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• Cancel UDP recvfrom in C on Unix

  - by hora

  I'm just starting to learn how network programming in C works, and I've written a small program that sends messages to and from a UNIX terminal. I'm using pthreads in my program, one of which essentially just waits on recvfrom() to receive a message. However, I want to be able to close all threads properly if the users chooses to quit the program. The way I have it set up right now, a different thread just cancels the thread waiting on recvfrom, but I'm worried this might not be a good idea since I'm leaving sockets unclosed and I'm not freeing all the memory I allocated. Is there a way to cancel a recvfrom() call, or some way to run a certain routine upon cancelling a pthread? Thanks.

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• How to create a container that holds different types of function pointers in C++?

  - by Alex

  I'm doing a linear genetic programming project, where programs are bred and evolved by means of natural evolution mechanisms. Their "DNA" is basically a container (I've used arrays and vectors successfully) which contain function pointers to a set of functions available. Now, for simple problems, such as mathematical problems, I could use one type-defined function pointer which could point to functions that all return a double and all take as parameters two doubles. Unfortunately this is not very practical. I need to be able to have a container which can have different sorts of function pointers, say a function pointer to a function which takes no arguments, or a function which takes one argument, or a function which returns something, etc (you get the idea)... Is there any way to do this using any kind of container ? Could I do that using a container which contains polymorphic classes, which in their turn have various kinds of function pointers? I hope someone can direct me towards a solution because redesigning everything I've done so far is going to be painful.

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• Efficient heaps in purely functional languages

  - by Kim

  As an exercise in Haskell, I'm trying to implement heapsort. The heap is usually implemented as an array in imperative languages, but this would be hugely inefficient in purely functional languages. So I've looked at binary heaps, but everything I found so far describes them from an imperative viewpoint and the algorithms presented are hard to translate to a functional setting. How to efficiently implement a heap in a purely functional language such as Haskell? Edit: By efficient I mean it should still be in O(n*log n), but it doesn't have to beat a C program. Also, I'd like to use purely functional programming. What else would be the point of doing it in Haskell?

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• What emoticons can you put into class names in your language?

  - by Chris Gill

  I've just had a "discussion" with a developer about naming classes in C#. My final throw away line was, "Let's not put any emoticons in our class names." I can't think of a way you could put emoticons in C# class names, but I haven't thought too hard about it. Is this possible? Does any programming language allow it? What would be the best/worst language to be able to perform this in? Update: The Scheme answer bests answers my question. It was a quick idea after a quick discussion so I'm going to accept after a short amount of time and then move on with my life. Thanks for the responses.

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• Open Source Contribution for a newbie programmer.

  - by sasayins

  Hi, I am teaching programming to my nephews and I want them to improve their skills by contributing to open source projects. Now my question is, do you know any open source project that suit for a newbie programmer. What I mean is, the project does not have a large codebase, the project is very interesting and the project is written in C because I chose C language as their starting language but you can suggest other project made in other language. My goal here are to improve their logic by reading other source codes, familiarize to the available development tools like bug tracker, version control system, etc. and open their interest in open source community. Thanks. =)

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• What would be the disadvantages/risks of using AF_UNSPEC?

  - by Kiril Kirov

  From Beej's Guide to Network programming You can force it to use IPv4 or IPv6 in the ai_family field, or leave it as AF_UNSPEC to use whatever. This is cool because your code can be IP version-agnostic. As the title says - what would be the disadvantages (or risks, if any) of always using AF_UNSPEC, instead of specifying IPv4 or IPv6? Or it's only for one reason - if the version is specified, this will guarantee that this and only this version is supported? A little background - I think about adding support for IPv6 in client-server (C++) applications and both versions should be supported. So I wondered if it's fine to use AF_UNSPEC or it's better to "recognize" the address from the string and use AF_INET6 or AF_INET, depending on the address.

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• Metatool for automatic xml code generation

  - by iceman

  I want to develop a programming tool for developers which can do automatic xml code generation for specifying a GUI design and its controls. The aim is to allow non-programmers specify GUI controls(which in this case perform higher level task unlike WinForms ) from a GUI. So the xml code generated is essentially an internal representation which programmers can understand and further use in any automatic GUI generator. So the workflow is GUI(non-programmers)-xml(for programmers)-GUI(non-programmers). Is there a Microsoft project similar to this?

