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• c++ signatures, pointers

  - by coubeatczech

  Hello, what's the difference between these signatures? T * f(T & identifier); T & f(T & identifier); T f(T & identifier); void f(T * identifier); void f(T & identifier); void f(T identifier); I met pointers in c, but the amperstand in function signature is new for me. Can Anyone explain this?

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• How to improve the speed of a loop containing a sqlalchemy query statement as conditional

  - by LtPinback

  This loop checks if a record is in the sqlite database and builds a list of dictionaries for those records that are missing and then executes a multiple insert statement with the list. This works but it is very slow (at least i think it is slow) as it takes 5 minutes to loop over 3500 queries. I am a complete newbie in python, sqlite and sqlalchemy so I wonder if there is a faster way of doing this. list_dict = [] session = Session() for data in data_list: if session.query(Class_object).filter(Class_object.column_name_01 == data[2]).filter(Class_object.column_name_00 == an_id).count() == 0: list_dict.append({'column_name_00':a_id, 'column_name_01':data[2]}) conn = engine.connect() conn.execute(prices.insert(),list_dict) conn.close() session.close() edit: I moved session = Session() outside the loop. Did not make a difference.

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• Git: Make one branch exactly like another

  - by G. Martin

  I am relatively new to Git, and I'm still not very comfortable with it. Right now, I'm looking for the command/options/magic that can make the current branch look like another branch; that is, to merge them, but when a conflict arises, to always choose the difference in the branch that is being merged into the current one. My situation is thus; I have an stable(ish) application on the "master" branch. I also have another branch, called "feature". I basically want to make changes/additions/deletions to feature until I like the new feature I'm working on. Once I feel it is ready, I want to make the master branch look identical to the feature branch. I know this probably isn't a best practice, but as I said, I'm new to Git. I plan on learning how to do more complicated things in the future, but for now, this is all I need. Thanks, SO!

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• Does async and await incease performance of an ASP.Net application

  - by Kerezo

  I recently read a article about c#-5 and new $ nice asynchronous programming. I see it works greate in windows application. The question came to me before is if this feature can increase ASP.Net performance? consider this code: public T GetData() { var d = GetSomeData(); return d; } and public async T GetData2() { var d = await GetSomeData(); return d; } Has in an ASP.Net appication that two codes difference? thanks

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• C - memset segfault for statically allocated char array

  - by user1327031

  I get a segfault when trying to memset an array of chars that was allocated statically, but not for an array of the same length that was allocated using malloc. variable definitions: //static char inBuff[IN_BUFF_LEN]; //dynamic char * inBuffD; function call: //static, cast used because char** != char (*) [n] serverInit(portNum, (char**) &inBuff, &serv_addr, &sockfd) //dynamic serverInit(portNum, &inBuffD, &serv_addr, &sockfd) use within the function: memset(*inBuffAdr, 0, IN_BUFF_LEN); I suspect that my problem is in the difference of the function calls, or to be more precise, my incomplete understanding of the "char** != char (*) [n]" situation. But I have been banging at this for too long and can't see the forest from the trees so any hints and advice would be very appreciated.

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• Is there a way to intersect/diff a std::map and a std::set?

  - by Jack

  I'm wondering if there a way to intersect or make the differences between two structures defined as std::set<MyData*> and std::map<MyData*, MyValue> with standard algorithms (like std::set_intersect) The problem is that I need to compute the difference between the set and the keyset of the map but I would like to avoid reallocating it (since it's something that is done many times per second with large data structures). Is there a way to obtain a "key view" of the std::map? After all what I'm looking is to consider just the keys when doing the set operation so from an implementation point it should be possible but I haven't been able to find anything.

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• C++: need indexed set

  - by user231536

  I need an indexed associative container that operates as follows: initially empty, size=0. when I add a new element to it, it places it at index [size], very similar to a vector's push_back. It increments the size and returns the index of the newly added element. if the element already exists, it returns the index where it occurs. Set seems the ideal data structure for this but I don't see any thing like getting an index from a find operation. Find on a set returns an iterator to the element. Will taking the difference with set.begin() be the correct thing to do in this situation?

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• Can anyone tell why Wordpress is adding this p tag?

  - by Elliott Samuel Lemberger

  Here's the page: http://www.gammagoochee.com/media/ WP is adding a p tag on line 55 between the end of my header and the beginning of my post content. I am using Raw HTML Pro, and the post starts with content surrounded by [raw] tags. There is no content between the last tag in my header, and the beginning of my post. This doesn't happen on my other site pages, and the only difference is that this page is using a template, but the template is the same in this part of the page. All the template does differently than the other site pages is add a sidebar. Anyone have any ideas whatsoever why WP is adding this p tag, and/or how I can prevent it? Thanks so much!

