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• Can a class inherit from LambdaExpression in .NET? Or is this not recommended?

  - by d.

  Consider the following code (C# 4.0): public class Foo : LambdaExpression { } This throws the following design-time error: Foo does not implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) There's absolutely no problem with public class Foo : Expression { } but, out of curiosity and for the sake of learning, I've searched in Google System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) and guess what: zero results returned (when was the last time you saw that?). Needless to say, I haven't found any documentation on this method anywhere else. As I said, one can easily inherit from Expression; on the other hand LambdaExpression, while not marked as sealed (Expression<TDelegate> inherits from it), seems to be designed to prevent inheriting from it. Is this actually the case? Does anyone out there know what this method is about? EDIT (1): More info based on the first answers - If you try to implement Accept, the editor (C# 2010 Express) automatically gives you the following stub: protected override Expression Accept(System.Linq.Expressions.ExpressionVisitor visitor) { return base.Accept(visitor); } But you still get the same error. If you try to use a parameter of type StackSpiller directly, the compiler throws a different error: System.Linq.Expressions.Compiler.StackSpiller is inaccessible due to its protection level. EDIT (2): Based on other answers, inheriting from LambdaExpression is not possible so the question as to whether or not it is recommended becomes irrelevant. I wonder if, in cases like this, the error message should be Foo cannot implement inherited abstract member System.Linq.Expressions.LambdaExpression.Accept(System.Linq.Expressions.Compiler.StackSpiller) because [reasons go here]; the current error message (as some answers prove) seems to tell me that all I need to do is implement Accept (which I can't do).

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• Bash: how to simply parallelize tasks?

  - by NoozNooz42

  I'm writing a tiny script that calls the "PNGOUT" util on a few hundred PNG files. I simply did this: find $BASEDIR -iname "*png" -exec pngout {} \; And then I looked at my CPU monitor and noticed only one of the core was used, which is quite sad. In this day and age of dual, quad, octo and hexa (?) cores desktop, how do I simply parallelize this task with Bash? (it's not the first time I've had such a need, for quite a lot of these utils are mono-threaded... I already had the case with mp3 encoders). Would simply running all the pngout in the background do? How would my find command look like then? (I'm not too sure how to mix find and the '&' character) I if have three hundreds pictures, this would mean swapping between three hundreds processes, which doesn't seem great anyway!? Or should I copy my three hundreds files or so in "nb dirs", where "nb dirs" would be the number of cores, then run concurrently "nb finds"? (which would be close enough) But how would I do this?

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• Use external datasource with NUnit's TestCaseAttribute

  - by Hamman359

  Is it possible to get the values for a TestCaseAttribute from an external data source such as an Excel Spreadsheet, CSV file or Database? i.e. Have a .csv file with 1 row of data per test case and pass that data to NUnit one at a time. Here's the specific situation that I'd like to use this for. I'm currently merging some features from one system into another. This is pretty much just a copy and paste process from the old system into the new one. Unfortunately, the code being moved not only does not have any tests, but is not written in a testable manner (i.e. tightly coupled with the database and other code.) Taking the time to make the code testable isn't really possible since its a big mess, i'm on a tight schedule and the entire feature is scheduled to be re-written from the ground up in the next 6-9 months. However, since I don't like the idea of not having any tests around the code, I'm going to create some simple Selenium tests using WebDriver to test the page through the UI. While this is not ideal, it's better than nothing. The page in question has about 10 input values and about 20 values that I need to assert against after the calculations are completed, with about 30 valid combinations of values that I'd like to test. I already have the data in a spreadsheet so it'd be nice to simply be able to pull that out rather than having to re-type it all in Visual Studio.

