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  • C++ Program Flow: Sockets in an Object and the Main Function

    - by jfm429
    I have a rather tricky problem regarding C++ program flow using sockets. Basically what I have is this: a simple command-line socket server program that listens on a socket and accepts one connection at a time. When that connection is lost it opens up for further connections. That socket communication system is contained in a class. The class is fully capable of receiving the connections and mirroring the data received to the client. However, the class uses UNIX sockets, which are not object-oriented. My problem is that in my main() function, I have one line - the one that creates an instance of that object. The object then initializes and waits. But as soon as a connection is gained, the object's initialization function returns, and when that happens, the program quits. How do I somehow wait until this object is deleted before the program quits? Summary: main() creates instance of object Object listens Connection received Object's initialization function returns main() exits (!) What I want is for main() to somehow delay until that object is finished with what it's doing (aka it will delete itself) before it quits. Any thoughts?

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  • what is the programmatic parlance for this phenomenon?

    - by deostroll
    Here is javascript code (jquery) for adding a row of images: var tr = $('<tr>'); var td = '<td><img src="myimg.jpg"/></td>'; tr.append(td).append(td).append(td); $('#mytable tbody tr:eq(0)').before(tr); tr.empty(); //I really don't need this line... Technically tr.empty() shouldn't have worked. It actually does the opposite of what I want. What is the techinical term for this behaviour - You've added tr to the DOM, but any jquery function calls to that object still works, where as you'd normally not expect it to work i.e. make changes to the DOM?

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  • Function Composition in C++

    - by Channel72
    There are a lot of impressive Boost libraries such as Boost.Lambda or Boost.Phoenix which go a long way towards making C++ into a truly functional language. But is there a straightforward way to create a composite function from any 2 or more arbitrary functions or functors? If I have: int f(int x) and int g(int x), I want to do something like f . g which would statically generate a new function object equivalent to f(g(x)). This seems to be possible through various techniques, such as those discussed here. Certainly, you can chain calls to boost::lambda::bind to create a composite functor. But is there anything in Boost which easily allows you to take any 2 or more functions or function objects and combine them to create a single composite functor, similar to how you would do it in a language like Haskell?

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  • What alternative is there to writing a TCP/IP data relay?

    - by LoudNPossiblyRight
    I am about to write a tcp/ip data relay - application that passes a one way stream of data from one host/port to another host/port. Initially it will be generic, but later on i will customize it to the need of a specific business request. I am guessing that something generic already exists out there so my question is: Has anyone used a third party (preferably open source) data relay in a production environment, if so what is, and do you recommend it? Any platform is fine. Thanks.

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  • For distributed applications, which to use, ASIO vs. MPI?

    - by Rhubarb
    I am a bit confused about this. If you're building a distributed application, which in some cases may perform parallel operations (although not necessarily mathematical), should you use ASIO or something like MPI? I take it MPI is a higher level than ASIO, but it's not clear where in the stack one would begin.

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  • Problem with .release behavior in file_operations

    - by Yannick
    Hello, I'm dealing with a problem in a kernel module that get data from userspace using a /proc entry. I set open/write/release entries for my own defined /proc entry, and manage well to use it to get data from userspace. I handle errors in open/write functions well, and they are visible to user as open/fopen or write/fwrite/fprintf errors. But some of the errors can only be checked at close (because it's the time all the data is available). In these cases I return something different than 0, which I supposed to be in some way the value 'close' or 'fclose' will return to user. But whatever the value I return my close behave like if all is fine. To be sure I replaced all the release() code by a simple 'return(-1);' and wrote a program that open/write/close the /proc entry, and prints the close return value (and the errno). It always return '0' whatever the value I give. Behavior is the same with 'fclose', or by using shell mechanism (echo "..." /proc/my/entry). Any clue about this strange behavior that is not the one claimed in many tutorials I found? BTW I'm using RHEL5 kernel (2.6.18, redhat modified), on a 64bit system. Thanks. Regards, Yannick

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  • What is your company's stance on Developers using Laptops?

    - by codepunk
    I am a developer and my company is moving towards a "no laptop" policy in fear of them being lost or stolen and source code being compromised. Now I don't work for NASA, the military or anything labeled Top Secret but our code is very important to our business nonetheless (as all source code would be). I'll be honest, I disagree with this policy against laptops and wanted to see what others think. I'd like to know: What is your team/company's stance on laptops Your company's size and/or field (small, medium or large, Fortune 500, etc). Whether you've had to take any extra precautions (signing any additional legal, ensure your hard drive is encrypted, etc). Thanks!

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  • Sparse linear program solver

    - by Jacob
    This great SO answer points to a good sparse solver, but I've got constraints on x (for Ax = b) such that each element in x is >=0 an <=N. The first thing which comes to mind is an LP solver for large sparse matrices. Any ideas/recommendations?

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  • What is a good CPU/PC setup to speed up intensive C++/templates compilation?