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• Executing ffmpeg from php running in apache

  - by foobar

  I was executing ffmpeg from php running inside apache. I used to get the error " error while loading shared libraries: libavdevice.so.52: cannot open shared object file: No such file or directory". It used to work perfectly if the php script was executed from the command prompt or ffpmeg was directly invoked from the command prompt. I followed the below steps to fix the apache error: Step 1: Check if the file “libavdevice.so.52? exists in the server using the following command. find / -name ‘libavdevice.so.*’ Step 2: You will get the directory in which the file “libavdevice.so.52? exists from the above command. Suppose the directory is “/usr/local/lib/” in this example. Step 3: You have to add the directory name in the file “/etc/ld.so.conf”. Step 4: Execute the command “ldconfig”. How did doing the above make a difference to apache?

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• What is the role of `while`-loops in computation expressions in F#?

  - by MizardX

  If you define a While method of the builder-object, you can use while-loops in your computation expressions. The signature of the While method is: member b.While (predicate:unit->bool, body:M<'a>) : M<'a> For comparison, the signature of the For method is: member b.For (items:seq<'a>, body:unit->M<'a>) : M<'a> You should notice that, in the While-method, the body is a simple type, and not a function as in the For method. You can embed some other statements, like let and function-calls inside your computation-expressions, but those can impossibly execute in a while-loop more than once. builder { while foo() do printfn "step" yield bar() } Why is the while-loop not executed more than once, but merely repeated? Why the significant difference from for-loops? Better yet, is there some intended strategy for using while-loops in computation-expressions?

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• How to get available memory C++/g++ ?

  - by Agito

  I want to allocate my buffers according to memory available. Such that, when I do processing and memory usage goes up, but still remains in available memory limits. Is there a way to get available memory (I don't know will virtual or physical memory status will make any difference ?). And method has to be platform Independent as its going to be used on Windows, OS X, Linux and AIX. (And if possible then I would also like to allocate some of available memory for my application, someone it doesn't change during the execution).

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• C++ pointer to functions, Beginner Question...

  - by BobAlmond

  Hi all, I want to ask about pointer in C++ I have some simple code: int add(int a, int b){ return a+b; } int runner(int x,int y, int (*functocall)(int, int)){ return (*functocall)(x,y); } now, suppose I call those functions using this way : cout<<runner(2,5,&add); or maybe cout<<runner(2,5,add); is there any difference? because when I tried, the result is the same and with no error. Thanks a lot

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• How to get available memmory C++/g++ ?

  - by Agito

  I want to allocate my buffers according to memory available. Such that, when I do processing and memory usage goes up, but still remains in available memory limits. Is there a way to get available memory (I don't know will virtual or physical memory status will make any difference ?). And method has to be platform Independent as its going to be used on Windows, OS X, Linux and AIX. (And if possible then I would also like to allocate some of available memory for my application, someone it doesn't change during the execution).

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• Simple loop, which one I would get more performance and which one is recommended? defining a variable inside a loop or outside of it?

  - by Grego

  Variable outside of the loop int number = 0; for(int i = 0; i < 10000; i++){ number = 3 * i; printf("%d",number); } or Variable inside of the loop for(int i = 0; i < 10000; i++){ int number = 3 * i; printf("%d",number); } Which one is recommended and which one is better in performance? Edit: This is just an example to exhibit what I mean, All I wanna know is if defining a variable inside a loop and outside a loop means the same thing , or there's a difference.

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• receiving OPTIONS instead of GET requests?

  - by Urs

  Hi, all I want to achieve is to implement a servlet providing a json feed for my fullcalendar application. When I inspect http://arshaw.com/js/fullcalendar/examples/json.html with Bugzilla, I see that GET-requests are sent to receive the json feed. However, when I use this example within my scenario, fullcalendar seems to send OPTIONS-requests. The only difference is that I replaced "events: "json-events.php" with "http://localhost:8080/CalendarServletTest/HelloWorldServlet" (the url of my servlet). What do I miss? or is this really a bug?

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• Is there any memory restrictions on an ASP.Net application? HttpHandler?

  - by tpower

  I have an ASP.Net MVC application that allows users to upload images. When I try to upload a really large file (400MB) I get an error. I assumed that my image processing code (home brew) was very inefficient, so I decided I would try using a third party library to handle the image processing parts. Because I'm using TDD, I wanted to first write a test that fails. But when I test the controller action with the same large file it is able to do all the image processing without any trouble. The error I get is "Out of memory". I'm sure my code is probably using a lot more memory than it needs to but I just want to know why my test passes. The other difference is that I'm using SWFUpload which is not used with the test. Could this be the cause?

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• count(*) vs count(column-name) - which is more correct?

