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  • how does pipe work

    - by lego69
    hello, explain me please how exactly pipe works, for example I have this snippet of the code set line = ($<) while(${#line} != 0) if(${#line} == 5) then echo line | sort | ./calculate ${1} endif set line = ($<) end I need to choose all rows with 5 words and after sort it and after transfer, but I'm confused, how will it work, first of all 'while' will take all information and after that transfer it to sort, or every iteration 'while' will do sort? thanks in advance

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  • Examples of useful or non-trival dual interfaces

    - by Scott Weinstein
    Recently Erik Meijer and others have show how IObservable/IObserver is the dual of IEnumerable/IEnumerator. The fact that they are dual means that any operation on one interface is valid on the other, thus providing a theoretical foundation for the Reactive Extentions for .Net Do other dual interfaces exist? I'm interested in any example, not just .Net based.

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  • How can i uniquely identify users trying to open() a kernel module?

    - by user349072
    Dear Gurus, I'm working on a Kernel module and i'm trying to Uniquely identify each one of the users trying to open() the module ( can be either processes or threads ). what is the best way to identify them? is there an ID i can get from a system call? i wish to get all users in a list that specifies whether they're trying to open the module for read \ write and i need to know which one tried acting... many many thanks. in regards, IK

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  • Why is the software world full of status codes?

    - by David V McKay
    Why did programmers ever start using status codes? I mean, I guess I could imagine this might be useful back in the days when a text string was an expensive resource. WAYYY back then. But even after we had megabytes of memory to work with, we continued to use them. What possible advantage could there be for obfuscating the meaning of an error message or status message behind a status code?

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  • Functional languages targeting the LLVM

    - by Matthew
    Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics, covariance and contravariance, etc.) Scala is all of these, but only targets the JVM. F# (and to some extent C#) is most if not all of these, but only targets .NET. What similar language targets the LLVM?

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  • Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

    - by Alex R
    And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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  • Truly declarative language?

    - by gjvdkamp
    Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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  • How do i write tasks? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side. That part is really all you need to watch if any). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • How do i write task? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • Translate imperative control flow with break-s/continue-s to haskell

    - by dorserg
    Consider the following imperative code which finds the largest palindrome among products of 3-digit numbers (yes, it's the one of the first tasks from "Project of [outstanding mathematician of 18th century]" site): curmax = 0 for i in range(999,100): for j in range(999,100): if ((i*j) < curmax): break if (pal(i*j)): curmax = i*j break print curmax As I'm learning Haskell currently, my question is, how do you translate this (and basically any imperative construct that contains something more complex than just plain iteration, e.g. breaks, continues, temporary variables and all this) to Haskell? My version is maxpal i curmax | i < 100 = curmax | otherwise = maxpal (i-1) (innerloop 999) where innerloop j | (j < 100) || (p < curmax) = curmax | pal p = p | otherwise = innerloop (j-1) where p = i*j main = print $ maxpal 999 0 but this looks like we're still in imperative uglytown. So what could you advise, what are the approaches of dealing with such cases FP-style?

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  • Using MonadPlus in FRP.Reactive.FieldTrip

    - by ony
    I'm studying FRP at this moment through FieldTrip adaptor. And hit the problem with strange way of frames scheduling and integration. So now I'm trying to build own marker Event for aligning Behaviour stepping. So... flipflop :: Behavior String flipflop = stepper "none" (xflip 2) where xflip t0 = do t <- withTimeE_ (atTime t0) return "flip" `mplus` xflop (t+3) xflop t0 = do t <- withTimeE_ (atTime t0) return "flop" `mplus` xflip (t+2) txtGeom = ((uscale2 (0.5::Float) *%) . utext . show <$>) main = anim2 (txtGeom . pure flipflop) Questions is: Why this example leads to memory leak? Is there safe way to build sequence of events where each next one is scheduled depending on previous?

