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• Which frameworks (and associated languages) support class replacement?

  - by Alix

  Hi, I'm writing my master thesis, which deals with AOP in .NET, among other things, and I mention the lack of support for replacing classes at load time as an important factor in the fact that there are currently no .NET AOP frameworks that perform true dynamic weaving -- not without imposing the requirement that woven classes must extend ContextBoundObject or MarshalByRefObject or expose all their semantics on an interface. You can however do this with the JVM thanks to ClassFileTransformer: You extend ClassFileTransformer. You subscribe to the class load event. On class load, you rewrite the class and replace it. All this is very well, but my project director has asked me, quite in the last minute, to give him a list of frameworks (and associated languages) that do / do not support class replacement. I really have no time to look for this now: I wouldn't feel comfortable just doing a superficial research and potentially putting erroneous information in my thesis. So I ask you, oh almighty programming community, can you help out? Of course, I'm not asking you to research this yourselves. Simply, if you know for sure that a particular framework supports / doesn't support this, leave it as an answer. If you're not sure please don't forget to point it out. Thanks so much!

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• Which languages support class replacement?

  - by Alix

  Hi, I'm writing my master thesis, which deals with AOP in .NET, among other things, and I mention the lack of support for replacing classes at load time as an important factor in the fact that there are currently no .NET AOP frameworks that perform true dynamic weaving -- not without imposing the requirement that woven classes must extend ContextBoundObject or MarshalByRefObject or expose all their semantics on an interface. You can however do this in Java thanks to ClassFileTransformer: You extend ClassFileTransformer. You subscribe to the class load event. On class load, you rewrite the class and replace it. All this is very well, but my project director has asked me, quite in the last minute, to give him a list of languages that do / do not support class replacement. I really have no time to look for this now: I wouldn't feel comfortable just doing a superficial research and potentially putting erroneous information in my thesis. So I ask you, oh almighty programming community, can you help out? Of course, I'm not asking you to research this yourselves. Simply, if you know for sure that a particular language supports / doesn't support this, leave it as an answer. If you're not sure please don't forget to point it out. Thanks so much!

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• computes the number of possible orderings of n objects under the relations < and =

  - by hilal

  Here is the problem : Give a algorithm that takes a positive integer n as input, and computes the number of possible orderings of n objects under the relations < and =. For example, if n = 3 the 13 possible orderings are as follows: a = b = c, a = b < c, a < b = c, a < b < c, a < c < b, a = c < b, b < a = c, b < a < c, b < c < a, b = c < a, c < a = b, c < a < b, c < b < a. Your algorithm should run in time polynomial in n. I'm null to this problem. Can you find any solution to this dynamic-programming problem?

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• sendto: Network unreachable

  - by devin

  Hello. I have two machines I'm testing my code on, one works fine, the other I'm having some problems and I don't know why it is. I'm using an object (C++) for the networking part of my project. On the server side, I do this: (error checking removed for clarity) res = getaddrinfo(NULL, port, &hints, &server)) < 0 for(p=server; p!=NULL; p=p->ai_next){ fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol); if(fd<0){ continue; } if(bind(fd, p->ai_addr, p->ai_addrlen)<0){ close(fd); continue; } break; } This all works. I then make an object with this constructor net::net(int fd, struct sockaddr *other, socklen_t *other_len){ int counter; this->fd = fd; if(other != NULL){ this->other.sa_family = other->sa_family; for(counter=0;counter<13;counter++) this->other.sa_data[counter]=other->sa_data[counter]; } else cerr << "Networking error" << endl; this->other_len = *other_len; } void net::gsend(string s){ if(sendto(this->fd, s.c_str(), s.size()+1, 0, &(this->other), this->other_len)<0){ cerr << "Error Sending, " << s << endl; cerr << strerror(errno) << endl; } return; } string net::grecv(){ stringstream ss; string s; char buf[BUFSIZE]; buf[BUFSIZE-1] = '\0'; if(recvfrom(this->fd, buf, BUFSIZE-1, 0, &(this->other), &(this->other_len))<0){ cerr << "Error Recieving\n"; cerr << strerror(errno) << endl; } // convert to c++ string and if there are multiple trailing ';' remove them ss << buf; s=ss.str(); while(s.find(";;", s.size()-2) != string::npos) s.erase(s.size()-1,1); return s; } So my problem is, is that on one machine, everything works fine. On another, everything works fine until I call my server's gsend() function. In which I get a "Error: Network Unreachable." I call gercv() first before calling gsend() too. Can anyone help me? I would really appreciate it.

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• How do you use stl's functions like for_each?

