves if they are in the list, because you always need to return a complete new tree as the result of an operation and you can't mutate the existing tree. Is this a basic problem in functional programming that only can be avoided by using a better suited algorithm or am I missing something?

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  • Program LED with just USB port

    - by LifeH2O
    I want to control LED with C# using only USB port. I don't want to attach any other device with USB. I just want to attach LED directly to USB port pins and program it (blink etc). How can i do that? I am new to hardware programming and it will be my first program. EDIT: I can do it already (blink LED) using printer port by attaching one led pin to data pin and other to ground. How can i do the same with USB port? My motherboard does not have a printer port. USB is the only option.

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  • How to create a language these days?

    - by Mike
    I need to get around to writing that programming language I've been meaning to write. How do you kids do it these days? I've been out of the loop for over a decade; are you doing it any differently now than we did back in the pre-internet, pre-windows days? You know, back when "real" coders coded in C, used the command line, and quibbled over which shell was superior? Just to clarify, I mean, not how do you DESIGN a language (that I can figure out fairly easily) but how do you build the compiler and standard libraries and so forth? What tools do you kids use these days?

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  • What to do when you are a programmer and have a cold?

    - by Zak
    If you have a cold that isn't too bad, does it make sense to still go into the office and get some coding done? Assume a private office, no meetings for the day, and you have some documentation and coding tasks that need to get done. Also assume that you operate on a PTO system, where all days off are "vacation" or PTO. To clarify, should one just not code at all when under the weather? That's what I'm getting at. Will you just kick yourself in your own rear when you go back to deal with code you wrote when you are sick? What is the error defect rate of sick vs non-sick programming hours?

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  • Is it easier to write filesystem drivers in userspace than in kernel space?

    - by Jack
    I will use the Linux NTFS driver as an example. The Linux kernel NTFS driver only has very limited write support in the kernel, and after 5 years it is still considered experimental. The same development team creates the ntfsmount userspace driver, which has almost perfect write support. Likewise, the NTFS-3G project which is written by a different team also has almost perfect write support. Why has the kernel drive taken so much longer? Is it much harder to develop for? Saying that there already exists a decent userspace application is not a reason why the kernel driver is not compelte. NOTE: Do not migrate this to superuser.com. I want a programing heavy answer, from a programming perspective, not a practical use answer. If the question is not appropriate for SO, please advise me as to why so I can edit it so it is.

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  • Is a function kind of like a static method?

    - by lkm
    I'm a java programmer and am trying to understand the difference between a method (java methods) and a function (such as in c++). I used to think that they are the same, just different naming conventions for different programming languages. But now that I know they are not, I am having trouble understanding the difference. I know that a method relates to an instance of a class and has access to class data (member variables), while a function does not (?). So is a function kind of like a static method? See here for explanations I read which led me to think this.

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  • What is the weirdest language you have ever programmed in?

    - by sfoulk526
    For me, it was Forth, way back at the end of the eighties! Yes, almost prehistory. But I was an un-degree-ed programmer, unable to afford college, self-taught C and Assembly, and not enough experience to open doors. I was invited to work in software engineering, my dream job by the engineering manager of my company, but...I had to do it in Forth, and the company was willing to teach me. The position was my start into embedded systems programming, and man did I learn a lot! Like, just how easy C and Assembly language REALLY could be! But it was a good journey, and though I never coded again in Forth, my fear of not being able to learn C and Assembly proficiently disappeared... ;-)

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  • What will be the value of i in the following pseudocode?

    - by user283403
    I got this question in a programming test. Do you think this question is even correct? Look at the answer choices. (2^x means 2 raised to x) Consider the following pseudocode. x := 1; i := 1; while (x = 1000) begin x := 2^x; i := i + 1; end; What is the value of i at the end of the pseudocode? a) 4 b) 5 c) 6 d) 7 e) 8 I am sure that the value of i will 1. I told the examiner of the discrepancy and he advised me the leave the question unanswered if I felt it was incorrect. What else could I have done?

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  • How to create a Windows GUI with a file explorer window, allowing users to choose files?

    - by Badri
    Here's what I want to do. I want to present a file explorer, and allow the user to select files, and list the selected files below. (I then want to process those files but that's the next part) For example, the way CD Burning softwares work. I have created a mock up here http://dl.dropbox.com/u/113967/Mockup.png As you can see, the left frame has a directory structure, the right frame has a file selected, and the bottom frame shows the selected file. What framework can I go about creating this? I am familiar with command line C++ stuff, but I haven't ventured into any GUI programming, and figured this idea would be a good place to start. Any suggestions on where to start?

