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• How to link pnglite library in c?

  - by zaplec

  Hi, I installed from kubuntu's package management this handy pnglite library. It contains just one header file "pnglite.h" and one object file "pnglite.o". I have found out where those files are, but I don't know how to link them. I'm using netbeans, but don't know how to link them in there. Also I don't understand how to link them at console. I have a little test program that I would like to test, but I get the error message "undefined reference to function: XXXXXXX". Both netbeans and at console I'm using gcc. That header file is in /usr/include directory, object file is in /usr/lib directory and my test program is under my programming directory at my home directory. Should I put that header and object into the same directory as where my source is? Or is there a way to link them from their current locations? I know that it should be possible to link them from where they are at the moment and I would like to know and understand how to do that. Any help will be appreciated :)

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• Simulated Annealing and Yahtzee!

  - by Jasie

  I've picked up Programming Challenges and found a Yahtzee! problem which I will simplify: There are 13 scoring categories There are 13 rolls by a player (comprising a play) Each roll must fit in a distinct category The goal is to find the maximum score for a play (the optimal placement of rolls in categories); score(play) returns the score for a play Brute-forcing to find the maximum play score requires 13! (= 6,227,020,800) score() calls. I choose simulated annealing to find something close to the highest score, faster. Though not deterministic, it's good enough. I have a list of 13 rolls of 5 die, like: ((1,2,3,4,5) #1 (1,2,6,3,4),#2 ... (1,4,3,2,2) #13 ) And a play (1,5,6,7,2,3,4,8,9,10,13,12,11) passed into score() returns a score for that play's permutation. How do I choose a good "neighboring state"? For random-restart, I can simply choose a random permutation of nos. 1-13, put them in a vector, and score them. In the traveling salesman problem, here's an example of a good neighboring state: "The neighbours of some particular permutation are the permutations that are produced for example by interchanging a pair of adjacent cities." I have a bad feeling about simply swapping two random vector positions, like so: (1,5,6,7, 2 , 3,4,8,9,10, 13, 12,11) # switch 2 and 13 (1,5,6,7, 13, 3,4,8,9,10, 2 , 12,11) # now score this one But I have no evidence and don't know how to select a good neighboring state. Anyone have any ideas on how to pick good neighboring states?

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• How can i get rid of 0xFEEFEE in VC

  - by egebilmuh

  Hi guys I m programming C for an assingment in VC++ 2008. I simulate adjList for graph implementation. i can readly add edge between two vertex and print the graph. and i want to remove edge between two vertex and print the graph again. whatever i do,i cant print the graph after deleting the edge. i get 0xfeefee :( what is this? and how can i resolve this program. my delete function and print the graph function are illustrated below. void deleteEdge(Graph G, Vertex V, Vertex W) { Edge list,prev,temp; list=V->list; prev=NULL; // while(list!=NULL && list->to->value!=W->value){ prev=list; list=list->next; } // have found the element. if(list!=NULL){ temp=list; // if first element of list is deleted. if(prev==NULL) list=list->next; else prev->next=list->next; // reallocate. free(temp); } } void GRAPHprint(Graph G) { Vertex tmp; Edge list; for(tmp = G->head;tmp!=NULL;tmp=tmp->next) { fprintf(stdout,"V:%d\t",tmp->value); list=tmp->list; while(list!=NULL) { fprintf(stdout,"%d\t",list->to->value); list=list->next; } fprintf(stdout, "\n"); } system("pause"); }

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• How do the size standard libraries compare for different languages

  - by Roman A. Taycher

  Someone was recently raving about how great jQuery was and how it made javascript into a pleasure and also how the whole source code was so small(and one file). I looked it up on www.ohloh.net/ and it said it was about 30,000 lines of javascript, when I tired curl piped to wc it said about 5000 lines(strange discrepancy that, maybe test suites, ect?). I thought well it isn't that strange since javascript from what I've heard has a lot of fun dynamic tricks, so you can probably get away with a small library. But then I thought what about other high level languages, the ones with large standard libraries and wondered how big the standard are for python/ruby/haskell/pharo(smalltalk)/*ml/ect. (libraries not vm stuff to the degree its possible to separate it) Anybody know? Any details (comment/blank/code lines , test code lines, lines in language vs lines in ffi/byte-code) are appreciated! edit: ps. since it started this me asking about jQuery as a bonus if you could please list the size of mega frameworks, a megaframewok provides so much that people using an x megaframework in language y might sometimes refer to programming in xy or even x rather then in y (ie. : qt, jQuery, etc.).