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• Salary of a junior freelancer programmer

  - by Frank

  Hi, I'm pursuing my PhD in CS and starting freelancing to pay bills and get some experience. Since I'm new in the freelancing field, I was wondering how much you would charge for a junior programmer to do some work. Like many, I've started freelancing for website. I'm doing pretty much all the work (design, programming, finding hosting/domain). I would like to give details to my client in order for them to know how much cost every part involved in website development. How much should I charge? Charing a hourly rate or a price for the whole project? How you did it and why? Thanks

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• Setting up java configurations in eclipse. multiple .param files

  - by Charlie

  I'm going to be using ECJ for doing genetic programming and I haven't touched java in years. I'm working on setting up the eclipse environment and I'm catching a few snags. The ECJ source has several packages, and several sample programs come along with it. I ran one sample program (called tutorial1) by going to the run configurations and adding -file pathToParamsFile to the program arguments. This made it point to the params file of that tutorial and run that sample. In a new example I am testing (from the package gui) there are TWO params files. I tried pointing to just one param file and a program ran in the console, but there was supposed to be a GUI which did not load. I'm not sure what I'm doing wrong. Any help would be greaaatly appreciated.

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• facing outsourced wages, can i still eat and survive as a computing science major ?

  - by wefwgeweg

  offshore outsourced programmers charge fraction of what costs a North American developer. should I still pursue my major as computing science ? Why would companies spend more on North American/local developers where they can get the same quality if not better job done offshore ? I am just concerned for the development labor market, the free market wants the lowest cost provider. not just programming but many high skilled labor such as engineering, scientists, artists and etc. perhaps i should become a lawyer ?

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• Clojure: Testing every value from map operation for truth

  - by Ralph

  How can I test that every value in the collection returned by map is true? I am using the following: (defn test [f coll] (every? #(identity %) (map f coll))) with the anonymous function #(identity %), but I was wondering if there is a better way. I cannot use (apply and ...) because and is a macro. UPDATE: BTW, I am making my way through The Haskell Road to Logic, Maths, and Programming, by Kees Doets and Jan can Eijck, but doing the exercises in Clojure. It's a very interesting book.

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• How do I change careers to become a programmer with little 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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• How To Read Data using Ip Address

  - by DATT OZA

  I am doing punch card reader programming.. Establish connection with BioAccess V2 Device... socket successdully connected but data can't read... so how to read data ? Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream,ProtocolType.Tcp); var ipaddress = IPAddress.Parse("192.168.000.111"); IPAddress add = new IPAddress(ipaddress.GetAddressBytes()); EndPoint ep = new IPEndPoint(add, 5005); sock.Connect(ep); if(sock.connected) { } now what i have to do in IF BLOCK to read data ?

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• Vectorizing sums of different diagonals in a matrix

  - by reve_etrange

  I want to vectorize the following MATLAB code. I think it must be simple but I'm finding it confusing nevertheless. r = some constant less than m or n [m,n] = size(C); S = zeros(m-r,n-r); for i=1:m-r for j=1:n-r S(i,j) = sum(diag(C(i:i+r-1,j:j+r-1))); end end The code calculates a table of scores, S, for a dynamic programming algorithm, from another score table, C. The diagonal summing is to generate scores for individual pieces of the data used to generate C, for all possible pieces (of size r). Thanks in advance for any answers! Sorry if this one should be obvious...

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• Debugging F# code and functional style

  - by Roger Alsing

  I'm new to funcctional programming and have some questions regarding coding style and debugging. I'm under the impression that one should avoid storing results from funcction calls in a temp variable and then return that variable e.g. let someFunc foo = let result = match foo with | x -> ... | y -> ... result And instead do it like this (I might be way off?): let someFunc foo = match foo with | x -> ... | y -> ... Which works fine from a functionallity perspective, but it makes it way harder to debug. I have no way to examine the result if the right hand side of - does some funky stuff. So how should I deal with this kind of scenarios?

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• What division operator symbol would you pick?

  - by Mackenzie

  I am currently designing and implementing a small programming language as an extra-credit project in a class I'm taking. My problem is that the language has three numeric types: Long, Double, and Fraction. Fractions can be written in the language as proper or improper fractions (e.g. "2 1/3" or "1/2"). This fact leads to problems such as "2/3.5" (Long/Double) and "2/3"(Long/Long) not being handled correctly by the lexer.The best solution that I see is to change the division operator. So far, I think "\" is the best solution since "//" starts comments. Would you pick "\", if you were designing the language? Would you pick something else? If so, what? Note: changing the way fractions are written is not possible. Thanks in advance for your help,

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• Nested class with hidden constructor impossible in c#?

  - by luckyluke

  I' ve been doing some programming lately and faced an issue which i found weird in c#. (at least for me) public class Foo { //whatever public class FooSpecificCollection : List<Bar> { //implementation details } public FooSpecificCollection GetFoosStuff() { //return the collection } } I want the consumer of Foo to be able to obtain a reference to FooSpecificCollection, even perform some operations on it. Maybe even set it to some other property of Foo or smth like that, but not To be able to CREATE an instance of this class. (the only class that should be able to instatiate this collection should be Foo. Is my request really that far-fetched? I know that people way smarter defined c# but shouldn't there be such an option that a parent class can create a nested class instance but nobody else can't. So far I created a solution to make an abstract class, or interface available through the property and implement a concrete private class that is not available anywhere else. Is this a correct way to handle such a situation.?