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  • First Come, First Served process scheduling

    - by user253530
    i have 4 processes: p1 - bursts 5, priority: 3 p2 - bursts 8, priority: 2 p3 - bursts 12, priority: 2 p4 - bursts 6, priority: 1 Assuming that all processes arrive at the scheduler at the same time what is the average response time and average turnaround time? For FCFS is it ok to have them in the order p1, p2, p3, p4 in the execution queue?

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  • Why did you decide "against" using Erlang?

    - by Zubair
    Have you actually "tried" (means programmed in, not just read an article on it) Erlang and decided against it for a project? If so, why? Also, if you have opted to go back to your old language, or to use another functional language like F#, Haskell, Clojure, Scala, or something else then this counts too, and state why.

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  • Does a good programmer need to have good spatial sense?

    - by lisa1234
    Do you need to have good spatial sense to be a good programmer? I have next to nothing of it (I think it has to do with the differing vision of my eyes). I've already coded quite little things but wonder if this interferes with the ability to 'imagine' the assembly of the code in case of a more complex program? Sorry for my english, I'm Austrian and not so used to write in English.. Thanks for your ansers..

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  • Is C really a subset of C++?

    - by Allopen
    What I mean is, can any C code be implemented via C++? Maybe just simply change a compiler? I know C is much more efficient and concise. But despite of these, can C++ used to implement all functions that are implemented by C?

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  • Socket php server not showing messages sent from android client

    - by Mj1992
    Hi I am a newbie in these kind of stuff but here's what i want to do. I am trying to implement a chat application in which users will send their queries from the website and as soon as the messages are sent by the website users.It will appear in the android mobile application of the site owner who will answer their queries .In short I wanna implement a live chat. Now right now I am just simply trying to send messages from android app to php server. But when I run my php script from dreamweaver in chrome the browser keeps on loading and doesn't shows any output when I send message from the client. Sometimes it happened that the php script showed some outputs which I have sent from the android(client).But i don't know when it works and when it does not. So I want to show those messages in the php script as soon as I send those messages from client and vice versa(did not implemented the vice versa for client but help will be appreciated). Here's what I've done till now. php script: <?php set_time_limit (0); $address = '127.0.0.1'; $port = 1234; $sock = socket_create(AF_INET, SOCK_STREAM, 0); socket_bind($sock, $address, $port) or die('Could not bind to address'); socket_listen($sock); $client = socket_accept($sock); $welcome = "Roll up, roll up, to the greatest show on earth!\n? "; socket_write($client, $welcome,strlen($welcome)) or die("Could not send connect string\n"); do{ $input=socket_read($client,1024,1) or die("Could not read input\n"); echo "User Says: \n\t\t\t".$input; if (trim($input) != "") { echo "Received input: $input\n"; if(trim($input)=="END") { socket_close($spawn); break; } } else{ $output = strrev($input) . "\n"; socket_write($spawn, $output . "? ", strlen (($output)+2)) or die("Could not write output\n"); echo "Sent output: " . trim($output) . "\n"; } } while(true); socket_close($sock); echo "Socket Terminated"; ?> Android Code: public class ServerClientActivity extends Activity { private Button bt; private TextView tv; private Socket socket; private String serverIpAddress = "127.0.0.1"; private static final int REDIRECTED_SERVERPORT = 1234; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); bt = (Button) findViewById(R.id.myButton); tv = (TextView) findViewById(R.id.myTextView); try { InetAddress serverAddr = InetAddress.getByName(serverIpAddress); socket = new Socket(serverAddr, REDIRECTED_SERVERPORT); } catch (UnknownHostException e1) { e1.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } bt.setOnClickListener(new OnClickListener() { public void onClick(View v) { try { EditText et = (EditText) findViewById(R.id.EditText01); String str = et.getText().toString(); PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true); out.println(str); Log.d("Client", "Client sent message"); } catch (UnknownHostException e) { tv.setText(e.getMessage()); e.printStackTrace(); } catch (IOException e) { tv.setText(e.getMessage()); e.printStackTrace(); } catch (Exception e) { tv.setText(e.getMessage()); e.printStackTrace(); } } }); } } I've just pasted the onclick button event code for Android.Edit text is the textbox where I am going to enter my text. The ip address and port are same as in php script.