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• In Java, howd do I iterate through lines in a textfile from back to front

  - by rogue780

  Basically I need to take a text file such as : Fred Bernie Henry and be able to read them from the file in the order of Henry Bernie Fred The actual file I'm reading from is 30MB and it would be a less than perfect solution to read the whole file, split it into an array, reverse the array and then go from there. It takes way too long. My specific goal is to find the first occurrence of a string (in this case it's "InitGame") and then return the position beginning of the beginning of that line. I did something like this in python before. My method was to seek to the end of the file - 1024, then read lines until I get to the end, then seek another 1024 from my previous starting point and, by using tell(), I would stop when I got to the previous starting point. So I would read those blocks backwards from the end of the file until I found the text I was looking for. So far, I'm having a heck of a time doing this in Java. Any help would be greatly appreciated and if you live near Baltimore it may even end up with you getting some fresh baked cookies. Thanks!

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• auto m3u creation

  - by newbie69

  Hi, I am looking for a solution to automatically create .m3u playlists for each music folder in my sdcard so that the music player can play music by folders. I had written a simple VB.Net app in the past that does exactly the above but apparently, it has to be run from Windows. Since I have no Java nor Android developing experience I found it quite hard to try to write a similar app that can be run directly from the phone. In a few words, the app does the following: 1) Searches the SD and lists all folders that contain 2 or more .mp3 files (just for user verification) 2) Creates in every listed folder above, a .m3u file that simply lists line-by-line all the mp3 files that exist in the specific folder. Is there such an app or could someone spare some time and give me some rough instructions on how to create it in Eclipse 3.5.2 environment? (device used: Motorola Droid/Milestone, Android 2.1) I don't care about any graphics or complex UI, just a script to execute the above procedure that would give every "playlist-supporting" music player in Android, the precious ability to play music by folders. I know it is too much to ask but just in case! Thanx in advance.

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• Why do IOExceptions occur in ReadableByteChannel.read()

  - by Steffen Heil

  Hi The specification of ReadableByteChannel.read() shows -1 as result value for end-of-stream. Moreover it specifies ClosedByInterruptExceptionas possible result if the thread is interrupted. Now I thought that would be all - and it is most of the time. However, now and then I get the following: java.io.IOException: Eine vorhandene Verbindung wurde vom Remotehost geschlossen at sun.nio.ch.SocketDispatcher.read0(Native Method) at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:25) at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:233) at sun.nio.ch.IOUtil.read(IOUtil.java:206) at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:236) at ... I do not unterstand why I don't get -1 in this case. Also this is not a clean exception, as I cannot catch it without catching any possible IOException. So here are my questions: Why is this exception thrown in the first place? Is it safe to assume that ANY exception thrown by read are about the socket being closed? Is all this the same for write()? And by the way: If I call SocketChannel.close() do I have to call SocketChannel.socket().close() as well or is this implied by the earlier? Thanks, Steffen

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• Multithreaded IOCP Client Issue

  - by Carl

  I am writing a multithreaded client that uses an IO Completion Port. I create and connect the socket that has the WSA_FLAG_OVERLAPPED attribute set. if ((m_socket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET) { throw std::exception("Failed to create socket."); } if (WSAConnectByName(m_socket, L"server.com", L"80", &localAddressLength, reinterpret_cast<sockaddr*>(&localAddress), &remoteAddressLength, &remoteAddress, NULL, NULL) == FALSE) { throw std::exception("Failed to connect."); } I associate the IO Completion Port with the socket. if ((m_hIOCP = CreateIoCompletionPort(reinterpret_cast<HANDLE>(m_socket), m_hIOCP, NULL, 8)) == NULL) { throw std::exception("Failed to create IOCP object."); } All appears to go well until I try to send some data over the socket. SocketData* socketData = new SocketData; socketData->hEvent = 0; DWORD bytesSent = 0; if (WSASend(m_socket, socketData->SetBuffer(socketData->GenerateLoginRequestHeader()), 1, &bytesSent, NULL, reinterpret_cast<OVERLAPPED*>(socketData), NULL) == SOCKET_ERROR && WSAGetLastError() != WSA_IO_PENDING) { throw std::exception("Failed to send data."); } Instead of returning SOCKET_ERROR with the last error set to WSA_IO_PENDING, WSASend returns immediately. I need the IO to pend and for it's completion to be handled in my thread function which is also my worker thread. unsigned int __stdcall MyClass::WorkerThread(void* lpThis) { } I've done this before but I don't know what is going wrong in this case, I'd greatly appreciate any efforts in helping me fix this problem.

