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  • scripting in awk

    - by benjamin button
    I have a text file with contents as below: 1,A,100 2,A,200 3,B,150 4,B,100 5,B,250 i need the output as : A,300 B,500 the logic here is sum of all the 3rd fields whose 2nd field is A and in the same way for B how could we do it using awk?

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  • Effects of the `extern` keyword on C functions

    - by Elazar Leibovich
    In C I did not notice any effect of the extern keyword used before function declaration. At first I thougth that when defining extern int f(); in a single file forces you to implement it outside of the files scope, however I found out that both extern int f(); int f() {return 0;} And extern int f() {return 0;} Compiles just fine, with no warnings from gcc. I used gcc -Wall -ansi, he wouldn't even accept // comments. Are there any effects for using extern before function definitions? Or is it just an optional keyword with no side effects for functions. In the latter case I don't understand why did the standard designers chose to litter the grammar with superfluous keywords. EDIT: to clarify, I know there's usage for extern in variables, but I'm only asking about extern in functions.

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  • How to start the web cam by programmatically?

    - by Nitz
    Hello Guys How to start any web cam through programmatically? my main requirement is it should start webcam? and that should be any application - software not a website. we can use any language. So how can start the web cam using programing language? btw... [I am not talking about the power of the webcam][Any web cam means any companies web cam]

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  • Beginner question: What is binding?

    - by JDelage
    Hi, I was trying to understand the difference between early and late binding, and in the process realized that the concept of binding is nebulous to me. I think I understand that it relates to the way data-as-a-word-of-memory is linked to type-as-a-set-of-language-features but I am not sure those are the right concepts. Also, how does understanding this deeply help people become better programmers? Please note: This question is not "what is late v. early binding" or "what are the trade-offs between the 2". Those already exist here. Thanks, JDelage

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  • Are there any modern platforms with non-IEEE C/C++ float formats?

    - by Patrick Niedzielski
    Hi all, I am writing a video game, Humm and Strumm, which requires a network component in its game engine. I can deal with differences in endianness easily, but I have hit a wall in attempting to deal with possible float memory formats. I know that modern computers have all a standard integer format, but I have heard that they may not all use the IEEE standard for floating-point integers. Is this true? While certainly I could just output it as a character string into each packet, I would still have to convert to a "well-known format" of each client, regardless of the platform. The standard printf() and atod() would be inadequate. Please note, because this game is a Free/Open Source Software program that will run on GNU/Linux, *BSD, and Microsoft Windows, I cannot use any proprietary solutions, nor any single-platform solutions. Cheers, Patrick

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  • More FP-correct way to create an update sql query

    - by James Black
    I am working on access a database using F# and my initial attempt at creating a function to create the update query is flawed. let BuildUserUpdateQuery (oldUser:UserType) (newUser:UserType) = let buf = new System.Text.StringBuilder("UPDATE users SET "); if (oldUser.FirstName.Equals(newUser.FirstName) = false) then buf.Append("SET first_name='").Append(newUser.FirstName).Append("'" ) |> ignore if (oldUser.LastName.Equals(newUser.LastName) = false) then buf.Append("SET last_name='").Append(newUser.LastName).Append("'" ) |> ignore if (oldUser.UserName.Equals(newUser.UserName) = false) then buf.Append("SET username='").Append(newUser.UserName).Append("'" ) |> ignore buf.Append(" WHERE id=").Append(newUser.Id).ToString() This doesn't properly put a , between any update parts after the first, for example: UPDATE users SET first_name='Firstname', last_name='lastname' WHERE id=... I could put in a mutable variable to keep track when the first part of the set clause is appended, but that seems wrong. I could just create an list of tuples, where each tuple is oldtext, newtext, columnname, so that I could then loop through the list and build up the query, but it seems that I should be passing in a StringBuilder to a recursive function, returning back a boolean which is then passed as a parameter to the recursive function. Does this seem to be the best approach, or is there a better one?