  - by thomas-gies

  I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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• Ruby: counters, counting and incrementing

  - by Shyam

  Hi, If you have seen my previous questions, you'd already know I am a big nuby when it comes to Ruby. So, I discovered this website which is intended for C programming, but I thought whatever one can do in C, must be possible in Ruby (and more readable too). The challenge is to print out a bunch of numbers. I discovered this nifty method .upto() and I used a block (and actually understanding its purpose). However, in IRb, I got some unexpected behavior. class MyCounter def run 1.upto(10) { |x| print x.to_s + " " } end end irb(main):033:0> q = MyCounter.new => #<MyCounter:0x5dca0> irb(main):034:0> q.run 1 2 3 4 5 6 7 8 9 10 => 1 I have no idea where the = 1 comes from :S Should I do this otherwise? I am expecting to have this result: 1 2 3 4 5 6 7 8 9 10 Thank you for your answers, comments and feedback!

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• Is it OK to write code after [super dealloc]? (Objective-C)

  - by Richard J. Ross III

  I have a situation in my code, where I cannot clean up my classes objects without first calling [super dealloc]. It is something like this: // Baseclass.m @implmentation Baseclass ... -(void) dealloc { [self _removeAllData]; [aVariableThatBelongsToMe release]; [anotherVariableThatBelongsToMe release]; [super dealloc]; } ... @end This works great. My problem is, when I went to subclass this huge and nasty class (over 2000 lines of gross code), I ran into a problem: when I released my objects before calling [super dealloc] I had zombies running through the code that were activated when I called the [self _removeAllData] method. // Subclass.m @implementation Subclass ... -(void) deallloc { [super dealloc]; [someObjectUsedInTheRemoveAllDataMethod release]; } ... @end This works great, and It didn't require me to refactor any code. My question Is this: Is it safe for me to do this, or should I refactor my code? Or maybe autorelease the objects? I am programming for iPhone if that matters any.

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• Freelance web hosting - what are good LAMP choices?

  - by tkotitan

  I think it's best if I ask this question with an example scenario. Let's say your mom-and-pop local hardware store has never had a website, and they want you, the freelance developer to build them a website. You have all the skills to run a LAMP setup and admin a system, so the difficult question you ask yourself is - where will I host it? As you aren't going to host it out of the machine in your apartment. Let's say you want to be able to customize your own system, install the version of PHP you want, and manage your own database. Perhaps the best kind of hosting is to get a virtual machine so you can customize the system as you see fit. But this essentially a "set it and forget it" site you make, bill by the hour for, and then are done. In other words, the hosting should not be an issue. Given the requirements of hosting a website: Unlimited growth potential needing good amounts of bandwidth to handle visitors Wide range of system and programming options allowing it to be portable Relatively cheap (not necessarily the cheapest) or reasonable scaling cost Reliable hosting with good support Hosted entirely on the host company's hardware Who would you pick to host this website? Yes I am asking for a business/company recommendation. Is there a clear answer for this scenario, or a good source that can reliably give the current answer? I know there are all kinds of schemes out there. I'm just wondering if any one company fills the bill for freelancers and stands out in such a crowded market.

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• Help! I'm a Haskell Newbie

  - by Darknight

  I've only just dipped my toe in the world of Haskell as part of my journey of programming enlightenment (moving on from, procedural to OOP to concurrent to now functional). I've been trying an online Haskell Evaluator. However I'm now stuck on a problem: Create a simple function that gives the total sum of an array of numbers. In a procedural language this for me is easy enough (using recursion) (c#) : private int sum(ArrayList x, int i) { if (!(x.Count < i + 1)) { int t = 0; t = x.Item(i); t = sum(x, i + 1) + t; return t; } } All very fine however my failed attempt at Haskell was thus: let sum x = x+sum in map sum [1..10] this resulted in the following error (from that above mentioned website): Occurs check: cannot construct the infinite type: a = a -> t Please bear in mind I've only used Haskell for the last 30 minutes! I'm not looking simply for an answer but a more explanation of it. Thanks in advanced.

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• Alter a function as a parameter before evaluating it in R?

  - by Shane

  Is there any way, given a function passed as a parameter, to alter its input parameter string before evaluating it? Here's pseudo-code for what I'm hoping to achieve: test.func <- function(a, b) { # here I want to alter the b expression before evaluating it: b(..., val1=a) } Given the function call passed to b, I want to add in a as another parameter without needing to always specify ... in the b call. So the output from this test.func call should be: test.func(a="a", b=paste(1, 2)) "1" "2" "a" Edit: Another way I could see doing something like this would be if I could assign the additional parameter within the scope of the parent function (again, as pseudo-code); in this case a would be within the scope of t1 and hence t2, but not globally assigned: t2 <- function(...) { paste(a=a, ...) } t1 <- function(a, b) { local( { a <<- a; b } ) } t1(a="a", b=t2(1, 2)) This is somewhat akin to currying in that I'm nesting the parameter within the function itself. Edit 2: Just to add one more comment to this: I realize that one related approach could be to use "prototype-based programming" such that things would be inherited (which could be achieved with the proto package). But I was hoping for a easier way to simply alter the input parameters before evaluating in R.

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• Parallelize or vectorize all-against-all operation on a large number of matrices?