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• HTTP crawler in Erlang

  - by ctp

  I'm coding on a simple HTTP crawler but I have an issue running the code at the bottom. I'm requesting 50 URLs and get the content of 20+ back. I've generated few files with 150kB size each to test the crawler. So I think the 20+ responses are limited by the bandwidth? BUT: how to tell the Erlang snippet not to quit until the last file is not fetched? The test data server is online, so plz try the code out and any hints are welcome :) -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/1]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> lists:foreach(fun do_spawn/1, Ids). do_spawn(Id) -> proc_lib:spawn_link(?MODULE, do_send_req, [Id]). do_send_req(Id) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]); Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]) end. That's the output: Requesting ID 1 ... Requesting ID 2 ... Requesting ID 3 ... Requesting ID 4 ... Requesting ID 5 ... Requesting ID 6 ... Requesting ID 7 ... Requesting ID 8 ... Requesting ID 9 ... Requesting ID 10 ... Requesting ID 11 ... Requesting ID 12 ... Requesting ID 13 ... Requesting ID 14 ... Requesting ID 15 ... Requesting ID 16 ... Requesting ID 17 ... Requesting ID 18 ... Requesting ID 19 ... Requesting ID 20 ... Requesting ID 21 ... Requesting ID 22 ... Requesting ID 23 ... Requesting ID 24 ... Requesting ID 25 ... Requesting ID 26 ... Requesting ID 27 ... Requesting ID 28 ... Requesting ID 29 ... Requesting ID 30 ... Requesting ID 31 ... Requesting ID 32 ... Requesting ID 33 ... Requesting ID 34 ... Requesting ID 35 ... Requesting ID 36 ... Requesting ID 37 ... Requesting ID 38 ... Requesting ID 39 ... Requesting ID 40 ... Requesting ID 41 ... Requesting ID 42 ... Requesting ID 43 ... Requesting ID 44 ... Requesting ID 45 ... Requesting ID 46 ... Requesting ID 47 ... Requesting ID 48 ... Requesting ID 49 ... Requesting ID 50 ... OK -- ID: 49 -- Status: "200" -- Content length: 150000 OK -- ID: 47 -- Status: "200" -- Content length: 150000 OK -- ID: 50 -- Status: "200" -- Content length: 150000 OK -- ID: 17 -- Status: "200" -- Content length: 150000 OK -- ID: 48 -- Status: "200" -- Content length: 150000 OK -- ID: 45 -- Status: "200" -- Content length: 150000 OK -- ID: 46 -- Status: "200" -- Content length: 150000 OK -- ID: 10 -- Status: "200" -- Content length: 150000 OK -- ID: 09 -- Status: "200" -- Content length: 150000 OK -- ID: 19 -- Status: "200" -- Content length: 150000 OK -- ID: 13 -- Status: "200" -- Content length: 150000 OK -- ID: 21 -- Status: "200" -- Content length: 150000 OK -- ID: 16 -- Status: "200" -- Content length: 150000 OK -- ID: 27 -- Status: "200" -- Content length: 150000 OK -- ID: 03 -- Status: "200" -- Content length: 150000 OK -- ID: 23 -- Status: "200" -- Content length: 150000 OK -- ID: 29 -- Status: "200" -- Content length: 150000 OK -- ID: 14 -- Status: "200" -- Content length: 150000 OK -- ID: 18 -- Status: "200" -- Content length: 150000 OK -- ID: 01 -- Status: "200" -- Content length: 150000 OK -- ID: 30 -- Status: "200" -- Content length: 150000 OK -- ID: 40 -- Status: "200" -- Content length: 150000 OK -- ID: 05 -- Status: "200" -- Content length: 150000 Update: thanks stemm for the hint with the wait_workers. I've combined your and mine code but same behaviour :( -module(crawler). -define(BASE_URL, "http://46.4.117.69/"). -export([start/0, send_reqs/0, do_send_req/2]). start() -> ibrowse:start(), proc_lib:spawn(?MODULE, send_reqs, []). to_url(Id) -> ?BASE_URL ++ integer_to_list(Id). fetch_ids() -> lists:seq(1, 50). send_reqs() -> spawn_workers(fetch_ids()). spawn_workers(Ids) -> %% collect reference to each worker Refs = [ do_spawn(Id) || Id <- Ids ], %% wait for response from each worker wait_workers(Refs). wait_workers(Refs) -> lists:foreach(fun receive_by_ref/1, Refs). receive_by_ref(Ref) -> %% receive message only from worker with specific reference receive {Ref, done} -> done end. do_spawn(Id) -> Ref = make_ref(), proc_lib:spawn_link(?MODULE, do_send_req, [Id, {self(), Ref}]), Ref. do_send_req(Id, {Pid, Ref}) -> io:format("Requesting ID ~p ... ~n", [Id]), Result = (catch ibrowse:send_req(to_url(Id), [], get, [], [], 10000)), case Result of {ok, Status, _H, B} -> io:format("OK -- ID: ~2..0w -- Status: ~p -- Content length: ~p~n", [Id, Status, length(B)]), %% send message that work is done Pid ! {Ref, done}; Err -> io:format("ERROR -- ID: ~p -- Error: ~p~n", [Id, Err]), %% repeat request if there was error while fetching a page, do_send_req(Id, {Pid, Ref}) %% or - if you don't want to repeat request, put there: %% Pid ! {Ref, done} end. Running the crawler forks fine for a handful of files, but then the code even doesnt fetch the entire files (file size each 150000 bytes) - he crawler fetches some files partially, see the following web server log :( 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /10 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /1 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /3 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /8 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /39 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /7 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /6 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /2 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /5 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /50 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /9 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /44 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /38 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /47 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /49 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /43 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /37 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /46 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /48 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:00 +0200] "GET /36 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /42 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /41 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /45 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /17 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /35 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /16 HTTP/1.1" 200 150000 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /15 HTTP/1.1" 200 17020 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /21 HTTP/1.1" 200 120360 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /40 HTTP/1.1" 200 117600 "-" "-" 82.114.62.14 - - [13/Sep/2012:15:17:01 +0200] "GET /34 HTTP/1.1" 200 60660 "-" "-" Any hints are welcome. I have no clue what's going wrong there :(

