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• Google app engine: Poor Performance with JDO + Datastore

  - by Bosh

  I have a simple data model that includes USERS: store basic information (key, name, phone # etc) RELATIONS: describe, e.g. a friendship between two users (supplying a relationship_type + two user keys) I'm getting very poor performance, for instance, if I try to print the first names of all of a user's friends. Say the user has 500 friends: I can fetch the list of friend user_ids very easily in a single query. But then, to pull out first names, I have to do 500 back-and-forth trips to the Datastore, each of which seems to take on the order of 30 ms. If this were SQL, I'd just do a JOIN and get the answer out fast. I understand there are rudimentary facilities for performing joins across un-owned relations in a relaxed implementation of JDO (as described at http://gae-java-persistence.blogspot.com) but they sound experimental and non-standard (e.g. my code won't work in any other JDO implementation). Is this really my best bet? Otherwise, how do people extract satisfactory performance from JDO/Datastore in this kind of (very common) situation? -Bosh

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• How do I ensure a Flex dataProvider processes the data synchronously?

  - by Matt Calthrop

  I am using an component, and currently have a dataProvider working that is an ArrayCollection (have a separate question about how to make this an XML file... but I digress). Variable declaration looks like this: [Bindable] private var _dpImageList : ArrayCollection = new ArrayCollection([ {"location" : "path/to/image1.jpg"}, {"location" : "path/to/image2.jpg"}, {"location" : "path/to/image3.jpg"} ]); I then refer to like this: <s:List id="lstImages" width="100%" dataProvider="{_dpImageList}" itemRenderer="path.to.render.ImageRenderer" skinClass="path.to.skins.ListSkin" > <s:layout> <s:HorizontalLayout gap="2" /> </s:layout> </s:List> Currently, it would appear that each item is processed asynchronously. However, I want them to be processed synchronously. Reason: I am displaying a list of images, and I want the leftmost one rendered first, followed by the one to its right, and so on. Edit: I just found this answer. Do you think that could be the same issue?

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• Compact data structure for storing a large set of integral values

  - by Odrade

  I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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• How to write a flexible modular program with good interaction possibilities between modules?

  - by PeterK

  I went through answers on similar topics here on SO but could't find a satisfying answer. Since i know this is a rather large topic, i will try to be more specific. I want to write a program which processes files. The processing is nontrivial, so the best way is to split different phases into standalone modules which then would be used as necessary (since sometimes i will be only interested in the output of module A, sometimes i would need output of five other modules, etc). The thing is, that i need the modules to cooperate, because the output of one might be the input of another. And i need it to be FAST. Moreover i want to avoid doing certain processing more than once (if module A creates some data which then need to be processed by module B and C, i don't want to run module A twice to create the input for modules B,C ). The information the modules need to share would mostly be blocks of binary data and/or offsets into the processed files. The task of the main program would be quite simple - just parse arguments, run required modules (and perhaps give some output, or should this be the task of the modules?). I don't need the modules to be loaded at runtime. It's perfectly fine to have libs with a .h file and recompile the program every time there is a new module or some module is updated. The idea of modules is here mainly because of code readability, maintaining and to be able to have more people working on different modules without the need to have some predefined interface or whatever (on the other hand, some "guidelines" on how to write the modules would be probably required, i know that). We can assume that the file processing is a read-only operation, the original file is not changed. Could someone point me in a good direction on how to do this in C++ ? Any advice is wellcome (links, tutorials, pdf books...).

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• Possibility of a custom Contacts field with a set list of values and Contacts lookup performance

  - by areyling

  I'm pretty sure it's not viable to do what I'd like to based on some initial research, but I figured it couldn't hurt to ask the community of experts here in case someone knows a way. I'd like to create a custom field for contacts that the user is able to edit from the main Contacts app; however, the user should only be allowed to select from a list of four specific values. A short list of string values would be ideal, but an int with a min/max range would suffice. I'm interested in knowing if it's possible either way, but also wondering if it make sense to go this route performance wise. More specifically, would it be better to look up a contact (based on a phone number) each time a call or SMS message is received or better to store my own set of data (consisting of name, numbers, and the custom field) and just syncing contact info in a thread every so often? Or syncing contacts the first time the app is run and then registering for changes using ContentObserver? Here is a similar question with an answer that explains how to add a custom field to a contact. Thanks in advance.