  - by bread

  Does it make a difference if you do count(*) vs count(column-name) as in these two examples? I have a tendency to always write count(*) because it seems to fit better in my mind with the notion of it being an aggregate function, if that makes sense. But I'm not sure if it's technically best as I tend to see example code written without the * more often than not. count(*): select customerid, count(*), sum(price) from items_ordered group by customerid having count(*) > 1; vs. count(column-name): SELECT customerid, count(customerid), sum(price) FROM items_ordered GROUP BY customerid HAVING count(customerid) > 1;

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• Performance implications of using a variable versus a magic number

  - by Nathan

  I'm often confused by this. I've always been taught to name numbers I use often using variables or constants, but if it reduces the efficiency of the program, should I still do it? Heres an example: private int CenterText(Font font, PrintPageEventArgs e, string text) { int recieptCenter = 125; int stringLength = Convert.ToInt32(e.Graphics.MeasureString(text, font)); return recieptCenter - stringLength / 2; } The above code is using named variables, but runs slower then this code: private int CenterText(Font font, PrintPageEventArgs e, string text) { return 125 - Convert.ToInt32(e.Graphics.MeasureString(text, font) / 2); } In this example, the difference in execution time is minimal, but what about in larger blocks of code?

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• Validation of viewstate MAC failed in Safari

  - by Midhat

  Hi I have a web app using forms authentication. When I perform the following steps Let the login cookie expire Click on a link that requires a logged in user The user is redirected to the login page Click the browser back button The user is redirected to the login page again Log in using a valid username/password I get this exception Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. This case appears only in safari (windows and mac). The fundamental difference between safari and other browsers is that when we click the back button in step 4, safari shows the login page again, while the other browsers show the previous page the user was working on. Please help in this regard

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• Are conditional subqueries optimized out, if the condition is false?

  - by Tobias Schulte

  I have a table foo and a table bar, where each foo might have a bar (and a bar might belong to multiple foos). Now I need to select all foos with a bar. My sql looks like this SELECT * FROM foo f WHERE [...] AND ($param IS NULL OR (SELECT ((COUNT(*))>0) FROM bar b WHERE f.bar = b.id)) with $param being replaced at runtime. The question is: Will the subquery be executed even if param is null, or will the dbms optimize the subquery out? We are using mysql, mssql and oracle. Is there a difference between these regarding the above?

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• What are the differences between struct and class in C++

  - by palm3D

  This question was already asked in the context of C#/.Net. Now I'd like to learn the differences between a struct and a class in (unmanaged) C++. Please discuss the technical differences as well as reasons for choosing one or the other in OO design. I'll start with an obvious difference: If you don't specify public: or private:, members of a struct are public by default; members of a class are private by default. I'm sure there are other differences to be found in the obscure corners of the C++ specification.

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• DocumentBuilder.parse() / Parsing Entities

  - by stormin986

  I'm new to parsing XML and am having an issue with entities. (Am doing this on Android, if it makes a difference). Is there a way to have it turn an entity into the character it represents? I have this in the child of an element: "isn&#39;t" (minus quotes). I would prefer it parse it and the end result be a single text node. However, right now this is turned in to TEXT, ENTITY, TEXT. Is there a way to automatically have it parse the entity into text, or a manual way to do it?

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• How the websocket bi-directional concept work?

  - by GMsoF

  I think the main difference between websocket and http streaming (I am not refering to polling and long polling) is websocket allows bi-directional communication which is similar to usual raw socket programming. (above is my understanding, could be wrong, feel free to correct me.) My question is how the web client (browser) continue to send another request in the already-opened websocket? Usual http request will treat another request as new socket connection, but websocket does not, that is why I am confused, how it achieve that? It should be handled in Server side or Client (browser) side?

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• Are these 2 sql queries equivalent in all respects (e.g. estimated and actual execution plan)?

  - by Xerion

  Are query 1) == 2) in terms of estimated query plan AND actual plan? (can statistics affect the actual plan here, ever?) declare @cat int -- input param from prc ... 1) select * from A as a join B as b on b.id = a.id on b.cat = @cat join C as c on c.fid = b.fid on c.cat = @cat where a.cat = @cat 2) select * from A as a join B as b on b.id = a.id on b.cat = a.cat join C as c on c.fid = b.fid on c.cat = b.cat where a.cat = @cat It seems to me that these should logically be equivalent and the execution plan should always be the same regardless of actual difference in tables. And adding more conditions either in join, or where, or add more tables to join shouldn't change this. Are there cases this is not true?

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• Game network physics collision

  - by Jonas Byström

  How to simulating two client-controlled vehicles colliding (sensibly) in a typical client/server setup for a network game? I did read this eminent blog post on how to do distributed network physics in general (without traditional client prediction), but this question is specifically on how to handle collisions of owned objects. Example Say client A is 20 ms ahead of server, client B 300 ms ahead of server (counting both latency and maximum jitter). This means that when the two vehicles collide, both clients will see the other as 320 ms behind - in the opposite direction of the velocity of the other vehicle. Head-to-head on a Swedish highway means a difference of 16 meters/17.5 yards! What not to try It is virtually impossible to extrapolate the positions, since I also have very complex vehicles with joints and bodies all over, which in turn have linear and angular positions, velocities and accelerations, not to mention states from user input.

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