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  • How do I change careers to become a programmer without spending a lot of money

    - by bgc83
    I'm currently a network engineer, but find myself wanting to get into the world of development. I took a little bit of Java in college, am 27 years old and have been network engineering for 4 years now. I have a mortgage and student loans so going back to school would be difficult. I'm willing to put in however much hardwork is needed around my full time job to learn, but part of me feels I may need actuall schooling to get down some of the advanced concepts. Just looking for a little advice and direction. I have purchased a bunch of the Head First programming books and have begun reading through some of them as I figure out my way into this transition.

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  • Given a number N, find the number of ways to write it as a sum of two or more consecutive integers

    - by hilal
    Here is the problem (Given a number N, find the number of ways to write it as a sum of two or more consecutive integers) and example 15 = 7+8, 1+2+3+4+5, 4+5+6 I solved with math like that : a + (a + 1) + (a + 2) + (a + 3) + ... + (a + k) = N (k + 1)*a + (1 + 2 + 3 + ... + k) = N (k + 1)a + k(k+1)/2 = N (k + 1)*(2*a + k)/2 = N Then check that if N divisible by (k+1) and (2*a+k) then I can find answer in O(N) time Here is my question how can you solve this by dynamic-programming ? and what is the complexity (O) ? P.S : excuse me, if it is a duplicate question. I searched but I can find

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  • In which language the KIS application might have been developed??

    - by Jeba
    Hello all, I just went through this link http://www.pcauthority.com.au/Feature/91093,the-tsar-of-antivirus.aspx and found that it's developed using c/c++ and visual studio with a little assembly language support. As a programmer i just want to know in what programming language the kaspersky internet security User Interface(UI) has been developed? Might be using QT(coz. of c++)? or using MFC(coz. of visual studio)?? With side tab like thing the UI looks good. Expecting the answers from expert analysts.

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  • Clojure for a lisp illiterate

    - by dbyrne
    I am a lifelong object-oriented programmer. My job is primarily java development, but I have experience in a number of languages. Ruby gave me my first real taste of functional programming. I loved the features Ruby borrowed from the functional paradigm such as closures and continuations. Eventually, I graduated to Scala. This has been a great way to gradually learn to approach non-trivial problems in a functional manner. Now I am interested in Clojure. I know all the sexy features that make it enticing (software transactional memory, macros, etc.), but I just can't get used to "thinking in lisp". I've seen Rich Hickey's screencasts aimed at java programmers, but they are geared towards explaining language features and not approaching real world problems. I am looking for any advice or resources which have made this transition easier for others.

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  • Write the longest possible loop.

    - by Abhay
    Hello Group, Recently I was asked this question in a technical discussion. What is the longest possible loop that can be written in a programming language? This loop has to be as long as possible and yet not an infinite loop and should not end-up crashing the program (Recursion etc...) I honestly did not know how to attack this problem, so I asked him if is it practically possible. He said using some computer science concepts, you can arrive at a hypothetical number which may not be practical but nevertheless it will still not be infinite. Anyone here; knows how to analyse / attack this problem. P.S. Choosing some highest limit for a type that can store the highest numerical value is apparently not an answer. Thanks in advance,

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  • Is there a way of providing a final transform method when chaining operations (like map reduce) in underscore.js?

    - by latentflip
    (Really strugging to title this question, so if anyone has suggestions feel free.) Say I wanted to do an operation like: take an array [1,2,3] multiply each element by 2 (map): [2,4,6] add the elements together (reduce): 12 multiply the result by 10: 120 I can do this pretty cleanly in underscore using chaining, like so: arr = [1,2,3] map = (el) -> 2*el reduce = (s,n) -> s+n out = (r) -> 10*r reduced = _.chain(arr).map(map).reduce(reduce).value() result = out(reduced) However, it would be even nicer if I could chain the 'out' method too, like this: result = _.chain(arr).map(map).reduce(reduce).out(out).value() Now this would be a fairly simple addition to a library like underscore. But my questions are: Does this 'out' method have a name in functional programming? Does this already exist in underscore (tap comes close, but not quite).

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  • Best solution to wait for all ajax callbacks to be executed

    - by glaz666
    Hi! Imagine we have to sources to be requested by ajax. I want to perform some actions when all callbacks are triggered. How this can be done besides this approach: (function($){ var sources = ['http://source1.com', 'http://source2.com'], guard = 0, someHandler = function() { if (guard != sources.length) { return; } //do some actions }; for (var idx in sources) { $.getJSON(sources[idx], function(){ guard++; someHandler(); }) } })(jQuery) What I don't like here is that in this case I can't handle response failing (eg. I can't set timeout for response to come) and overall approach (I suppose there should be a way to use more power of functional programming here) Any ideas? Regards!