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• Script to install and compile Python, Django, Virtualenv, Mercurial, Git, LessCSS, etc... on Dreamho

  - by tmslnz

  The Story After cleaning up my Dreamhost shared server's home folder from all the cruft accumulated over time, I decided to start afresh and compile/reinstall Python. All tutorials and snippets I found seemed overly simplistic, assuming (or ignoring) a bunch of dependencies needed by Python to compile all modules correctly. So, starting from http://andrew.io/weblog/2010/02/installing-python-2-6-virtualenv-and-virtualenvwrapper-on-dreamhost/ (so far the best guide I found), I decided to write a set-and-forget Bash script to automate this painful process, including along the way a bunch of other things I am planning to use. The Script I am hosting the script on http://bitbucket.org/tmslnz/python-dreamhost-batch/src/ The TODOs So far it runs fine, and does all it needs to do in about 900 seconds, giving me at the end of the process a fully functional Python / Mercurial / etc... setup without even needing to log out and back in. I though this might be of use for others too, but there are a few things that I think it's missing and I am not quite sure how to go for it, what's the best way to do it, or if this just doesn't make any sense at all. Check for errors and break Check for minor version bumps of the packages and give warnings Check for known dependencies Use arguments to install only some of the packages instead of commenting out lines Organise the code in a manner that's easy to update Optionally make the installers and compiling silent, with error logging to file failproof .bashrc modification to prevent breaking ssh logins and having to log back via FTP to fix it EDIT: The implied question is: can anyone, more bashful than me, offer general advice on the worthiness of the above points or highlight any problems they see with this approach? (see my answer to Ry4an's comment below) The Gist I am no UNIX or Bash or compiler expert, and this has been built iteratively, by trial and error. It is somehow going towards apt-get (well, 1% of it...), but since Dreamhost and others obviously cannot give root access on shared servers, this looks to me like a potentially very useful workaround; particularly so with some community work involved.

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• scanf a byte then print it out?

  - by Sarah

  I've searched around to see if I can find this answer but I can't seem to (please let me know if I'm wrong). I am trying to use scanf to read in a byte, an unsigned int and a char in one .c file and I am trying to access this byte in a different .c file and print it out. (I have already checked to make sure I have included all the appropriate parameters everywhere) But I keep getting errors. The warnings are: database.c: In function ‘addCitizen’: database.c:23:2: warning: format ‘%hhu’ expects argument of type ‘int’, but argument 2 has type ‘byte *’ [-Wformat] database.c:24:2: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 2 has type ‘int *’ [-Wformat] database.c:25:2: warning: format ‘%c’ expects argument of type ‘int’, but argument 2 has type ‘char *’ [-Wformat] where I'm scanf'ing: // Request loop while (count-- != 0) { while (1){ // Get values from the user int error = scanf ("%79s %hhu %u %c", tname, &tdist, &tyear, &tgender); addCitizen(db, tname, &tdist, &tyear, &tgender); where I'm printing: void addCitizen(Database *db, char *tname, byte *tdist, int *tyear, char *tgender){ //needs to find the right place in memory to put this stuff and then put it there printf("\nName is: %79s\n", tname); printf("District is: %hhu\n", tdist); printf("Year of birth is: %u\n", tyear); printf("Gender is:%c\n", tgender); I'm not sure where I'm going wrong?

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• Why does Android allocate more memory than needed when loading images

  - by Simon

  Folks, I don't think that this is a duplicate and is NOT one of those how do I avoid OOMs questions. This is a genuine quest for knowledge so hold off on those down votes please... Imagine I have a JPEG of 500x500 pixels. I load it as ARGB_8888 which is as "bad as it gets". I would expect Android to allocate 500x500x4 bytes = a little under 1MB however, look at a heap dump and you will see that Android allocates significantly more, often factors of 5-10 times greater. You frequently see questions on here about OOMS where the stack trace shows a heap request of say 15MB and it is ALWAYS much larger than is required simply to hold the bytes of the image. The OP usually catches some downvotes then is bombarded with stock answers and comments about using less memory (thanks Romain!) and in scaling. I think there is more than meets the eye here. Anybody know why this is? If there is no apparent answer, I will put together an SSCCE if it helps. PS. I assume that JPEG vs PNG etc is irrelevant since we're talking about the memory usage of the backing bitmap which is simply x times y times BPP - or am I being slow?

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• Project Euler, Problem 10 java solution not working

  - by Dennis S

  Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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• What are the differences between mapping,binding and parsing?