    - by ApplePieIsGood
    I currently have a machine with an Opteron 275 (2.2Ghz), which is a dual core CPU, and 4GB of RAM, along with a very fast hard drive. I find that when compiling even somewhat simple projects that use C++ templates (think boost, etc.), my compile times can take quite a while (minutes for small things, much longer for bigger projects). Unfortunately only one of the cores is pegged at 100%, so I know it's not the I/O, and it would seem that there is no way to take advantage of the other core for C++ compilation?

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  • Misc. Naming: Can I place underscores instead of camel casing in modern languages?

    - by Bubba88
    Hi! I would like to ask some kind of permission (I hope that doesn't sound strange) from the people who have influence on the naming conventions in modern languages like F#, Scala, etc. My problem is - I just can't read camelCased code and wish I could write underscored_names at least in my internal implementations (not in API interface). This applies to just everything - local var names, method names, params.. (Not class names I think) It seems that now the camel-casing is preferred for example for the names of object methods, but could that be not the only way? What would you say; Can I go with underscored names in languages like I mentioned (F#, Scala)?

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  • Prolog: using the sort/2 predicate

    - by Øyvind Hauge
    So I'm trying to get rid of the wrapper clause by using the sort library predicate directly inside split. What split does is just generating a list of numbers from a list that looks like this: [1:2,3:2,4:6] ---split-- [1,2,3,2,4,6]. But the generated list contains duplicates, and I don't want that, so I'm using the wrapper to combine split and sort, which then generates the desired result: [1,2,3,4,6]. I'd really like to get rid of the wrapper and just use sort within split, however I keep getting "ERROR: sort/2: Arguments are not sufficiently instantiated." Any ideas? Thanks :) split([],[]). split([H1:H2|T],[H1,H2|NT]) :- split(T,NT). wrapper(L,Processed) :- split(L,L2), sort(L2,Processed).

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  • Template function as a template argument

    - by Kos
    I've just got confused how to implement something in a generic way in C++. It's a bit convoluted, so let me explain step by step. Consider such code: void a(int) { // do something } void b(int) { // something else } void function1() { a(123); a(456); } void function2() { b(123); b(456); } void test() { function1(); function2(); } It's easily noticable that function1 and function2 do the same, with the only different part being the internal function. Therefore, I want to make function generic to avoid code redundancy. I can do it using function pointers or templates. Let me choose the latter for now. My thinking is that it's better since the compiler will surely be able to inline the functions - am I correct? Can compilers still inline the calls if they are made via function pointers? This is a side-question. OK, back to the original point... A solution with templates: void a(int) { // do something } void b(int) { // something else } template<void (*param)(int) > void function() { param(123); param(456); } void test() { function<a>(); function<b>(); } All OK. But I'm running into a problem: Can I still do that if a and b are generics themselves? template<typename T> void a(T t) { // do something } template<typename T> void b(T t) { // something else } template< ...param... > // ??? void function() { param<SomeType>(someobj); param<AnotherType>(someotherobj); } void test() { function<a>(); function<b>(); } I know that a template parameter can be one of: a type, a template type, a value of a type. None of those seems to cover my situation. My main question is hence: How do I solve that, i.e. define function() in the last example? (Yes, function pointers seem to be a workaround in this exact case - provided they can also be inlined - but I'm looking for a general solution for this class of problems).

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  • UNIX script to parse Zone file (is this the best code?)

    - by Steve
    Hi, FOund the following on: http://mike.murraynet.net/2009/08/23/parsing-the-verisign-zone-file-with-os-x/ Can unix-masters have a look at it and see if its the best possible way to gather the unique domainsnames in a zone file? For .NET domains: grep “^[a-zA-Z0-9-]+ NS .” net.zone|sed “s/NS .//”|uniq netdomains.txt For .COM domains: grep “^[a-zA-Z0-9-]+ NS .” com.zone|sed “s/NS .//”|uniq comdomains.txt For .EDU domains: grep “^[a-zA-Z0-9-]+ NS .” edu.zone|sed “s/NS .//”|uniq edudomains.txt

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  • What is the fastest way to do division in C for 8bit MCUs?

    - by Jordan S
    I am working on the firmware for a device that uses an 8bit mcu (8051 architecture). I am using SDCC (Small Device C Compiler). I have a function that I use to set the speed of a stepper motor that my circuit is driving. The speed is set by loading a desired value into the reload register for a timer. I have a variable, MotorSpeed that is in the range of 0 to 1200 which represents pulses per second to the motor. My function to convert MotorSpeed to the correct 16bit reload value is shown below. I know that float point operations are pretty slow and I am wondering if there is a faster way of doing this... void SetSpeed() { float t = MotorSpeed; unsigned int j = 0; t = 1/t ; t = t / 0.000001; j = MaxInt - t; TMR3RL = j; // Set reload register for desired freq return; }

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  • socket timeout and remove O_NONBLOCK option