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  • http response to GET request - working in FF not Chromium

    - by Tyler
    For fun I'm trying to write a very simple server in C. When I send this response to Firefox it prints out the body "hello, world" but with Chromium it gives me a Error 100 (net::ERR_CONNECTION_CLOSED): Unknown error. This, I believe, is the relevant code: char *response = "HTTP/1.0 200 OK\r\nVary: Accept-Encoding, Accept-Language\r\nConnection: Close\r\nContent-Type: text/plain\r\nContent-Length:20\r\n\r\nhello, world"; if(send(new_fd, response, strlen(response), 0) == strlen(response)) { printf("sent\n"); }; close(new_fd); What am I missing? Thanks!

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  • Delete Drag and Drop Behavior of IKImageBrowserView

    - by PF1
    Hi Everyone: By default (it seems), IKImageBrowserView enables drag and drop to locations in the Finder. I would like to turn off this behavior but am unsure of how to do so. I was thinking that perhaps implementing the NSDraggingDestination protocol and overriding it could solve this, but so far it hasn't worked for me. Thanks for any help!

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  • Which languages are dynamically typed and compiled (and which are statically typed and interpreted)?

    - by Skilldrick
    In my reading on dynamic and static typing, I keep coming up against the assumption that statically typed languages are compiled, while dynamically typed languages are interpreted. I know that in general this is true, but I'm interested in the exceptions. I'd really like someone to not only give some examples of these exceptions, but try to explain why it was decided that these languages should work in this way.

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  • What is your favourite cleverly written functional code?

    - by sdcvvc
    What are your favourite short, mind-blowing snippets in functional languages? My two favourite ones are (Haskell): powerset = filterM (const [True, False]) foldl f v xs = foldr (\x g a -> g (f a x)) id xs v -- from Hutton's tutorial (I tagged the question as Haskell, but examples in all languages - including non-FP ones - are welcome as long as they are in functional spirit.)

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  • Getting "Illegal Seek" error after calling accept()

    - by Bilthon
    Well.. it's pretty much that, I seem to be getting a "Illegal Seek" error when checking my errno variable. The problem is that I have no idea of what that can mean. I know sockets are treated like files in unix, but I can't see how can this be related to sockets. What I'm doing exactly is: int sck = ::accept(m_socket, (struct sockaddr*)&client_address, (socklen_t*)&address_len); Then I get sck = -1 and errno = ESPIPE And the weird thing is that it happens randomly. I mean, sometimes the code works fine, and sometimes it just thows an exception. I'm working with threads so that's understandable. But I just would like to know what kind of behaviour makes the accept() call to set errno as ESPIPE so I could check the paramethers for instance. Thanks Nelson R. Pérez

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  • Linker library for OpenMP for Snow Leopard?

    - by unknownthreat
    Currently, I am trying out OpenMP on XCode 3.2.2 on Snow Leopard: #include <omp.h> #include <iostream> #include <stdio.h> int main (int argc, char * const argv[]) { #pragma omp parallel printf("Hello from thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads()); return 0; } I didn't include any linking libraries yet, so the linker complains: "_omp_get_thread_num", referenced from: _main in main.o "_omp_get_num_threads", referenced from: _main in main.o OK, fine, no problem, I take a look in the existing framework, looking for keywords such as openmp or omp... here comes the problem, where is the linking library? Or should I say, what is the name of the linking library for openMP? Is it dylib, framework or what? Or do I need to get it from somewhere first?

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  • What are all the disadvantages of using files as a means of communicating between two processes?

    - by Manny
    I have legacy code which I need to improve for performance reasons. My application comprises of two executables that need to exchange certain information. In the legacy code, one exe writes to a file ( the file name is passed as an argument to exe) and the second executable first checks if such a file exists; if does not exist checks again and when it finds it, then goes on to read the contents of the file. This way information in transferred between the two executables. The way the code is structured, the second executable is successful on the first try itself. Now I have to clean this code up and was wondering what are the disadvantages of using files as a means of communication rather than some inter-process communication like pipes.Is opening and reading a file more expensive than pipes? Are there any other disadvantages? And how significant do you think would be the performance degradation. The legacy code is run on both windows and linux.