  - by sfrj

  I am starting to learn web-services in java EE6. I did web development before, but never nothing related to web services. All is new to me and the books and the tutorials i find in the web are to technical. I started learning about .xsd schemas and also .xml. In that topic i feel confident, i understand what are the schemas used for and what validation means. Now my next step is learning about JAX-B(Java Api for XML Binding). I rode some about it and i did also some practice in my IDE. But i have lots of basic doubts, that make me stuck and cannot feel confident to continue to the next topic. Ill appreciate a lot if someone could explain me well my doubts: What does it mean mapping and what is a mapping tool? What does it mean binding and what is a binding tool? What does it mean parsing and what is a parsing tool? How is JAX-B related to mapping,binding and parsing? I am seeking for a good answer built by you, not just a copy paste from google(Ive already been online a few hours and only got confused).

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• Expanding DIV slides behind DIV beneath it...

  - by Paddy

  I'm not sure that I'm going to get an answer here, as I'd need to post a lot of CSS and html to get a working recreation, however... I have structure something like this: <fieldset> <legend>Test A</legend> <h3>Test A</h3> <p> Something here. </p> <div style="display:hidden;">I'm dynamically displayed</div> </fieldset> <fieldset> <legend>Test B</legend> <h3>Test B</h3> <p> Something B here. </p> </fieldset> I have code that toggles the display of my hidden div using jQuery and .show(). This works fine in IE8, firefox and Safari, but when I stick IE8 into compatibility mode, then the first fieldset (Test A) will expand, but the expansion happens behind the second fieldset, which doesn't move (i.e. it slides down behind it). I have quite a bit of CSS in use here, and I'm going to have to go back and unpick the whold lot, which isn't a fun idea. If anybody has any idea of one of the IE7 rendering issues that might be affecting this, then I'd very much appreciate it. (note that there is more to the content in these fieldsets than shown, including floated divs). Quick note - if I stick IE7 into quirks mode, it works (but wrecks the rest of my layout) - in standards mode, I get the above behaviour.

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• C# Virtual method call in constructor - how to refactor?

  - by Cristi Diaconescu

  I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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• Pairs from single list

  - by Apalala

  Often enough, I've found the need to process a list by pairs. I was wondering which would be the pythonic and efficient way to do it, and found this on Google: pairs = zip(t[::2], t[1::2]) I thought that was pythonic enough, but after a recent discussion involving idioms versus efficiency, I decided to do some tests: import time from itertools import islice, izip def pairs_1(t): return zip(t[::2], t[1::2]) def pairs_2(t): return izip(t[::2], t[1::2]) def pairs_3(t): return izip(islice(t,None,None,2), islice(t,1,None,2)) A = range(10000) B = xrange(len(A)) def pairs_4(t): # ignore value of t! t = B return izip(islice(t,None,None,2), islice(t,1,None,2)) for f in pairs_1, pairs_2, pairs_3, pairs_4: # time the pairing s = time.time() for i in range(1000): p = f(A) t1 = time.time() - s # time using the pairs s = time.time() for i in range(1000): p = f(A) for a, b in p: pass t2 = time.time() - s print t1, t2, t2-t1 These were the results on my computer: 1.48668909073 2.63187503815 1.14518594742 0.105381965637 1.35109519958 1.24571323395 0.00257992744446 1.46182489395 1.45924496651 0.00251388549805 1.70076990128 1.69825601578 If I'm interpreting them correctly, that should mean that the implementation of lists, list indexing, and list slicing in Python is very efficient. It's a result both comforting and unexpected. Is there another, "better" way of traversing a list in pairs? Note that if the list has an odd number of elements then the last one will not be in any of the pairs. Which would be the right way to ensure that all elements are included? I added these two suggestions from the answers to the tests: def pairwise(t): it = iter(t) return izip(it, it) def chunkwise(t, size=2): it = iter(t) return izip(*[it]*size) These are the results: 0.00159502029419 1.25745987892 1.25586485863 0.00222492218018 1.23795199394 1.23572707176 Results so far Most pythonic and very efficient: pairs = izip(t[::2], t[1::2]) Most efficient and very pythonic: pairs = izip(*[iter(t)]*2) It took me a moment to grok that the first answer uses two iterators while the second uses a single one. To deal with sequences with an odd number of elements, the suggestion has been to augment the original sequence adding one element (None) that gets paired with the previous last element, something that can be achieved with itertools.izip_longest().