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• Why use INCLUDE in a SQL index

  - by StarLite

  I recently encountered an index in a database I maintain that was of the form: CREATE INDEX [IX_Foo] ON [Foo] ( Id ASC ) INCLUDE ( SubId ) In this particular case, the performance problem that I was encountering (a slow SELECT filtering on both Id and SubId) could be fixed by simply moving the SubId column into the index proper rather than as an included column. This got me thinking however that I don't understand the reasoning behind included columns at all, when generally, they could simply be a part of the index itself. Even if I don't particularly care about the items being in the index itself is there any downside to having column in the index rather than simply being included. After some research, I am aware that there are a number of restrictions on what can go into an indexed column (maximum width of the index, and some column types that can't be indexed like 'image'). In these cases I can see that you would be forced to include the column in the index page data. The only thing I can think of is that if there are updates on SubId, the row will not need to be relocated if the column is included (though the value in the index would need to be changed). Is there something else that I'm missing? I'm considering going through the other indexes in the database and shifting included columns in the index proper where possible. Would this be a mistake? I'm primarily interested in MS SQL Server, but information on other DB engines is welcome also.

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• .NET RegEx - First N chars of First M lines

  - by George

  Hello! I want 4 general RegEx expressions for the following 4 basic cases: Up to A chars starting after B chars from start of line on up to C lines starting after D lines from start of file Up to A chars starting after B chars from start of line on up to C lines occurring before D lines from end of file Up to A chars starting before B chars from end of line on up to C lines starting after D lines from start of file Up to A chars starting before B chars from end of line on up to C lines starting before D lines from end of file These would allow to select arbitrary text blocks anywhere in the file. So far I have managed to come up with cases that only work for lines and chars separately: (?<=(?m:^[^\r]{N}))[^\r]{1,M} = UP TO M chars OF EVERY LINE, AFTER FIRST N chars [^\r]{1,M}(?=(?m:.{N}\r$)) = UP TO M chars OF EVERY LINE, BEFORE LAST N chars The above 2 expressions are for chars, and they return MANY matches (one for each line). (?<=(\A([^\r]*\r\n){N}))(?m:\n*[^\r]*\r$){1,M} = UP TO M lines AFTER FIRST N lines (((?=\r?)\n[^\r]*\r)|((?=\r?)\n[^\r]+\r?)){1,M}(?=((\n[^\r]*\r)|(\n[^\r]+\r?)){N}\Z) = UP TO M lines BEFORE LAST N lines from end These 2 expressions are equivalents for the lines, but they always return just ONE match. The task is to combine these expressions to allow for scenarios 1-4. Anyone can help? Note that the case in the title of the question, is just a subclass of scenario #1, where both B = 0 and D = 0. EXAMPLE: SOURCE: line1 blah 1 line2 blah 2 line3 blah 3 line4 blah 4 line5 blah 5 line6 blah 6 DESIRED RESULT: Characters 3-6 of lines 3-5: A total of 3 matches: <match>ne3 </match> <match>ne4 </match> <match>ne5 </match>

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• Problem with GWT behind a reverse proxy - either nginx or apache

  - by Don Branson

  I'm having this problem with GWT when it's behind a reverse proxy. The backend app is deployed within a context - let's call it /context. The GWT app works fine when I hit it directly: http://host:8080/context/ I can configure a reverse proxy in front it it. Here's my nginx example: upstream backend { server 127.0.0.1:8080; } ... location / { proxy_pass http://backend/context/; } But, when I run through the reverse proxy, GWT gets confused, saying: 2009-10-04 14:05:41.140:/:WARN: Login: ERROR: The serialization policy file '/C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.140:/:WARN: Login: WARNING: Failed to get the SerializationPolicy 'C7F5ECA5E3C10B453290DE47D3BE0F0E' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. 2009-10-04 14:05:41.292:/:WARN: StoryService: ERROR: The serialization policy file '/0445C2D48AEF2FB8CB70C4D4A7849D88.gwt.rpc' was not found; did you forget to include it in this deployment? 2009-10-04 14:05:41.292:/:WARN: StoryService: WARNING: Failed to get the SerializationPolicy '0445C2D48AEF2FB8CB70C4D4A7849D88' for module 'https://hostname:444/'; a legacy, 1.3.3 compatible, serialization policy will be used. You may experience SerializationExceptions as a result. In other words, GWT isn't getting the word that it needs to prepend /context/ hen look for C7F5ECA5E3C10B453290DE47D3BE0F0E.gwt.rpc, but only when the request comes throught proxy. A workaround is to add the context to the url for the web site: location /context/ { proxy_pass http://backend/context/; } but that means the context is now part of the url that the user sees, and that's ugly. Anybody know how to make GWT happy in this case? Software versions: GWT - 1.7.0 (same problem with 1.7.1) Jetty - 6.1.21 (but the same problem existed under tomcat) nginx - 0.7.62 (same problem under apache 2.x) I've looked at the traffic between the proxy and the backend using DonsProxy, but there's nothing noteworthy there.

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• What harm can javascript do?

  - by The King

  I just happen to read the joel's blog here... So for example if you have a web page that says “What is your name?” with an edit box and then submitting that page takes you to another page that says, Hello, Elmer! (assuming the user’s name is Elmer), well, that’s a security vulnerability, because the user could type in all kinds of weird HTML and JavaScript instead of “Elmer” and their weird JavaScript could do narsty things, and now those narsty things appear to come from you, so for example they can read cookies that you put there and forward them on to Dr. Evil’s evil site. Since javascript runs on client end. All it can access or do is only on the client end. It can read informations stored in hidden fields and change them. It can read, write or manipulate cookies... But I feel, these informations are anyway available to him. (if he is smart enough to pass javascript in a textbox. So we are not empowering him with new information or providing him undue access to our server... Just curious to know whether I miss something. Can you list the things that a malicious user can do with this security hole. Edit : Thanks to all for enlightening . As kizzx2 pointed out in one of the comments... I was overlooking the fact that a JavaScript written by User A may get executed in the browser of User B under numerous circumstances, in which case it becomes a great risk.