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  • Tips for measuring the parallelism speed-up in multi-core development.

    - by fnCzar
    I have read many of the good questions and answers around multi-core programming how-tos etc. I am familiar with concurrency, IPC, MPI etc but what I need is advice on how to measure speed-up which will help in making a business case of spending the time to write such code. Please don't answer with "well run it with single-core code then multi-core code and figure out the difference". This is neither a scientific nor a reliable way to measure performance improvement. If you know of tools that will do some of the heavy lifting please mention them. Answers pertaining to methodology will be more fitting but listing tools is ok as well.

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  • Can you use #defined values in if statements (In C programs)?

    - by Jordan S
    I am new at C programming. I thought when you type something like #define Const 5000 that the compiler just replaces every instance of Const with 5000 at compile time. Is that wrong? I try doing this in my code and I get a syntax error. Why can't i do this? #define STEPS_PER_REV 12345 ... in some function if(CurrentPosition >= STEPS_PER_REV) { // do some stuff here } The compiler complains about the if statement with a syntax error that gives me no details.

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  • How to evaluate text strings provided by sed/grep/whatever?

    - by T.J.
    This is for UNIX shell programming. It have to be supported by multiple UNIX platforms including Solaris, Linux, and AIX. I have this scenario -- I am to read from a text file a string that may or may not contain an environment variable that may or may not be defined. For example: <foo.bar> This error code was found: $(error_code) I have the following code: statement=$(sed -n $1'p' $messagefile) echo $echo_flag $statement $1 = line number supplied to this particular function/script. $messagefile = filename of log file. $echo_flag = "-e" in Linux, otherwise, empty. $(error_code) = 42. Instead of getting this when running: <foo.bar> This error code was found: 42 I still get this: <foo.bar> This error code was found: $(error_code) How exactly do I tell the shell script that the value of statement should be evaluated further beyond what sed have done?

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  • client-server application design

    - by nelly
    Hi, i want to create a client-server application using sockets on .net platform and being new to networking programming and i have a dilemma. The client will send data to server often and also the server will notify clients often. What is the best way to design it? should the server keep a thread to communicate with each client until it quits or just the clients send data to the server and it update the clients regularly(few seconds) or none of those? Some help would be great. Thanks guys.

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  • Experiences teaching or learning map/reduce/etc before recursion?

    - by Jay
    As far as I can see, the usual (and best in my opinion) order for teaching iterting constructs in functional programming with Scheme is to first teach recursion and maybe later get into things like map, reduce and all SRFI-1 procedures. This is probably, I guess, because with recursion the student has everything that's necessary for iterating (and even re-write all of SRFI-1 if he/she wants to do so). Now I was wondering if the opposite approach has ever been tried: use several procedures from SRFI-1 and only when they are not enough (for example, to approximate a function) use recursion. My guess is that the result would not be good, but I'd like to know about any past experiences with this approach.

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  • Javascript: best solution to wait for all ajax callbacks to be executed

    - by glaz666
    Hi! Imagine we have to sources to be requested by ajax. I want to perform some actions when all callbacks are triggered. How this can be done besides this approach: (function($){ var sources = ['http://source1.com', 'http://source2.com'], guard = 0, someHandler = function() { if (guard != sources.length) { return; } //do some actions }; for (var idx in sources) { $.getJSON(sources[idx], function(){ guard++; someHandler(); }) } })(jQuery) What I don't like here is that in this case I can't handle response failing (eg. I can't set timeout for response to come) and overall approach (I suppose there should be a way to use more power of functional programming here) Any ideas? Regards!

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  • Does the Internet make us less good programmers? [closed]

    - by stagas
    With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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  • Instantiating Java object with a passed in method

    - by superluminary
    It's been a few years since I've been heavily into Java. Coming back to it I'm seeing this pattern all over the place: ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) { // do work } }); This looks more like Functional programming to me. It's a nice pattern but how is it possible to pass a method like this? In the old days a class was a class, and once compiled there was little you could do to it. My questions are: Can anyone let me know what this pattern is called? How can I write a class that can be instantiated in this way. Are there any other useful examples of functional patterns that have made their way into Java? What do I need to Google to read more about this? Thanks.

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  • Interesting or unique types encountered?

    - by user318904
    What is the most strange or unique type you have seen in a programming language? I was thinking the other day about a "random variable", ie whenever it is evaluated it yields a random value from some domain. It would require some runtime trickery. Also I bet there can be some interesting mapping of regular expressions into a type system. It does not necessarily have to be a built in or primitive type, but some random class that implements a domain specific type won't really be interesting just unique.

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