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• Assign Multiple Custom User Roles to a Custom Post Type

  - by OUHSD Webmaster

  Okay here's the situation.... I'm working on a my business website. There will be a work/portfolio area. "Work" is a custom post type. "Designer" is a custom user role. "Client" is a custom user role. In creating a new "Work" post I would like to be able to select both a "designer" and "Client" to assign to the piece of work, as I would assign an author to a regular ol' post. I tried the method from this answer but it did not work for me. ) I placed it in my functions.php file. ` add_filter('wp_dropdown_users', 'test'); function test($output) { global $post; //Doing it only for the custom post type if($post->post_type == 'work') { $users = get_users(array('role'=>'designer')); //We're forming a new select with our values, you can add an option //with value 1, and text as 'admin' if you want the admin to be listed as well, //optionally you can use a simple string replace trick to insert your options, //if you don't want to override the defaults $output .= "<select id='post_author_override' name='post_author_override' class=''>"; foreach($users as $user) { $output .= "<option value='".$user->id."'>".$user->user_login."</option>"; } $output .= "</select>"; } return $output; } ` Any help would be extremely appreciated!

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• How to implement generic callbacks in C++

  - by Kylotan

  Forgive my ignorance in asking this basic question but I've become so used to using Python where this sort of thing is trivial that I've completely forgotten how I would attempt this in C++. I want to be able to pass a callback to a function that performs a slow process in the background, and have it called later when the process is complete. This callback could be a free function, a static function, or a member function. I'd also like to be able to inject some arbitrary arguments in there for context. (ie. Implementing a very poor man's coroutine, in a way.) On top of that, this function will always take a std::string, which is the output of the process. I don't mind if the position of this argument in the final callback parameter list is fixed. I get the feeling that the answer will involve boost::bind and boost::function but I can't work out the precise invocations that would be necessary in order to create arbitrary callables (while currying them to just take a single string), store them in the background process, and invoke the callable correctly with the string parameter.

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• How to implement a 'safe' periodical executer without using the Rails helpers?

  - by Robbie

  I am very new to Ruby on Rails and was never really big on writing JavaScript, so the built in helpers were like a tiny silce of heaven. However I have recently learned that using the helper methods creates "obtrusive javascript" so I am doing a tiny bit of refactoring to get all this messy code out of my view. I'm also using the Prototype API to figure out what all these functions do. Right now, I have: <%= periodically_call_remote(:url => {:action => "tablerefresh", :id => 1 }, :frequency => '5', :complete => "load('26', 'table1', request.responseText)")%> Which produces: <script type="text/javascript"> //<![CDATA[ new PeriodicalExecuter(function() {new Ajax.Request('/qrpsdrail/grids/tablerefresh/1', {asynchronous:true, evalScripts:true, onComplete:function(request){load('26', 'table1', request.responseText)}, parameters:'authenticity_token=' + encodeURIComponent('dfG7wWyVYEpelfdZvBWk7MlhzZoK7VvtT/HDi3w7gPM=')})}, 5) //]]> </script> My concern is that the "encodeURIComponent" and the presence of "authenticity_token" are generated by Rails. I'm assuming these are used to assure the validity of a request. (Ensuring a request comes from a currently active session?) If that is the case, how can I implement this in application.js 'safely'? It seems that the built in method, although obtrusive, does add some beneficial security. Thanks, in advance, to all who answer.

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• .NET Regex - Replace multiple characters at once without overwriting?

  - by Everaldo Aguiar

  I'm implementing a c# program that should automatize a Mono-alphabetic substitution cipher. The functionality i'm working on at the moment is the simplest one: The user will provide a plain text and a cipher alphabet, for example: Plain text(input): THIS IS A TEST Cipher alphabet: A - Y, H - Z, I - K, S - L, E - J, T - Q Cipher Text(output): QZKL KL QJLQ I thought of using regular expressions since I've been programming in perl for a while, but I'm encountering some problems on c#. First I would like to know if someone would have a suggestion for a regular expression that would replace all occurrence of each letter by its corresponding cipher letter (provided by user) at once and without overwriting anything. Example: In this case, user provides plaintext "TEST", and on his cipher alphabet, he wishes to have all his T's replaced with E's, E's replaced with Y and S replaced with J. My first thought was to substitute each occurrence of a letter with an individual character and then replace that character by the cipherletter corresponding to the plaintext letter provided. Using the same example word "TEST", the steps taken by the program to provide an answer would be: 1 - replace T's with (lets say) @ 2 - replace E's with # 3 - replace S's with & 4 - Replace @ with E, # with Y, & with j 5 - Output = EYJE This solution doesn't seem to work for large texts. I would like to know if anyone can think of a single regular expression that would allow me to replace each letter in a given text by its corresponding letter in a 26-letter cipher alphabet without the need of splitting the task in an intermediate step as I mentioned. If it helps visualize the process, this is a print screen of my GUI for the program:

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• How do I know which Object I clicked?