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  • Make a function which returns the original list except the argument

    - by Alex
    I want make a function which takes a list of string and a string and returns NONE if there is no string in the string list, otherwise it returns SOME of the list of string which is the same as the original list of string except it doesn't contain the initial string (pattern): fun my_function (pattern, source_list) = case source_list of [] => NONE | [x] => if pattern = x then SOME [] else NONE | x::xs => if pattern = x then SOME (xs) else SOME (x) :: my_function (pattern, xs) (* this is wrong, what to do here?*) val a = my_function ("haha", ["12", "aaa", "bbb", "haha", "ccc", "ddd"]) (* should be SOME ["12", "aaa", "bbb", "ccc", "ddd"]*) val a2 = my_function ("haha2", ["123", "aaa", "bbb", "haha", "ccc"]) (*should be NONE*) val a3 = my_function ("haha3", ["haha3"]) (* should be SOME []*) I'm confused by the 3rd case: x::xs => .... What should do there? Note that I'd like not to use any sml library function.

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  • Do you have any tips for comments to keep them in step with the code? [closed]

    - by Rob Wells
    Possible Duplicate: How do you like your comments? G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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  • shell script passing subset of arguments

    - by arav
    From the wrapper shell scripts i am calling the Java program. I want the Unix shell script to pass all the arguments to java program except the EMAIL argument. HOW Can i remove the EMAIL argument and pass the rest of the arguments to the java program. EMAIL argument can come at any position. valArgs() { until [ $# -eq 0 ]; do case $1 in -EMAIL) MAILFLAG=Y shift break ;; esac done } main() { valArgs "$@" $JAVA_HOME/bin/java -d64 -jar WEB-INF/lib/test.jar "$@"

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  • How to acces File over the Network

    - by Polo
    Hi! I am having a hard time on this one, I have à folder over the network wit public accès (no credential restriction). I am trying to do à File.Exist or Directory.Exist and I keep on having a exception. Can somewone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\agoodip\Public") or File.exist(@"\agoodip\Public\test.txt") The exception I get is Path not found. Thanks!

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  • Wondering where to begin

    - by Cat
    Hello all. After being interested for years and years (and years), I have finally decided to start learning how to create software and web applications. Base on recommendations, I have started with learning the basics of web design first (which I am almost done with) and then will move on to the meat of my process: learning the languages. Problem is, I don't know where to start :/ PHP, Ruby, Perl...and where would SQL, JavaScript and .NET fit into the mix? I am assuming they build on each other/play off of each other somewhat so following some sort of 'order' will make the process more logical and digestible. You're probably thinking, "Just go to school for computer engineering, duh!" But I already have a degree and don't plan on going back to school. I believe I have an adequate aptitude for this sort of thing, and although it will be challenging, with the support of the community I know I can do it on my own. Thank in advance everyone and I am very sorry for the length. I look forward to hearing what all you have to say. Warm Regards, Cat

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  • C# Asynchronous Network IO and OutOfMemoryException