  - by reve_etrange

  I have approximately 5,000 matrices with the same number of rows and varying numbers of columns (20 x ~200). Each of these matrices must be compared against every other in a dynamic programming algorithm. In this question, I asked how to perform the comparison quickly and was given an excellent answer involving a 2D convolution. Serially, iteratively applying that method, like so list = who('data_matrix_prefix*') H = cell(numel(list),numel(list)); for i=1:numel(list) for j=1:numel(list) if i ~= j eval([ 'H{i,j} = compare(' char(list(i)) ',' char(list(j)) ');']); end end end is fast for small subsets of the data (e.g. for 9 matrices, 9*9 - 9 = 72 calls are made in ~1 s). However, operating on all the data requires almost 25 million calls. I have also tried using deal() to make a cell array composed entirely of the next element in data, so I could use cellfun() in a single loop: # who(), load() and struct2cell() calls place k data matrices in a 1D cell array called data. nextData = cell(k,1); for i=1:k [nextData{:}] = deal(data{i}); H{:,i} = cellfun(@compare,data,nextData,'UniformOutput',false); end Unfortunately, this is not really any faster, because all the time is in compare(). Both of these code examples seem ill-suited for parallelization. I'm having trouble figuring out how to make my variables sliced. compare() is totally vectorized; it uses matrix multiplication and conv2() exclusively (I am under the impression that all of these operations, including the cellfun(), should be multithreaded in MATLAB?). Does anyone see a (explicitly) parallelized solution or better vectorization of the problem?

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• Finding k elements of length-n list that sum to less than t in O(nlogk) time

  - by tresbot

  This is from Programming Pearls ed. 2, Column 2, Problem 8: Given a set of n real numbers, a real number t, and an integer k, how quickly can you determine whether there exists a k-element subset of the set that sums to at most t? One easy solution is to sort and sum the first k elements, which is our best hope to find such a sum. However, in the solutions section Bentley alludes to a solution that takes nlog(k) time, though he gives no hints for how to find it. I've been struggling with this; one thought I had was to go through the list and add all the elements less than t/k (in O(n) time); say there are m1 < k such elements, and they sum to s1 < t. Then we are left needing k - m1 elements, so we can scan through the list again in O(n) time looking for all elements less than (t - s1)/(k - m1). Add in again, to get s2 and m2, then again if m2 < k, look for all elements less than (t - s2)/(k - m2). So: def kSubsetSumUnderT(inList, k, t): outList = [] s = 0 m = 0 while len(outList) < k: toJoin = [i for i in inList where i < (t - s)/(k - m)] if len(toJoin): if len(toJoin) >= k - m: toJoin.sort() if(s0 + sum(toJoin[0:(k - m - 1)]) < t: return True return False outList = outList + toJoin s += sum(toJoin) m += len(toJoin) else: return False My intuition is that this might be the O(nlog(k)) algorithm, but I am having a hard time proving it to myself. Thoughts?

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• Curl_errno=55, "Failed sending network data."