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  • how to send classes defined in .proto (protocol-buffers) over a socket

    - by make
    Hi, I am trying to send a proto over a socket, but i am getting segmentation error. Could someone please help and tell me what is wrong with this example? file.proto message data{ required string x1 = 1; required uint32 x2 = 2; required float x3 = 3; } client.cpp ... // class defined in proto data data_snd; data data_rec; char *y1 = "operation1"; uint32_t y2 = 123 ; float y3 = 3.14; // assigning data to send() data_snd.set_x1(y1); data_snd.set_x2(y2); data_snd.set_x3(y3); //sending data to the server if (send(socket, &data_snd, sizeof(data_snd), 0) < 0) { cerr << "send() failed" ; exit(1); } //receiving data from the client if (recv(socket, &data_rec, sizeof(data_rec), 0) < 0) { cerr << "recv() failed"; exit(1); } //printing received data cout << data_rec.x1() << "\n"; cout << data_rec.x2() << "\n"; cout << data_rec.x3() << "\n"; ... server.cpp ... //receiving data from the client if (recv(socket, &data_rec, sizeof(data_rec), 0) < 0) { cerr << "recv() failed"; exit(1); } //printing received data cout << data_rec.x1() << "\n"; cout << data_rec.x2() << "\n"; cout << data_rec.x3() << "\n"; // assigning data to send() data_snd.set_x1(data_rec.x1()); data_snd.set_x2(data_rec.x2()); data_snd.set_x3(data_rec.x3()); //sending data to the server if (send(socket, &data_snd, sizeof(data_snd), 0) < 0) { cerr << "send() failed" ; exit(1); } ... Thanks for help and replies-

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  • Government Mandates and Programming Languages

    A recent SEC proposal (which, at over 600 pages, I havent read in any detail) includes the following: We are proposing to require the filing of a computer program (the waterfall computer program, as defined in the proposed rule) of the contractual cash flow provisions of the securities in the form of downloadable source code in Python, a commonly used computer programming language that is open source and interpretive. The computer program would be tagged in XML and required to be filed with the Commission as an exhibit. Under our proposal, the filed source code for the computer program, when downloaded and run (by loading it into an open Python session on the investors computer), would be required to allow the user to programmatically input information from the asset data file that we are proposing to require as described above. We believe that, with the waterfall computer program and the asset data file, investors would be better able to conduct their own evaluations of ABS and may be less likely to be dependent on the opinions of credit rating agencies. With respect to any registration statement on Form SF-1 (Section 239.44) or Form SF-3 (Section 239.45) relating to an offering of an asset-backed security that is required to comply with Item 1113(h) of Regulation AB, the Waterfall Computer Program (as defined in Item 1113(h)(1) of Regulation AB) must be written in the Python programming language and able to be downloaded and run on a local computer properly configured with a Python interpreter. The Waterfall Computer Program should be filed in the manner specified in the EDGAR Filer Manual. I dont see how it can be in investors best interests that the SEC demand a particular programming language be used for software related to investment data.  I have a feeling that investors who use computers at all already have software with which they are familiar, and that the vast majority of them are not running an open source scripting language on their machines to do their financial analysis.  In fact, I would wager that most of them are using tools like Excel, and if they really need to script anything, its being done with VBA in Excel. Now, Im not proposing that the SEC should require that the data be provided in Excel format with VBA scripts included so everyone can easily access the data (despite the fact that this would actually be pretty useful generally).  Rather, I think it is ill-advised for a government agency to make recommendations of this nature, period.  If the goal of the recommendation is to ensure that the way things work is codified in a transparent manner, than I can certainly respect that.  It seems to me that this could be accomplished without dictating the technology to use.  To wit: An Excel document could contain all of the data as well as the formulae necessary, and most likely would not require the end-user to install anything on their machine The SEC could simply create a calculator in the cloud such that any/all investors could use a single canonical web-based (or web service based) tool Millions of Java and .NET developers could write their own implementations You can read more about this issue, including the favorable position on it, on Jayanth Varmas blog. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How to introduce a computer illiterate 50-year old to programming [closed]