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• How to debug PHP?

  - by NutMotion

  Anyone's been trying himself at object oriented programming ? Most probably every developer I guess:D I for one have never studied OO design patterns thoroughly, and trying to put it all together now does prove at times thrilling, and many times frustrating also. Even more so when trying to do it in : PHP! All-in-all, my boss asked me to add some Database persistence functions to her server, but most of all, she asked me to translate her already working procedural code into a working Object Oriented code. Here I am, still standing on my PHP OO project. I'm (already) fed up with this "file logging only" PHP capability. I believe there must be some (free or not too much expansive) PHP debugging utility ? I've heard about Zend Studio and PHPEd so far, which didn't quite do the trick for whatever reasons. WIRCW("Which I don't Remember Correctly Why" lol) What say yé? on debugging PHP ? Is there a tool that provides a good debug mode? what's more, don't forget I'm not speaking about the classical web Request/response model. Talking about a debugging facility which can enable you to trigger a web service (aka client request) and go into debug mode on the SOAP web service side. Thks for any input.

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• Given 4 objects, how to figure out whether exactly 2 have a certain property

  - by Cocorico

  Hi guys! I have another question on how to make most elegant solution to this problem, since I cannot afford to go to computer school right so my actual "pure programming" CS knowledge is not perfect or great. This is basically an algorhythm problem (someone please correct me if I am using that wrong, since I don't want to keep saying them and embarass myself) I have 4 objects. Each of them has an species property that can either be a dog, cat, pig or monkey. So a sample situation could be: object1.species=pig object2.species=cat object3.species=pig object4.species=dog Now, if I want to figure out if all 4 are the same species, I know I could just say: if ( (object1.species==object2.species) && (object2.species==object3.species) && (object3.species==object4.species) ) { // They are all the same animal (don't care WHICH animal they are) } But that isn't so elegant right? And if I suddenly want to know if EXACTLY 3 or 2 of them are the same species (don't care WHICH species it is though), suddenly I'm in spaghetti code. I am using Objective C although I don't know if that matters really, since the most elegant solution to this is I assume the same in all languages conceptually? Anyone got good idea? Thanks!!

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• Unable to ping server from client B but able to ping from client A. Please help

  - by Soundar Rajan

  This is not really a programming question, but I am at my wit's end ... I am trying to configure a IIS 6.0/Windows Server 2003 web server with a ASP.net application. When I try to ping the server from client computer A I get the following: PING 74.208.192.xxx ==> Ping fails PING 74.208.192.xxx:80 ==> Ping succeeds! From client computer B, BOTH the pings fail. PING 74.208.192.xxx ==> Ping fails PING 74.208.192.xxx:80 ==> Ping fails with a message "Ping request could not find host 74.208.192.xxx:80" Both clients A and B are on the same subnet. The server is outside (a virtual server hosted by an ISP) I have an ASP.NET application in a virtual directory on the server. In IE or firefox, if I enter http://74.208.192.xxx/subdir/subdir/../Default.aspx, it works from both the clients! The server has default firewall settings but web server enabled (Port 80 is open).

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• Does Perl auto-vivify variables used as references in subroutine calls?

  - by FM

  I've declared 2010 to be the year of higher-order programming, so I'm learning Haskell. The introduction has a slick quick-sort demo, and I thought, "Hey, that's easy to do in Perl". It turned to be easier than I expected. Note that I don't have to worry about whether my partitions ($less and $more) are defined. Normally you can't use an undefined value as an array reference. use strict; use warnings; use List::MoreUtils qw(part); my @data = (5,6,7,4,2,9,10,9,5,1); my @sorted = qsort(@data); print "@sorted\n"; sub qsort { return unless @_; my $pivot = shift @_; my ($less, $more) = part { $_ < $pivot ? 0 : 1 } @_; # Works, even though $less and $more are sometimes undefined. return qsort(@$less), $pivot, qsort(@$more); } As best I can tell, Perl will auto-vivify a variable that you try to use as a reference -- but only if you are passing it to a subroutine. For example, my call to foo() works, but not the attempted print. use Data::Dumper qw(Dumper); sub foo { print "Running foo(@_)\n" } my ($x); print Dumper($x); # Fatal: Can't use an undefined value as an ARRAY reference. # print @$x, "\n"; # But this works. foo(@$x); # Auto-vivification: $x is now []. print Dumper($x); My questions: Am I understanding this behavior correctly? What is the explanation or reasoning behind why Perl does this? Is this behavior explained anywhere in the docs?