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• Is ASP.NET MVC is really MVC? Or how to separate model from controller?

  - by Andrey

  Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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• How to nest shapes in a DSL Tools diagram?

  - by Paul Lalonde

  I have a DSL containing two main domain classes: Area and Entity. Areas are represented visually by a GeometryShape, whereas entities are represented by a CompartmentShape. Entities can be embedded in an Area, or not (in this case they are embedded in the root object, which is a kind of Area). There may be relationships between entities, including between entities in different areas. Areas cannot be embedded inside of other areas, nor entities embedded inside of other entities. My problem is that I cannot get the behavior I want from the diagram. The embedding of entities in areas works perfectly well at the model level, but the visual representation behaves erratically. For example, if I drag an entity that was created in an area outside of that area, it no longer responds to mouse clicks (I have code that performs the re-parenting, but somehow the diagram side of things is broken). I have searched high and low for samples of how to do this, and come up empty. Every example I've found on the web simulates nesting via "references" relationships, whereas I am performing true embedding of the domain classes (and therefore of their associated shape classes). Does anyone have an example of how to do this? While I'm venting, am I the only one who thinks the diagram/shape classes are massively under-documented?

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• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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• Flex 3 - Issues with textArea "editable" property

  - by BS_C3

  Hello Community! I'm having issues with the property "editable" of textArea control. I have a component: OrderView.mxml and it's associated data class OrderViewData.as. Orderview.mxml is inside a viewStack to enable navigation from a component to another. In this particular case, OrderView.mxml is called by another component: SearchResult.mxml. I can thus navigate from SearchResult.mxml to OrderView.mxml, and back to SearchResult.mxml... OrderView.mxml has textArea and textInput control, that have to be editable or nonEditable depending on the property var isEditable:Boolean from OrderViewData.as. When the application is launched, isEditable = true. So, all textInput and textArea controls are editable the first time the user gets to OrderView.mxml. When the user clicks on the button order from OrderView.mxml, isEditable = false. When the user goes back to SearchResult.mxml, isEditable = true (again) -- Until here, everything works fine. The thing is: when the user goes back to OrderView.mxml for the second time (and beyond), even if the property isEditable = true, textArea controls are still non editable... But the textInput controls are editable! Here is some code for your comprehension: OrderView.mxml <mx:Canvas xmlns:mx="http://www.adobe.com/2006/mxml" backgroundColor="#F3EDEC"> <mx:TextArea id="contentTA" text="{OrderViewData.instance.contentTA}" enabled="{OrderViewData.instance.isEnabled}" width="100%" height="51" maxChars="18" styleName="ORTextInput" focusIn="if(OrderViewData.instance.isEditable) contentTA.setSelection(0, contentTA.length)"/> <mx:TextInput id="contentTI" text="{OrderViewData.instance.contentTI}" width="40" height="18" maxChars="4" styleName="ORTextInput" change="contentTI_change()" focusIn="if(OrderViewData.instance.isEditable) contentTI.setSelection(0, contentTI.length)" editable="{OrderViewData.instance.isEditable}"/> </mx:Canvas> Am I missing something? Thanks for any help you can provide. Regards. BS_C3

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• How does this code break the Law of Demeter?

  - by Dave Jarvis

  The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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• Algorithm to see if keywords exist inside a string

  - by rksprst

  Let's say I have a set of keywords in an array {"olympics", "sports tennis best", "tennis", "tennis rules"} I then have a large list (up to 50 at a time) of strings (or actually tweets), so they are a max of 140 characters. I want to look at each string and see what keywords are present there. In the case where a keyword is composed of multiple words like "sports tennis best", the words don't have to be together in the string, but all of them have to show up. I've having trouble figuring out an algorithm that does this efficiently. Do you guys have suggestions on a way to do this? Thanks! Edit: To explain a bit better each keyword has an id associated with it, so {1:"olympics", 2:"sports tennis best", 3:"tennis", 4:"tennis rules"} I want to go through the list of strings/tweets and see which group of keywords match. The output should be, this tweet belongs with keyword #4. (multiple matches may be made, so anything that matches keyword 2, would also match 3 -since they both contain tennis). When there are multiple words in the keyword, e.g. "sports tennis best" they don't have to appear together but have to all appear. e.g. this will correctly match: "i just played tennis, i love sports, its the best"... since this string contains "sports tennis best" it will match and be associated with the keywordID (which is 2 for this example).