  - by Nick

  Here's the deal: I'm working on a personal portfolio in AS3 and I've run into a problem which I can't seem to find a logical answer to. I want everything (well, most of it) to be editable with an XML file, including my menu. My menu is just a Sprite with some text on it and a Tweener-tween, no big deal. But, I forgot to think of a way how I can determine which menu-item I have clicked. This is in my Main.as private function xmlLoaded(e:Event):void { xml = e.target.xml; menu = new Menu(xml); menu.x = 0; menu.y = stage.stageHeight / 2 - menu.height / 2; addChild(menu); } In Menu.as public function Menu(xml:XML) { for each (var eachMenuItem:XML in xml.menu.item) { menuItem = new MenuItem(eachMenuItem); menuItem.y += yPos; addChild(menuItem); yPos += menuItem.height + 3; } } and in my MenuItem.as, everything works - I have a fancy tween when I hover over it, but when I click a menu-item, I want something to appear ofcourse. How do I know which one I clicked? I've tried with pushing everything in an array, but that didn't work out well (or maybe I'm doing it wrong). Also tried a global counter, but that's not working either because the value will always be amount of items in my XML file. Also tried e.currentTarget in my click-function, but when I trace that, all of them are "Object Sprite".. I need something so I can give each a unique "name"? Thanks in advance!

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• What is happening in this T-SQL code? (Concatenting the results of a SELECT statement)

  - by Ben McCormack

  I'm just starting to learn T-SQL and could use some help in understanding what's going on in a particular block of code. I modified some code in an answer I received in a previous question, and here is the code in question: DECLARE @column_list AS varchar(max) SELECT @column_list = COALESCE(@column_list, ',') + 'SUM(Case When Sku2=' + CONVERT(varchar, Sku2) + ' Then Quantity Else 0 End) As [' + CONVERT(varchar, Sku2) + ' - ' + Convert(varchar,Description) +'],' FROM OrderDetailDeliveryReview Inner Join InvMast on SKU2 = SKU and LocationTypeID=4 GROUP BY Sku2 , Description ORDER BY Sku2 Set @column_list = Left(@column_list,Len(@column_list)-1) Select @column_list ---------------------------------------- 1 row is returned: ,SUM(Case When Sku2=157 Then Quantity Else 0 End) As [157 -..., SUM(Case ... The T-SQL code does exactly what I want, which is to make a single result based on the results of a query, which will then be used in another query. However, I can't figure out how the SELECT @column_list =... statement is putting multiple values into a single string of characters by being inside a SELECT statement. Without the assignment to @column_list, the SELECT statement would simply return multiple rows. How is it that by having the variable within the SELECT statement that the results get "flattened" down into one value? How should I read this T-SQL to properly understand what's going on?

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• Writing a VM - well formed bytecode?

  - by David Titarenco

  Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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• SWIG interface to receive an opaque struct reference in Java through function argument

  - by Beeo

  I am trying to use SWIG in order to use the Spotify API (libspotify) for Android: https://developer.spotify.com/technologies/libspotify/ I am having trouble defining the SWIG interface file to be able to successfully call the following native C function: sp_error sp_session_create(const sp_session_config * config, sp_session ** sess); Which in C would be called like this: //config struct defined previously sp_session *sess; sp_session_create(&config, &sess); But in Java I would need to call it like this: //config object defined previously sp_session javaSess = new sp_session(); sp_session_create(config, javaSess); sp_session is an opaque struct and is only defined in libspotify's API.h file as: typedef struct sp_session sp_session; I'm expecting the libspotify library to create it and give me a reference to it. The only thing I need that reference for then is to pass to other functions in the API. I believe the answer lies within the SWIG interface and typemaps, but I have been unsuccessful in trying to apply the examples I found in the documentation: http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_struct_pointer_pointer `http://www.swig.org/Doc2.0/SWIGDocumentation.html#Java_using_typemaps_return_arguments Help!

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• GlassFish 3: how do you change the (default) logging format?