  - by 4dplane

  Hi all: I have a php script that updates a database via an api. This script works on one server but not on another. Both servers have curl enabled and they have php 5.2.6 or above. The error happens in the do_put() method. The rest of the script seems to be fine. I have found that: curl_errno= 55 = "Failed sending network data". curl_error= select/poll returned error <?php //phpinfo(); require_once "class.DelveAuthUtil.php"; $access_key = ""; $secret = "W"; $org_id = ""; $media_id = ""; $new_tag_name = "uvideo"; $assign_tag_to_media_url = "http://api..com/rest/organizations/$org_id/media/$media_id/properties/tags/$new_tag_name"; $signed_create_new_tag_url = DAU::authenticate_request("PUT", $assign_tag_to_media_url, $access_key, $secret); # perform the creation of the new custom property $put_response = do_put($signed_create_new_tag_url); # Execute the POST function do_post($url, $params=array()) { # Combine parameters $param_string = ""; foreach ($params as $key => $value) { $value = urlencode($value); $param_string = $param_string . "&$key=$value"; } // Get the curl session object $session = curl_init($url); // Set the POST options. curl_setopt ($session, CURLOPT_POST, true); curl_setopt ($session, CURLOPT_POSTFIELDS, $param_string); curl_setopt($session, CURLOPT_HEADER, false); curl_setopt($session, CURLOPT_RETURNTRANSFER, true); // Do the POST and then close the session $response = curl_exec($session); curl_close($session); return $response; } # Execute the PUT function do_put($url) { // Get the curl session object $session = curl_init($url); print(" <br> session= " . $session . "<br>"); // Set the PUT options. print ("opt0= " . curl_setopt($session, CURLOPT_VERBOSE, TRUE) . "<br>"); print ("opt1= " . curl_setopt ($session, CURLOPT_PUT, true) . "<br>"); print ("opt2= " . curl_setopt ($session, CURLOPT_HEADER, false) . "<br>"); print ("opt3= " . curl_setopt ($session, CURLOPT_RETURNTRANSFER, true) . "<br>"); // Do the PUT and then close the session $response = curl_exec($session); if (curl_errno($session)) { print ( "curl_errno= " . curl_errno($session). "<br>"); print( "curl_error= " . curl_error($session) . "<br>"); } else { curl_close($session); } } I have small lead in the Apache log - there is an SSL issue that I do not know how to resolve. [Thu Mar 25 15:57:58 2010] [warn] Init: You should not use name-based virtual hosts in conjunction with SSL!! [Thu Mar 25 15:57:58 2010] [notice] Apache/2.2.3 (CentOS) configured -- resuming normal operations [Thu Mar 25 15:58:59 2010] [notice] caught SIGTERM, shutting down [Thu Mar 25 15:58:59 2010] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Thu Mar 25 15:58:59 2010] [warn] RSA server certificate is a CA certificate (BasicConstraints: CA == TRUE !?) [Thu Mar 25 15:58:59 2010] [warn] RSA server certificate CommonName (CN) `yourvps.a2hosting.com' does NOT match server name!? [Thu Mar 25 15:58:59 2010] [warn] RSA server certificate is a CA certificate (BasicConstraints: CA == TRUE !?) [Thu Mar 25 15:58:59 2010] [warn] RSA server certificate CommonName (CN) `yourvps.a2hosting.com' does NOT match server name!? [Thu Mar 25 15:58:59 2010] [warn] Init: SSL server IP/port conflict: my1.com:443 (/home/httpd/my.com/conf/kloxo.my1.com:69) vs. elggtest.my1.com:443 (/home/httpd/elggtest.my1.com/conf/kloxo.elggtest.my1.com:71) [Thu Mar 25 15:58:59 2010] [warn] Init: You should not use name-based virtual hosts in conjunction with SSL!! [Thu Mar 25 15:58:59 2010] [notice] Digest: generating secret for digest authentication ... [Thu Mar 25 15:58:59 2010] [notice] Digest: done [Thu Mar 25 15:59:00 2010] [warn] RSA server certificate is a CA certificate (BasicConstraints: CA == TRUE !?) [Thu Mar 25 15:59:00 2010] [warn] RSA server certificate CommonName (CN) `yourvps.a2hosting.com' does NOT match server name!? [Thu Mar 25 15:59:00 2010] [warn] RSA server certificate is a CA certificate (BasicConstraints: CA == TRUE !?) [Thu Mar 25 15:59:00 2010] [warn] RSA server certificate CommonName (CN) `yourvps.a2hosting.com' does NOT match server name!? [Thu Mar 25 15:59:00 2010] [warn] Init: SSL server IP/port conflict: my1.com:443 (/home/httpd/my1.com/conf/kloxo.my1.com:69) vs. elggtest.my1.com:443 (/home/httpd/elggtest.my1.com/conf/kloxo.elggtest.my1.com:71) [Thu Mar 25 15:59:00 2010] [warn] Init: You should not use name-based virtual hosts in conjunction with SSL!! [Thu Mar 25 15:59:00 2010] [notice] Apache/2.2.3 (CentOS) configured -- resuming normal operations[/PHP] Any help would be great! Thanks, 4dplane

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• Autoloading Development or Production configs (best practices)

  - by Xeoncross

  When programming sites you usually have one set of config files for the development environment and another set for the production server (or one file with both settings). I am assuming all projects should be handled by version control like git or svn. Manual file transfers (like FTP) is wrong on so many levels. How you enable/disable the correct settings (so that your system knows which ones to use) is a problem for me. Each system I work on just kind of jimmy-rigs a solution. Below are the 3 methods I know of and I am hoping that someone can submit a more elegant solutions. 1) File Based The system loads a folder structure based on the URL requested. /site.com /site.fakeTLD /lib index.php For example, if the url is http://site.com then the system loads the production config files located in the site.com folder. However, if I'm working on the site locally I visit http://site.fakeTLD to work on the local copy of the site. To setup this I edit my hosts file and add site.fakeTLD to point to my own computer (127.0.0.1/localhost) and then create a vhost in apache. So now I can work on the codebase locally and then push to the server without any trouble. The problem is that this is susceptible to a "host" injection attack. So someone loading site.com could set the host to site.fakeTLD and then the system would load my development config files instead of production. 2) Config Based The config files contain on section for development - and one for production. The problem is that each time you go to push your changes to the repo you have to edit the file to specify which set of config options should be used. $use = 'production'; //'development'; This leaves the repo open to human error should one of the developers forget to enable the right setting. 3) File System Check Based All the development machines have an extra empty file called "development.txt" or something. Each time the system loads it checks for this file - if found then it knows it is in development mode - if missing then it knows it is in production mode. Since the file is NEVER ADDED to the repo then it will never be pushed (and checked out) on the production machine. However, this just doesn't feel right and causes a slight slow down since all filesystem checks are slow. Is there anyway that the server can auto-detect wither to use the development or production configs?