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• DQL delete from multiple tables (doctrine)

  - by singer

  Need to perform DQL delete from multple related tables. In SQL it is something like this: DELETE r1,r2 FROM ComRealty_objects r1, com_realty_objects_phones r2 WHERE r1.id IN (10,20) AND r2.id_object IN (10,20) I need to perform this statement using DQL, but I'm stuck on this :( <?php $dql = Doctrine_Query::create() ->delete('phones, comrealtyobjects') ->from('ComRealtyObjects comrealtyobjects') ->from('ComRealtyObjectsPhones phones') ->whereIn("comrealtyobjects.id", $ids) ->whereIn("phones.id_object", $ids); echo($dql->getSqlQuery()); ?> But DQL parser gives me this result: DELETE FROM `com_realty_objects_phones`, `ComRealty_objects` WHERE (`id` IN (?) AND `id_object` IN (?)) Searching google and stack overflow I found this(useful) topic: http://stackoverflow.com/questions/2247905/what-is-the-syntax-for-a-multi-table-delete-on-a-mysql-database-using-doctrine But this is not exactly my case - there was delete from single table. If there is a way to override dql parser behaviour? Or maybe some other way to delete records from multiple tables using doctrine. Note: If you are using doctrine behaviours(Doctrine_Record_Generator) you need first to initialize those tables using Doctrine_Core::initializeModels() to perform DQL operations on them.

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• Prevent deferred creation of controls.

  - by Scott Chamberlain

  Here is a test framework to show what I am doing, just create a new project add a tabbed control, on tab 1 put a button on tab 2 put a check box (default names) and paste this code for its code public partial class Form1 : Form { private List<bool> boolList = new List<bool>(); BindingSource bs = new BindingSource(); public Form1() { InitializeComponent(); boolList.Add(false); bs.DataSource = boolList; checkBox1.DataBindings.Add("Checked", bs, ""); } bool updating = false; private void button1_Click(object sender, EventArgs e) { updating = true; boolList[0] = true; bs.ResetBindings(false); Application.DoEvents(); updating = false; } private void checkBox1_CheckedChanged(object sender, EventArgs e) { if (!updating) MessageBox.Show("CheckChanged fired outside of updating"); } } The issue is if you run the program and look at tab 2 then press the button on tab 1 the program works as expected, however if you press the button on tab 1 then look at tab 2 the event for the checkbox will not fire untill you look at tab 2. The reason for this is the controll on tab 2 is not in the "created" state, so its binding to change the checkbox from unchecked to checked does not happen until after the control has been "Created". checkbox1.CreateControl() does not do anything because according to MSDN CreateControl does not create a control handle if the control's Visible property is false. You can either call the CreateHandle method or access the Handle property to create the control's handle regardless of the control's visibility, but in this case, no window handles are created for the control's children. I tried getting the value of Handle(there is no CreateHandle for Button) but still the same result. Any suggestions other than have the program quickly flash all of my tabs that have data-bound check boxes when it first loads?