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• when an autoreleased object is actually released?

  - by psebos

  Hi, I am new in objective-c and I am trying to understand memory management to get it right. After reading the excellent Memory Management Programming Guide for Cocoa by apple my only concern is when actually an autoreleased object is released in an iphone/ipod application. My understanding is at the end of a run loop. But what defines a run loop in the application? So I was wondering whether the following piece of code is right. Assume an object @implementation Test - (NSString *) functionA { NSString *stringA; stringA = [[NSString alloc] initWithString:@"Hello" autorelease] return stringA; } - (NSString *) functionB { NSString *stringB; stringB = [self functionA]; return stringB; } - (NSString *) functionC { NSString *stringC; stringC = [self functionB]; return stringC; } - (void)viewDidLoad { [super viewDidLoad]; (NSString *) p = [self functionC]; NSLog(@"string is %@",p); } @end Is this code valid? From the apple text I understand that the NSString returned from functionA is valid in the scope of functionB. I am not sure whether it is valid in functionC and in viewDidLoad. Thanks!

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• Python: Beginning problems

  - by Blogger

  ok so basically i very new to programming and have no idea how to go about these problems help if you will ^^ Numerologists claim to be able to determine a person’s character traits based on the “numeric value” of a name. The value of a name is determined by summing up the values of the letters of the name, where ‘a’ is 1, ‘b’ is 2, ‘c’ is 3 etc., up to ‘z’ being 26. For example, the name “Zelle” would have the value 26 + 5 + 12 + 12 + 5 = 60 (which happens to be a very suspicious number, by the way). Write a program that calculates the numeric value of a single name provided as input. Word count. A common utility on Unix/Linux systems is a small program called “wc”. This program counts the number of lines, words (strings of characters separated by blanks, tabs, or new lines), and characters in a file. Write your own version of this program. The program should accept a file name as input and then print three numbers showing the count of lines, words, and characters in the file.

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• How can I SETF an element in a tree by an accessor?

  - by Willi Ballenthin

  We've been using Lisp in my AI course. The assignments I've received have involved searching and generating tree-like structures. For each assignment, I've ended up writing something like: (defun initial-state () (list 0 ; score nil ; children 0 ; value 0)) ; something else and building my functions around these "states", which are really just nested lists with some loosely defined structure. To make the structure more rigid, I've tried to write accessors, such as: (defun state-score ( state ) (nth 2 state)) This works for reading the value (which should be all I need to do in a nicely functional world. However, as time crunches, and I start to madly hack, sometimes I want a mutable structure). I don't seem to be able to SETF the returned ...thing (place? value? pointer?). I get an error with something like: (setf (state-score *state*) 10) Sometimes I seem to have a little more luck writing the accessor/mutator as a macro: (defmacro state-score ( state ) `(nth 2 ,state)) However I don't know why this should be a macro, so I certainly shouldn't write it as a macro (except that sometimes it works. Programming by coincidence is bad). What is an appropriate strategy to build up such structures? More importantly, where can I learn about whats going on here (what operations affect the memory in what way)?

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• JSF works only with the .xhtml ending

  - by ThreeFingerMark

  Hello, i start with the programming of a JSF Website. At the moment all files have the .xhtml ending. When i go to http://localhost:8080/myProject/start.jsf everything is all right. But when i rename the file from start.xhtml to start.jsf i became a NoClassDefFound Error. What is my mistake? <servlet-name>Faces Servlet</servlet-name> <servlet-class>javax.faces.webapp.FacesServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>*.jsf</url-pattern> </servlet-mapping> <context-param> <param-name>javax.faces.PROJECT_STAGE</param-name> <param-value>Development</param-value> </context-param>

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• Switching to WPF, the best use of time at Visual Studio Launch 2010

  - by Stewbob

  Yes, this is a programming-related question, if a little indirectly (that's why I marked it Community Wiki right away). For better or worse, I am switching from Winforms to WPF in April. I am also going to be in attendance at the Visual Studio Launch in Las Vegas. I have a real need to get up to speed quickly in WPF, so my question is: What sessions are going to be the best use of my time? I've got some picked out already, but I'm looking for some more advice on how to wade through all the marketing fluff and get some real educational value out of these few days. I have not been to one of these events before, so I don't really know how much is marketing hype, and how much is solid content. A couple of the workshops look interesting (VPR02 and VPS02), but I don't know enough about the actual content of these to justify the extra expense right now. Any thoughts there would be appreciated. And yes, I do have WPF learning planned other than just these few days in Vegas, but since I'm going to be there anyway, I want to learn as much as I can in the time available.