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• Receiving broadcast messages

  - by Prasad

  Hi, I'm trying to receive broadcast messages using C# code in an ISDN network with BRI interface at my end. I see the packets sent to the broadcast ip address (239.255.255.255) on some ports using Comm View tool. But when I try to listen to this IP address, it says the address is not in a valid context. But when I send broadcast messages to 255.255.255.255 on a port, I can receive those messages with the below code.. What could be the problem with this ip address - 239.255.255.255 ? The code I use to listen to broadcast messages is.. UdpClient udp = new UdpClient(); IPEndPoint receiveEndPoint = new IPEndPoint(IPAddress.Any, 8013); // If I use IPAddress.Parse("239.255.255.255") to listen to, // it says "the address is not in a valid // context." udp.Client.Bind(receiveEndPoint); udp.BeginReceive(_Callback, udp); static private void _Callback(IAsyncResult iar) { try { UdpClient client = (UdpClient)iar.AsyncState; client.BeginReceive(_Callback, client); IPEndPoint ipRemote = new IPEndPoint(IPAddress.Any, 8013); byte[] rgb = client.EndReceive(iar, ref ipRemote); Console.WriteLine("Received {0} bytes: \"{1}\"", rgb.Length.ToString(), Encoding.UTF8.GetString(rgb)); } catch (ObjectDisposedException) { Console.WriteLine("closing listening socket"); } catch (Exception exc) { Console.WriteLine("Listening socket error: \"" + exc.Message + "\""); } } There are packets sent to the broadcast ipaddress (239.255.255.255) which I can see in Commview tool, but can't receive them from the code... Can anybody help me out please? Thanking you in advance, Prasad Kancharla.

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• What are five things you hate about your favorite language?

  - by brian d foy

  There's been a cluster of Perl-hate on Stackoverflow lately, so I thought I'd bring my "Five things you hate about your favorite language" question to StackOverflow. Take your favorite language and tell me five things you hate about it. Those might be things that just annoy you, admitted design flaws, recognized performance problems, or any other category. You just have to hate it, and it has to be your favorite language. Don't compare it to another language, and don't talk about languages that you already hate. Don't talk about the things you like in your favorite language. I just want to hear the things that you hate but tolerate so you can use all of the other stuff, and I want to hear it about the language you wished other people would use. I ask this whenever someone tries to push their favorite language on me, and sometimes as an interview question. If someone can't find five things to hate about his favorite tool, he don't know it well enough to either advocate it or pull in the big dollars using it. He hasn't used it in enough different situations to fully explore it. He's advocating it as a culture or religion, which means that if I don't choose his favorite technology, I'm wrong. I don't care that much which language you use. Don't want to use a particular language? Then don't. You go through due diligence to make an informed choice and still don't use it? Fine. Sometimes the right answer is "You have a strong programming team with good practices and a lot of experience in Bar. Changing to Foo would be stupid." This is a good question for code reviews too. People who really know a codebase will have all sorts of suggestions for it, and those who don't know it so well have non-specific complaints. I ask things like "If you could start over on this project, what would you do differently?" In this fantasy land, users and programmers get to complain about anything and everything they don't like. "I want a better interface", "I want to separate the model from the view", "I'd use this module instead of this other one", "I'd rename this set of methods", or whatever they really don't like about the current situation. That's how I get a handle on how much a particular developer knows about the codebase. It's also a clue about how much of the programmer's ego is tied up in what he's telling me. Hate isn't the only dimension of figuring out how much people know, but I've found it to be a pretty good one. The things that they hate also give me a clue how well they are thinking about the subject.

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• Cross-Platform Language + GUI Toolkit for Prototyping Multimedia Applications

  - by msutherl

  I'm looking for a language + GUI toolkit for rapidly prototyping utility applications for multimedia installations. I've been working with Max/MSP/Jitter for many years, but I'd like to add a text-based language to my 'arsenal' for tasks apart from 'content production'. (When it comes to actual media synthesis, my choices are clear [SuperCollider + MSP for audio, Jitter + Quartz + openFrameworks for video]). I'm looking for something that maintains some of the advantages of Max, but is lower-level, faster, more cross-platfrom (Linux support), and text-based. Integration with powerful sound/video libraries is not a requirement. Some requirements: Cross-platform (at least OSX and Linux, Windows is a plus) Fast and easy cross-platform GUIs with no platform-specific modification GUI code separated from backend code as much as possible Good for interfacing with external serial devices (micro-controllers) Good network support (UDP/TCP) Good libraries for multi-media (video, sound, OSC) are a plus Asynchronous synchronous UNIX integration is a plus The options that come to mind: AS3/Flex (not a fan of AS3 or the idea of running in the Flash Player) openFrameworks (C++ framework, perhaps a bit too low level [looking for fast development time] and biased toward video work) Java w/ Processing libraries (like openFrameworks, just slower) Python + Qt (is Qt appropriate for rapid prototyping?) Python + Another GUI toolkit SuperCollider + Swing (yucky GUI development) Java w/ SWT Any other options? What do you recommend?

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• Design Technique: How to design a complex system for processing orders, products and units.