    - by The.Anti.9
    I'm working on a client/server application in C#, and I need to get Asynchronous sockets working so I can handle multiple connections at once. Technically it works the way it is now, but I get an OutOfMemoryException after about 3 minutes of running. MSDN says to use a WaitHandler to do WaitOne() after the socket.BeginAccept(), but it doesn't actually let me do that. When I try to do that in the code it says WaitHandler is an abstract class or interface, and I can't instantiate it. I thought maybe Id try a static reference, but it doesnt have teh WaitOne() method, just WaitAll() and WaitAny(). The main problem is that in the docs it doesn't give a full code snippet, so you can't actually see what their "wait handler" is coming from. its just a variable called allDone, which also has a Reset() method in the snippet, which a waithandler doesn't have. After digging around in their docs, I found some related thing about an AutoResetEvent in the Threading namespace. It has a WaitOne() and a Reset() method. So I tried that around the while(true) { ... socket.BeginAccept( ... ); ... }. Unfortunately this makes it only take one connection at a time. So I'm not really sure where to go. Here's my code: class ServerRunner { private Byte[] data = new Byte[2048]; private int size = 2048; private Socket server; static AutoResetEvent allDone = new AutoResetEvent(false); public ServerRunner() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, 33333); server.Bind(iep); Console.WriteLine("Server initialized.."); } public void Run() { server.Listen(100); Console.WriteLine("Listening..."); while (true) { //allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); //allDone.WaitOne(); } } void AcceptCon(IAsyncResult iar) { Socket oldserver = (Socket)iar.AsyncState; Socket client = oldserver.EndAccept(iar); Console.WriteLine(client.RemoteEndPoint.ToString() + " connected"); byte[] message = Encoding.ASCII.GetBytes("Welcome"); client.BeginSend(message, 0, message.Length, SocketFlags.None, new AsyncCallback(SendData), client); } void SendData(IAsyncResult iar) { Socket client = (Socket)iar.AsyncState; int sent = client.EndSend(iar); client.BeginReceive(data, 0, size, SocketFlags.None, new AsyncCallback(ReceiveData), client); } void ReceiveData(IAsyncResult iar) { Socket client = (Socket)iar.AsyncState; int recv = client.EndReceive(iar); if (recv == 0) { client.Close(); server.BeginAccept(new AsyncCallback(AcceptCon), server); return; } string receivedData = Encoding.ASCII.GetString(data, 0, recv); //process received data here byte[] message2 = Encoding.ASCII.GetBytes("reply"); client.BeginSend(message2, 0, message2.Length, SocketFlags.None, new AsyncCallback(SendData), client); } }

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  • How to detect internet connectivity using java program

    - by Sunil Kumar Sahoo
    How to write a java program which will tell me whether I have internet access or not. I donot want to ping or create connection with some external url because if that server will be down then my program will not work. I want reliable way to detect which will tell me 100% guarantee that whether I have internet connection or not irrespective of my Operating System. I want the program for the computers who are directly connected to internet. I have tried with the below program URL url = new URL("http://www.xyz.com/"); URLConnection conn = url.openConnection(); conn.connect(); I want something more appropriate than this program Thanks Sunil Kumar Sahoo

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  • From interpeted to native code: "dynamic" languages compiler support

    - by Daniel
    First, I am aware that dynamic languages is a term used mainly by a vendor; I am using it just to have a container word to include languages like Perl (a favorite of mine), Python, Tcl, Ruby, PHP and so on. They are interpreted but I am interested here to refer to languages featuring strong capability to support the programmer efficiency and the support for typical constructs of modern interpreted languages My question is: there are dynamic languages can be compiled efficiently in native executable code - typically for Windows platforms? Which ones? Maybe using some third part ad-hoc tools? I am not talking about huge executables carrying with them a full interpreter or some similar tricks nor some smart module able to include its own dependances or some required modules, but a honest, straight, standard, solid executable code. If not, there is some technical reason inhibiting the availability of such a best-of-both-world feature? Thanks! Daniel

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  • Find three numbers appeared only once

    - by shilk
    In a sequence of length n, where n=2k+3, that is there are k unique numbers appeared twice and three numbers appeared only once. The question is: how to find the three unique numbers that appeared only once? for example, in sequence 1 1 2 6 3 6 5 7 7 the three unique numbers are 2 3 5. Note: 3<=n<1e6 and the number will range from 1 to 2e9 Memory limits: 1000KB , this implies that we can't store the whole sequence. Method I have tried(Memory limit exceed): I initialize a tree, and when read in one number I try to remove it from the tree, if the remove returns false(not found), I add it to the tree. Finally, the tree has the three numbers. It works, but is Memory limit exceed. I know how to find one or two such number(s) using bit manipulation. So I wonder if we can find three using the same method(or some method similar)? Method to find one/two number(s) appeared only once: If there is one number appeared only once, we can apply XOR to the sequence to find it. If there are two, we can first apply XOR to the sequence, then separate the sequence into 2 parts by one bit of the result that is 1, and again apply XOR to the 2 parts, and we will find the answer.

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