  - by Kawu

  The question originated from here: http://www.java.net/forum/topic/glassfish/glassfish/configuring-glassfish-logging-format - without an answer. The default GlassFish 3 logging format of is very annoying, much too long. [#|2012-03-02T09:22:03.165+0100|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=113;_ThreadName=AWT-EventQueue-0;| MESSAGE... ] This is just a horrible default IMO. The docs just explain all the fields, but not how to change the format: http://docs.oracle.com/cd/E18930_01/html/821-2416/abluk.html Note, that I deploy SLF4J along with my webapp which should pick up the format as well. How do you change the logging format? FYI: The links here are outdated: Install log formater in glassfish... The question here hasn't been answered: How to configure GlassFish logging to show milliseconds in timestamps?... The posting here resulted in nothing: http://www.java.net/forum/topic/glassfish/glassfish/cant-seem-configure-... It looks like GlassFish logging configuration is an issue of its own. Can anybody help?

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• WPF ContextMenu bind some property to another property of the same control

  - by bebicasoft

  I have a ContextMenu and a ColumnHeaderStyle defined in Window.Resource section witch i use-it to a DataGrid ColumnHeader. My code is something like this: <ContextMenu x:Key="cm_columnHeaderMenu"/> <Style x:Key="DefaultColumnHeaderStyle" TargetType="{x:Type DataGridColumnHeader}"> <Setter Property="ContextMenu" Value="{StaticResource cm_columnHeaderMenu}" /> </Style> <DataGrid Grid.Column="2" Grid.Row="1" x:Name="dgridFiles" IsReadOnly="True" ColumnHeaderStyle="{StaticResource DefaultColumnHeaderStyle}"> I want to know if I can (and if the answer it true, then HOW I could do it) bind the ContextMenu Visibility property to same control ContextMenu Items.Count>0 property. Initially based on some other treeView control selections made there shoud be no items in the context menu, but i wish to add dinamically items in ContextMenu based on selection in treeView. This part is done, the context has those items. On some selections there are no-items, but still on the grid it appears an empty ContextMenu. So I believe the easiest part it would be to bind the Visibility to Items.Count property of the same control. Sorry if my english is not good enought, I'll try to explain better if i didnt make clear 1st time.

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• IF-block brackets: best practice

  - by MasterPeter

  I am preparing a short tutorial for level 1 uni students learning JavaScript basics. The task is to validate a phone number. The number must not contain non-digits and must be 14 digits long or less. The following code excerpt is what I came up with and I would like to make it as readable as possible. if ( //set of rules for invalid phone number phoneNumber.length == 0 //empty || phoneNumber.length > 14 //too long || /\D/.test(phoneNumber) //contains non-digits ) { setMessageText(invalid); } else { setMessageText(valid); } A simple question I can not quite answer myself and would like to hear your opinions on: How to position the surrounding (outermost) brackets? It's hard to see the difference between a normal and a curly bracket. Do you usually put the last ) on the same line as the last condition? Do you keep the first opening ( on a line by itself? Do you wrap each individual sub-condition in brackets too? Do you align horizontally the first ( with the last ), or do you place the last ) in the same column as the if? Do you keep ) { on a separate line or you place the last ) on the same line with the last sub-condition and then place the opening { on a new line? Or do you just put the ) { on the same line as the last sub-condition? Community wiki.

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• Can't get KnownType to work with WCF

  - by Kelly Cline

  I have an interface and a class defined in separate assemblies, like this: namespace DataInterfaces { public interface IPerson { string Name { get; set; } } } namespace DataObjects { [DataContract] [KnownType( typeof( IPerson ) ) ] public class Person : IPerson { [DataMember] public string Name { get; set; } } } This is my Service Interface: public interface ICalculator { [OperationContract] IPerson GetPerson ( ); } When I update my Service Reference for my Client, I get this in the Reference.cs: public object GetPerson() { return base.Channel.GetPerson(); I was hoping that KnownType would give me IPerson instead of "object" here. I have also tried [KnownType( typeof( Person ) ) ] with the same result. I have control of both client and server, so I have my DataObjects (where Person is defined) and DataInterfaces (where IPerson is defined) assemblies in both places. Is there something obvious I am missing? I thought KnownType was the answer to being able to use interfaces with WCF. ----- FURTHER INFORMATION ----- I removed the KnownType from the Person class and added [ServiceKnownType( typeof( Person ) ) ] to my service interface, as suggested by Richard. The client-side proxy still looks the same, public object GetPerson() { return base.Channel.GetPerson(); , but now it doesn't blow up. The client just has an "object", though, so it has to cast it to IPerson before it is useful. var person = client.GetPerson ( ); Console.WriteLine ( ( ( IPerson ) person ).Name );

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