  - by Shyam

  Hi, Programming is fun: I learned that by trying out simple challenges, reading up some books and following some tutorials. I am able to grasp the concepts of writing with OO (I do so in Ruby), and write a bit of code myself. What bugs me though is that I feel re-inventing the wheel: I haven't followed an education or found a book (a free one that is) that explains me the why's instead of the how's, and I've learned from the A-team that it is the plan that makes it come together. So, armed with my nuby Ruby skills, I decided I wanted to program a virtual store. I figured out the following: My virtual Store will have: Products and Services Inventories Orders and Shipping Customers Now this isn't complex at all. With the help of some cool tools (CMapTools), I drew out some concepts, but quickly enough (thanks to my inferior experience in designing), my design started to bite me. My very first product-line were virtual "laptops". So, I created a class (Ruby): class Product attr_accessor :name, :price def initialize(name, price) @name = name @price = price end end which can be instantiated by doing (IRb) x = Product.new("Banana Pro", 250) Since I want my virtual customers to be able to purchase more than one product, or various types, I figured out I needed some kind of "Order" mechanism. class Order def initialize(order_no) @order_no = order_no @line_items = [] end def add_product(myproduct) @line_items << myproduct end def show_order() puts @order_no @line_items.each do |x| puts x.name.to_s + "\t" + x.price.to_s end end end that can be instantiated by doing (IRb) z = Order.new(1234) z.add_product(x) z.show_order Splendid, I have now a very simple ordering system that allows me to add products to an order. But, here comes my real question. What if I have three models of my product (economy, business, showoff)? Or have my products be composed out of separate units (bigger screen, nicer keyboard, different OS)? Surely I could make them three separate products, or add complexity to my product class, but I am looking for are best practices to design a flexible product object that can be used in the real world, to facilitate a complex system. My apologies if my grammar and my spelling are with error, as english is not my first language and I took the time to check as far I could understand and translate properly! Thank you for your answers, comments and feedback!

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• Is learning C++ a good idea?

  - by chang

  The more I hear and read about C++ (e.g. this: http://lwn.net/Articles/249460/), I get the impression, that I'd waste my time learning C++. I some wrote network routing algorithm in C++ for a simulator, and it was a pain (as expected, especially coming from a perl/python/Java background ...). I'm never happy about giving up on some technology, but I would be happy, if I could limit my knowledge of C-family languages to just C, C# and Objective-C (even OS Xs Cocoa, which is huge and takes a lot of time to learn looks like joy compared to C++ ...). Do I need to consider myself dumb or unwilling, just because I'm not partial to the pain involved learning this stuff? Technologies advance and there will be options other than C++, when deciding on implementation languages, or not? And for speed: If speed were that critical, I'd go for a plain C implementation instead, or write C extensions for much more productive languages like ruby or python ... The one-line version of the above: Will C++ stay such a relevant language that every committed programmer should be familiar with it? [ edit / thank you very much for your interesting and useful answers so far .. ] [ edit / .. i am accepting the top-rated answer; thanks again for all answers! ]

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• L-Soft LISTSERV TCPGUI Interface for PHP Creation

  - by poolnoodl

  I'm trying to use LISTSERV's "API" in PHP. L-Soft calls this TCPGUI, and essentially, you can request data like over Telnet. To do this, I'm using PHP's TCP socket functions. I've seen this done in other languages but can't quite convert it to PHP. I can connect, I can change set ASCII or BINARY mode. But I can never quite craft the header packet the way I need to authenticate, so I'm thinking I'm messing up my conversion. C: http://www.lsoft.com/manuals/16.0/htmlhelp/advanced%20topics/TCPGUI.html#2334328 $origin = '[email protected]'; $pwd = 'password'; $host = "example.com"; $port = 2306; $email = "[email protected]"; $list = "mailinglist"; $command = "Query $list FOR $email"; $fp = stream_socket_client("tcp://$host:$port", $errno, $errstr, 30); $cmd = $command . " PW=" . $pwd; $len = strlen($cmd); $orglen = strlen($origin); $n = $len + $orglen + 1; $headerPacket[0] = "1"; $headerPacket[1] = "B"; $headerPacket[2] = "\r"; $headerPacket[3] = "\n"; $headerPacket[4] = ord($n / 256); $headerPacket[5] = ord($n + 255); $headerPacket[6] = ord($orglen); for ($i = 0; $i < $orglen; $i++) { $headerPacket[$i + 7] = ord($origin[$i]); } for ($i = 0; $i < $len; $i++) { $cmdPacket[$i] = ord($cmd[$i]); } fwrite($fp, implode($headerPacket)); while (!feof($fp)) { echo fgets($fp, 1024); } Any thoughts on where I'm going wrong? I'd much appreciate it if anyone could point me toward some code to do this, days of googling and searching here on SO has only lead me to examples in other languages. Of course, if you know C (or Java or Perl as linked below in my comment to bypass the spam filter), PHP, and socket programming fairly well, you could probably rewrite the whole of the code in an hour, maybe a few minutes. You'd have my eternal thanks for that.