    - by juxstapose
    Hello, I implemented a socket timeout and retry but in order to do it I had to set the socket as a non-blocking socket. However, I need the socket to block. This was my attempt at a solution to these two problems. This is not working. Subsequent send calls block but never send any data. When I connect without the select and the timeout, subsequent send calls work normally. References: C: socket connection timeout How to reset a socket back to blocking mode (after I set it to nonblocking mode)? Code: fd_set fdset; struct timeval tv; fcntl(dsock, F_SETFL, O_NONBLOCK); tv.tv_sec = theDeviceTimeout; tv.tv_usec = 0; int retries=0; logi(theLogOutput, LOG_INFO, "connecting to device socket num retrys: %i", theDeviceRetry); for(retries=0;retries<theDeviceRetry;retries++) { connect(dsock, (struct sockaddr *)&daddr, sizeof daddr); FD_ZERO(&fdset); FD_SET(dsock, &fdset); if (select(dsock + 1, NULL, &fdset, NULL, &tv) == 1) { int so_error; socklen_t slen = sizeof so_error; getsockopt(dsock, SOL_SOCKET, SO_ERROR, &so_error, &slen); if (so_error == 0) { logi(theLogOutput, LOG_INFO, "connected to socket on port %i on %s", theDevicePort, theDeviceIP); break; } else { logi(theLogOutput, LOG_WARN, "connect to %i failed on ip %s because %s retries %i", theDevicePort, theDeviceIP, strerror(errno), retries); logi(theLogOutput, LOG_WARN, "failed to connect to device %s", strerror(errno)); logi(theLogOutput, LOG_WARN, "error: %i %s", so_error, strerror(so_error)); continue; } } } int opts; opts = fcntl(dsock,F_GETFL); logi(theLogOutput, LOG_DEBUG, "clearing nonblock option %i retries %i", opts, retries); opts ^= O_NONBLOCK; fcntl(dsock, F_SETFL, opts);

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  • MySQL: Get only count of result set.

    - by Varun
    I am using MVC with PHP/MySQL. Suppose I am using 10 functions with different queries for fetching details from the database. But at other times I may want to get only the count of the result that will be returned by the query. What is the standard way to handle such situation. Should I write 10 more functions which duplicate almost whole query and return only the count. Or Should I always return the count also with the result set Or I can pass a flag to indicate that the function should return count only, and then based on the flag I will dynamically generate the (select part of) query. Or Is there a better way?

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  • what to do with a flawed C++ skills test

    - by Mike Landis
    In the following gcc.gnu.org post, Nathan Myers says that a C++ skills test at SANS Consulting Services contained three errors in nine questions: Looking around, one of fthe first on-line C++ skills tests I ran across was: http://www.geekinterview.com/question_details/13090 I looked at question 1... find(int x,int y) { return ((x<y)?0:(x-y)):} call find(a,find(a,b)) use to find (a) maximum of a,b (b) minimum of a,b (c) positive difference of a,b (d) sum of a,b ... immediately wondering why would anyone write anything so obtuse. Getting past the absurdity, I didn't really like any of the answers, immediately eliminating (a) and (b) because you can get back zero (which is neither a nor b) in a variety of circumstances. Sum or difference seemed more likely, except that you could also get zero regardless of the magnitudes of a and b. So... I put Matlab to work (code below) and found: when either a or b is negative you get zero; when b a you get a; otherwise you get b, so the answer is (b) min(a,b), if a and b are positive, though strictly speaking the answer should be none of the above because there are no range restrictions on either variable. That forces test takers into a dilemma - choose the best available answer and be wrong in 3 of 4 quadrants, or don't answer, leaving the door open to the conclusion that the grader thinks you couldn't figure it out. The solution for test givers is to fix the test, but in the interim, what's the right course of action for test takers? Complain about the questions? function z = findfunc(x,y) for i=1:length(x) if x(i) < y(i) z(i) = 0; else z(i) = x(i) - y(i); end end end function [b,d1,z] = plotstuff() k = 50; a = [-k:1:k]; b = (2*k+1) * rand(length(a),1) - k; d1 = findfunc(a,b); z = findfunc(a,d1); plot( a, b, 'r.', a, d1, 'g-', a, z, 'b-'); end

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  • scheme2lisp::define function and pass it as parameter

    - by Stas
    Hi! Im need translate some code from scheme to common lisp. Now I have something like this (defun sum (term a next b) (if (> a b) 0 (+ (term a) (sum term (next a) b)))) (defun sum-int (a b) (defun (ident x) x ) (sum ident a 1+ b)) But it doesn't interprete with out errors. * - DEFUN: the name of a function must be a symbol, not (IDENT X) Help me plese. Thanks

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  • read angles in radian and convert them in degrees/minutes/seconds

    - by Amadou
    n=0; disp('This program performs an angle conversion'); disp('input data set to a straight line. Enter the name'); disp('of the file containing the input Lambda in radian: '); filename = input(' ','s'); [fid,msg] = fopen(filename,'rt'); if fid < 0 disp(msg); else A=textscan(fid, '%g',1); while ~feof(fid) Lambda = A(1); n = n + 1; A = textscan(fid, '%f',1); end fclose(fid); end Alpha=Lambda*180/pi; fprintf('Angle converted from radian to degree/minutes/seconds:\n'); fprintf('Alpha =%12d\n',Alpha); fprintf('No of angles =%12d\n',n);

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