    - by sunday
    The other day my dad asked me a question that I would have never expected from him. "How can I learn C++?" My dad is turning 56 this year and computers are a distant concept for him. He doesn't know how to use a phone very well besides calling numbers (no speed dial or contacts); though he has started to learn computers a little better - to the point that he knows how to open the internet (in Windows) and browse around (and has successfully completed several job applications entirely on his own online, of which he was offered positions too). But still, these are too narrow-windowed experiences to mean much, really. While he may not have the background, my dad knows how to read. And I mean reading as a skill, not just an ability. He has little to no college education (financial problems, family, etc.) and was fortunate enough to finish high school, but still taught himself to become a master electrician and has been one for almost 30 years now. He did the same with guitar, learning to play at a very professional level and has been praised for his skill. In high school, he picked up a weight lifting book - and was the only person in his high school at the time to qualify officially as an "athlete" by national standards. In all cases, he just needed something to read. Something to teach him. He absorbs information like a sponge. I have no doubt in my dad's motivation or capability of doing this, so my general goal is simply: Get my dad into the world of computers, and get him on the road to programming. I strongly believe that once I get him through the fundamentals, his drive and reading skill will keep him going on this own. So I'm asking you all: where should I start with all this? And what are the best resources out there? Should I get him to start Linux instead of Windows? Is C++ a bad idea? Remember, he needs to (IMO) learn computers first, and then get that first grasp (the "Hello world" experience) of programming. For money's sake and at top preference, I'd like free online resources that he can read, but by all means any good suggestions in print or paid-for-online are welcome (that I could possibly look into later to purchase). And also, I intend to start him off with C++ (no Python, Java, etc.), because I know it the best and will be able to help him along the way with code. (I have minimal knowledge right now in other languages). Edit: I'm getting a lot of persistent suggestions to use Python. The only reason I wanted to do C++ is that I KNOW it and can be THERE when my dad needs help. My VERY FIRST exposure to programming ever was Java. I learned Java, and I got good at it. I open to other suggestions, but please provide an effective application of your suggestions. EDIT #2: I understand my approach/thinking/knowledge could be lacking here. I'm a sophomore level undergraduate CS major. If you don't agree with anything in my post, tell me why - give me ideas, information - that's why I'm asking in the first place. To narrow down my general goal to specific reachable goals.

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  • socket problem with MySQL

    - by Hristo
    This is a recent problem... MySQL was working and a couple of days ago I must have done something. I deleted MySQL and tried reinstalling using the .dmg file. The mysql.sock file never gets created and I get the following error messages: Hristo$ mysql Enter password: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/mysql/mysql.sock' (2) I also tried stopping Apache and installing but Apache gave me an error... I don't know if this is good or bad: Hristo$ sudo apachectl stop launchctl: Error unloading: org.apache.httpd I tried the MacPorts installation as well but the socket file still didn't get created. I don't really know what to do and I don't want to reinstall Snow Leopard and start from scratch :/ I also tried installing the 32-bit version and same deal. No luck. Finally... I tried doing the source installation but when I get to the configuration step, I get the following error: -bash: ./configure: No such file or directory The file is "mysql-5.1.47-osx10.6-x86_64.tar.gz" so I think it is the proper file for source installation and yes I have a 64 bit system. I don't know what to do anymore. Any ideas? Thanks, Hristo

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