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• Java - is this an idiom or pattern, behavior classes with no state

  - by Berlin Brown

  I am trying to incorporate more functional programming idioms into my java development. One pattern that I like the most and avoids side effects is building classes that have behavior but they don't necessarily have any state. The behavior is locked into the methods but they only act on the parameters passed in. The code below is code I am trying to avoid: public class BadObject { private Map<String, String> data = new HashMap<String, String>(); public BadObject() { data.put("data", "data"); } /** * Act on the data class. But this is bad because we can't * rely on the integrity of the object's state. */ public void execute() { data.get("data").toString(); } } The code below is nothing special but I am acting on the parameters and state is contained within that class. We still may run into issues with this class but that is an issue with the method and the state of the data, we can address issues in the routine as opposed to not trusting the entire object. Is this some form of idiom? Is this similar to any pattern that you use? public class SemiStatefulOOP { /** * Private class implies that I can access the members of the <code>Data</code> class * within the <code>SemiStatefulOOP</code> class and I can also access * the getData method from some other class. * * @see Test1 * */ class Data { protected int counter = 0; public int getData() { return counter; } public String toString() { return Integer.toString(counter); } } /** * Act on the data class. */ public void execute(final Data data) { data.counter++; } /** * Act on the data class. */ public void updateStateWithCallToService(final Data data) { data.counter++; } /** * Similar to CLOS (Common Lisp Object System) make instance. */ public Data makeInstance() { return new Data(); } } // End of Class // Issues with the code above: I wanted to declare the Data class private, but then I can't really reference it outside of the class: I can't override the SemiStateful class and access the private members. Usage: final SemiStatefulOOP someObject = new SemiStatefulOOP(); final SemiStatefulOOP.Data data = someObject.makeInstance(); someObject.execute(data); someObject.updateStateWithCallToService(data);

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• Derived template override return type of member function C++

  - by Ruud v A

  I am writing matrix classes. Take a look at this definition: template <typename T, unsigned int dimension_x, unsigned int dimension_y> class generic_matrix { ... generic_matrix<T, dimension_x - 1, dimension_y - 1> minor(unsigned int x, unsigned int y) const { ... } ... } template <typename T, unsigned int dimension> class generic_square_matrix : public generic_matrix<T, dimension, dimension> { ... generic_square_matrix(const generic_matrix<T, dimension, dimension>& other) { ... } ... void foo(); } The generic_square_matrix class provides additional functions like matrix multiplication. Doing this is no problem: generic_square_matrix<T, 4> m = generic_matrix<T, 4, 4>(); It is possible to assign any square matrix to M, even though the type is not generic_square_matrix, due to the constructor. This is possible because the data does not change across children, only the supported functions. This is also possible: generic_square_matrix<T, 4> m = generic_square_matrix<T, 5>().minor(1,1); Same conversion applies here. But now comes the problem: generic_square_matrix<T, 4>().minor(1,1).foo(); //problem, foo is not in generic_matrix<T, 3, 3> To solve this I would like generic_square_matrix::minor to return a generic_square_matrix instead of a generic_matrix. The only possible way to do this, I think is to use template specialisation. But since a specialisation is basically treated like a separate class, I have to redefine all functions. I cannot call the function of the non-specialised class as you would do with a derived class, so I have to copy the entire function. This is not a very nice generic-programming solution, and a lot of work. C++ almost has a solution for my problem: a virtual function of a derived class, can return a pointer or reference to a different class than the base class returns, if this class is derived from the class that the base class returns. generic_square_matrix is derived from generic_matrix, but the function does not return a pointer nor reference, so this doesn't apply here. Is there a solution to this problem (possibly involving an entirely other structure; my only requirements are that the dimensions are a template parameter and that square matrices can have additional functionality). Thanks in advance, Ruud

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• What's the purpose of arrays starting with nonzero index?

  - by helios35

  I tried to find answers, but all I got was answers on how to realize arrays starting with nonzero indexes. Some languages, such as pascal, provide this by default, e.g., you can create an array such as var foobar: array[1..10] of string; I've always been wondering: Why would you want to have the array index not to start with 0? I guess it may be more familiar for beginners to have arrays starting with 1 and the last index being the size of the array, but on a long-term basis, programmers should get used to values starting with 0. Another purpose I could think of: In some cases, the index could actually represent something thats contained in the respective array-entry. e.g., you want to get all capital letters in an array, it may be handy to have an index being the ASCII-Code of the respective letter. But its pretty easy just to subtract a constant value. In this example, you could (in C) simply do something like this do get all capital letters and access the letter with ascii-code 67: #define ASCII_SHIFT 65 main() { int capital_letters[26]; int i; for (i=0; i<26; i++){ capital_letters[i] = i+ASCII_SHIFT; } printf("%c\n", capital_letters[67-ASCII_SHIFT]); } Also, I think you should use hash tables if you want to access entries by some sort of key. Someone might retort: Why should the index always start with 0? Well, it's a hell of a lot simpler this way. You'll be faster when you just have to type one index when declaring an array. Also, you can always be sure that the first entry is array[0] and the last one is array[length_of_array-1]. It is also common that other data structures start with 0. e.g., if you read a binary file, you start with the 0th byte, not the first. Now, why do some programming languages have this "feature" and why do some people ask how to achieve this in languages such as C/C++?, is there any situation where an array starting with a nonzero index is way more useful, or even, something simply cannot be done with an array starting at 0?