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• Parsing a website

  - by Phenom

  I want to make a program that takes as user input a website address. The program then goes to that website, downloads it, and then parses the information inside. It outputs a new html file using the information from the website. Specifically, what this program will do is take certain links from the website, and put the links in the output html file, and it will discard everything else. Right now I just want to make it for websites that don't require a login, but later on I want to make it work for sites where you have to login, so it will have to be able to deal with cookies. I'll also want to later on have the program be able to explore certain links and download information from those other sites. What are the best programming languages or tools to do this?

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• C# how to create functions that are interpreted at runtime

  - by Lirik

  I'm making a Genetic Program, but I'm hitting a limitation with C# where I want to present new functions to the algorithm but I can't do it without recompiling the program. In essence I want the user of the program to provide the allowed functions and the GP will automatically use them. It would be great if the user is required to know as little about programming as possible. I want to plug in the new functions without compiling them into the program. In Python this is easy, since it's all interpreted, but I have no clue how to do it with C#. Does anybody know how to achieve this in C#? Are there any libraries, techniques, etc?

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• How to learn Haskell

  - by anderstornvig

  For a few days I've tried to wrap my head around the functional programming paradigm in Haskell. I've done this by reading tutorials and watching screencasts, but nothing really seems to stick. Now, in learning various imperative/OO languages (like C, Java, PHP), excercises have been a good way for me to go. But since I don't really know what Haskell is capable of and because there are many new concepts to utilize, I haven't known where to start. So, how did you learn Haskell? What made you really "break the ice"? Also, any good ideas for beginning excercises?

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• Why is the 'if' statement considered evil?

  - by Vadim

  I just came from Simple Design and Testing Conference. In one of the session we were talking about evil keywords in programming languages. Corey Haines, who proposed the subject, was convinced that if statement is absolute evil. His alternative was to create functions with predicates. Can you please explain to me why if is evil. I understand that you can write very ugly code abusing if. But I don't believe that it's that bad.

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• memristor is a new paradigm (fourth element in integrated circuits)? [closed]

  - by lsalamon

  The memristor will bring a new paradigm of programming, opened enormous opportunities to enable the machines to gain knowledge, creating a new paradigm toward the intelligence altificial. Do you believe that we are paving the way for the era of intelligent machines? More info about : Brain-like systems? "As for the human brain-like characteristics, memristor technology could one day lead to computer systems that can remember and associate patterns in a way similar to how people do. This could be used to substantially improve facial recognition technology or to provide more complex biometric recognition systems that could more effectively restrict access to personal information. These same pattern-matching capabilities could enable appliances that learn from experience and computers that can make decisions." [EDITED] The way is open. News on the subject Brain-Like Computer Closer to Realization

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• Learning how to program real things.

  - by Sean

  How would you guys recommend I actually learn to program real things? I mean, I know how to do basic academic things. I can implement a templated stack/queue/map/etc. data structure in C++ or Java or whatever. I can make a text-based hangman game or whatever. Etc etc. But how can I learn to program something real, something useful? I've done project Euler up to question 100 or so, and I feel like that's given me more mathematical maturity but not programming maturity. Should I buy a book and follow exercises, struggle through interesting projects, etc, ? In short, how did you guys transition from academic exercises to real, fun and/or useful programs?

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• Strange client's address returned throug accept(..) function.

  - by Negai

  Hi everyone, I'm a socket programming newbie. Here's a snippet: struct sockaddr_storage client_addr; ... client_addr_size = sizeof(client_addr); client_socket = accept( server_socket, (struct sockaddr *)&client_addr, &client_addr_size ); ... result = inet_ntop( AF_INET, &((struct sockaddr_in *)&client_addr)->sin_addr, client_addr_str, sizeof(client_addr_str) ); Whenever the client connects the address I get is 0.0.0.0 regardless from the host. Can anybody explain, what I'm doing wrong? Thanks.

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• What languages allow cross-platform native executables to be created?

  - by JT

  I'm frustrated to discover that Java lacks an acceptable solution for creating programs that will run via double-click. Other than .NET for Windows, what modern and high-level programming languages can I write code in that can be compiled for various platforms and run as a native/binary in each (Windows, Linux, OSX (optional)) Assuming I wanted to write code in python, for instance, is there a cohesive way that I could distribute my software which wouldn't require users to do anything special to get it to run? I want to write and distribute software for computer-illiterate and Java has turned out to be a real pain in this respect.

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