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• rails HABTM versus view (formtastic)

  - by VP

  I have two models: The model NetworkObject try to describe "hosts". I want to have a rule with source and destination, so i'm trying to use both objects from the same class since it dont makes sense to create two different classes. class NetworkObject < ActiveRecord::Base attr_accessible :ip, :netmask, :name has_many :statements has_many :rules, :through =>:statements end class Rule < ActiveRecord::Base attr_accessible :active, :destination_ids, :source_ids has_many :statements has_many :sources, :through=> :statements, :source=> :network_object has_many :destinations, :through => :statements, :source=> :network_object end To build the HABTM i did choose the Model JOIN. so in this case i created a model named Statement with: class Statement < ActiveRecord::Base attr_accessible :source_id, :rule_id, :destination_id belongs_to :network_object, :foreign_key => :source_id belongs_to :network_object, :foreign_key => :destination_id belongs_to :rule end The problem is: is right to add two belongs_to to the same class using different foreign_keys? I tried all combinations like: belongs_to :sources, :class_name => :network_object, :foreign_key => :source_id but no success.. anything that i am doing wrong?

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• Wanted to know in detail about how shared libraries work vis-a-vis static library.

  - by goldenmean

  Hello, I am working on creating and linking shared library (.so). While working with them, many questions popped up which i could not find satisying answers when i searched for them, hence putting them here. The questions about shared libraries i have are: 1.) How is shared library different than static library? What are the Key differences in way they are created, they execute? 2.) In case of a shared library at what point are the addresses where a particular function in shared library will be loaded and run from, given? Who gives those functions is load/run addresses? 3.) Will an application linked against shared library be slower in execution as compared to that which is linked with a static library? 4.) Will application executable size differ in these two cases? 5.) Can one do source level debugging of by stepping into functions defined inside a shared library? Is any thing extra needed to make these functions visible to the application? 6.) What are pros and cons in using either kind of library? Thanks. -AD

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• How to float a <div> echoed in the footer over a <div> located elsewhere (PHP/jQuery/HTML/CSS)

  - by PlasmaFlux

  Hello All! I'm embarking on a major project, but am stuck on a tiny issue at the very start. I'll try to be as concise as possible. I have a PHP script that will be echoing into the footer of the page (the last stuff before a bunch of s containing visible buttons and s containing hidden dialog boxes. The plan is to have the buttons float in the upper-right corner of corresponding s in the main content area of the page. i.e. - button-1 echoed into the footer will float in the corner of content-box-1, and will be tied to the hidden 'dialog-1'. I'll be using jQuery and jQuery UI Dialog throughout the page(s). I'm not sure if that's particularly relevant to this question, but thought it worth mentioning just in case. So my question, put simply, is how do I echo a Button 1 into the footer with PHP, but have it float in the upper-right corner (with maybe 5px margin) of Content 1 is full of content? A picture says a thousand words: As shown above, I want the little blue gear button things in the corner of content pieces, locked and loaded with hidden s containing dialog boxes. Again, the catch is that all buttons and hidden divs will be the very last items echoed into the page footer. I've found plenty of info on how to float divs on top of divs, but all the examples I saw showed the s in close proximity to each other in the page source; not with a hundred lines of source code between the two s I'm not sure if the solution is pure CSS, pure jQuery/jQueryUI or a combination of the two. Any advice will be much appreciated. Thanks!

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• Design suggestion for expression tree evaluation with time-series data

  - by Lirik

  I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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• PostgreSQL insert on primary key failing with contention, even at serializable level

  - by Steven Schlansker

  I'm trying to insert or update data in a PostgreSQL db. The simplest case is a key-value pairing (the actual data is more complicated, but this is the smallest clear example) When you set a value, I'd like it to insert if the key is not there, otherwise update. Sadly Postgres does not have an insert or update statement, so I have to emulate it myself. I've been working with the idea of basically SELECTing whether the key exists, and then running the appropriate INSERT or UPDATE. Now clearly this needs to be be in a transaction or all manner of bad things could happen. However, this is not working exactly how I'd like it to - I understand that there are limitations to serializable transactions, but I'm not sure how to work around this one. Here's the situation - ab: => set transaction isolation level serializable; a: => select count(1) from table where id=1; --> 0 b: => select count(1) from table where id=1; --> 0 a: => insert into table values(1); --> 1 b: => insert into table values(1); --> ERROR: duplicate key value violates unique constraint "serial_test_pkey" Now I would expect it to throw the usual "couldn't commit due to concurrent update" but I'm guessing since the inserts are different "rows" this does not happen. Is there an easy way to work around this?

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