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• Why does my ping command (Windows) results alternate between "timeout" and "network is not reachable"?

  - by Sopalajo de Arrierez

  My Windows is in Spanish, so I will have to paste console outputs in that language (I think that translating without knowing the exact terms used in english versions could give worse results than leaving it as it appears on screen). This is the issue: when pinging a non-existent IP from a WinXP-SP3 machine (clean Windows install, just formatted), I get sometimes a "Timeout" result, and sometimes a "network is not reachable" message. This is the result of: ping 192.168.210.1 Haciendo ping a 192.168.210.1 con 32 bytes de datos: Tiempo de espera agotado para esta solicitud. Respuesta desde 80.58.67.86: Red de destino inaccesible. Respuesta desde 80.58.67.86: Red de destino inaccesible. Tiempo de espera agotado para esta solicitud. Estadísticas de ping para 192.168.210.1: Paquetes: enviados = 4, recibidos = 2, perdidos = 2 (50% perdidos), Tiempos aproximados de ida y vuelta en milisegundos: Mínimo = 0ms, Máximo = 0ms, Media = 0ms 192.168.210.1 does not exist on the network. DHCP client is enabled, and the computer gets assigned those network config by the router. My IP: 192.168.11.2 Netmask: 255.255.255.0 Gateway: 192.168.11.1 DNS: 80.58.0.33/194.224.52.36 This is the output from "route print command": =========================================================================== Rutas activas: Destino de red Máscara de red Puerta de acceso Interfaz Métrica 0.0.0.0 0.0.0.0 192.168.11.1 192.168.11.2 20 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.11.0 255.255.255.0 192.168.11.2 192.168.11.2 20 192.168.11.2 255.255.255.255 127.0.0.1 127.0.0.1 20 192.168.11.255 255.255.255.255 192.168.11.2 192.168.11.2 20 224.0.0.0 240.0.0.0 192.168.11.2 192.168.11.2 20 255.255.255.255 255.255.255.255 192.168.11.2 192.168.11.2 1 255.255.255.255 255.255.255.255 192.168.11.2 3 1 Puerta de enlace predeterminada: 192.168.11.1 =========================================================================== Rutas persistentes: ninguno The output of: ping 1.1.1.1 Haciendo ping a 1.1.1.1 con 32 bytes de datos: Tiempo de espera agotado para esta solicitud. Tiempo de espera agotado para esta solicitud. Tiempo de espera agotado para esta solicitud. Tiempo de espera agotado para esta solicitud. Estadísticas de ping para 1.1.1.1: Paquetes: enviados = 4, recibidos = 0, perdidos = 4 1.1.1.1 does not exist on the network. and the output of: ping 10.1.1.1 Haciendo ping a 10.1.1.1 con 32 bytes de datos: Respuesta desde 80.58.67.86: Red de destino inaccesible. Tiempo de espera agotado para esta solicitud. Tiempo de espera agotado para esta solicitud. Respuesta desde 80.58.67.86: Red de destino inaccesible. Estadísticas de ping para 10.1.1.1: Paquetes: enviados = 4, recibidos = 2, perdidos = 2 (50% perdidos), 10.1.1.1 does not exist on the network. I can do some aproximate translation of what you demand if necessary. I have another computers in the same network (WinXP-SP3 and Win7-SP1), and they have, too, this problem. Gateway (Router): Buffalo WHR-HP-GN (official Buffalo firmware, not DD-WRT). I have some Linux (Debian/Kali) machine in my network, so I tested things on it: ping 192.168.210.1 PING 192.168.210.1 (192.168.210.1) 56(84) bytes of data. From 80.58.67.86 icmp_seq=1 Packet filtered From 80.58.67.86 icmp_seq=2 Packet filtered From 80.58.67.86 icmp_seq=3 Packet filtered From 80.58.67.86 icmp_seq=4 Packet filtered to the non-existing 1.1.1.1 : ping 1.1.1.1 PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data. ^C --- 1.1.1.1 ping statistics --- 153 packets transmitted, 0 received, 100% packet loss, time 153215ms (no response after waiting a few minutes). and the non-existing 10.1.1.1: ping 10.1.1.1 PING 10.1.1.1 (10.1.1.1) 56(84) bytes of data. From 80.58.67.86 icmp_seq=20 Packet filtered From 80.58.67.86 icmp_seq=22 Packet filtered From 80.58.67.86 icmp_seq=23 Packet filtered From 80.58.67.86 icmp_seq=24 Packet filtered From 80.58.67.86 icmp_seq=25 Packet filtered What is going on here? I am posing this question mainly for learning purposes, but there is another reason: when all pings are returning "timeout", it creates an %ERRORLEVEL% value of 1, but if there is someone of "Network is not reachable" type, %ERRORLEVEL% goes to 0 (no error), and this could be inappropriate for a shell script (we can not use ping to detect, for example, if the network is down due to loss of contact with the gateway).

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