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• Very weird C file-handling anomaly

  - by KáGé

  Hello, I got a very weird issue that I cant figure out in my school project, which is the simulation of a simple filesystem in a human-readable textfile. Unfortunately I don't yet have enough time to translate the comments in my code or make it less gibberish, so if you are bothered by that, you don't have to help, I understand. See the code HERE. Now in drive.h, at line 574 is this part: i = getline(); #ifdef DEBUG printf("Free space in all found at %d.\n\n", i); if(drive.disk != NULL){ printf("Disk OK\n\n"); } #endif //write in data state = seekline(i); Before this it finds place for the allocation database entry in the ALL sector (see the "image files" in the mounts folder, this issue was tested on mount_30.efs-dbf), then gets the line with i = getline() fine (getline is in lglobal.h, line 39), but after that any file manipulation (in this case seekline's fseek, but if I comment that out, then the first fprintf after that) crashes the program straight away. I think the file gets somehow corrupted (though the Disk OK message appears) but can't figure out how. I've tried putting i = getline(); into comment, but it didn't make any difference. I've also tried asking at local programming forums but they didn't really help either. The last few lines of the output before it crashes: Dir written. (drive.h line 562) Seekline entered: 268 (called at drive.h line 564) Getline entered. (called at drive.h line 574) Line got: 268. Free space in all found at 268. (drive.h line 576) Seekline entered: 268 (called at drive.h line 582, note that this exact call was run successfully less than 20 lines back. This one should set the pointer to the beginning of the line it is currently in) After this it crashes. Does anyone has any idea of what causes this and how could I fix it? Thank you.

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• Helping Rails Newbies identify version-specific information on web pages

  - by corprew

  I am trying to help some people getting started programming on rails identify which version that advice found on web pages corresponds to, and am seeking advice and/or guides on how to do it so they don't have to rely on me and/or waste time trying outdated advice. Narrative: I am helping some people get up to speed on rails development, and their stock response to running into problems is searching google for advice. They're using 2.3.5 and thinking of moving to 3. The problem they're running into is that there's a lot of advice out there specific to older rails versions (2.2 for example being popular) that isn't identified. I can usually figure out when the pages are old pretty easily, but they can't (yet.) It seems like random web page authors don't identify which version they're using when they're using the current version, and not all pages are dated. This seems to be a general problem that will get worse -- current unadorned advice is usually 2.3.5 and older unadorned advice is 2.2.x at this point, but people are moving / will be moving to version 3 over the next while and newbies will be stuck looking at a bunch of deprecated/incompatible 2.3.x advice without realizing which version it is. Any advice / pointers / telltales?

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• Avoid loading unnecessary data from db into objects (web pages)

  - by GmGr

  Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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• Operation is not valid due to the current state of the object?

  - by Bill

  I am programming in C#; the code was working about a week ago, however it throws an exception and I don't understand at all what could be wrong with it. Var root = new CalculationNode(); -> Throw exception. In the call stack thats the only thing listed, I've been told that it could be that I need a clean build, but I am open to any ideas or suggestions. Thanks, -Bill Update: Exception's Detail System.InvalidOperationException was unhandled by user code Message=Operation is not valid due to the current state of the object. Source=Calculator.Logic StackTrace: at ~.Calculator.Logic.MyBaseExpressionParser.Parse(String expression) in ~\Source\Calculator.Logic\MyBaseExpressionParser.cs:line 44 at ~.Calculator.Logic.Tests.MyBaseCalculatorServiceTests.BasicMathDivision() in ~\Projects\Tests\Calculator.Logic.Tests\MyBaseCalculatorServiceTests.cs:line 60 InnerException: CalculationNode's code: public sealed calss CalculationNode { public CalculationNode() { this.Left = null; this.Right = null; this.Element = new CalculationElement(); } public CalculationNode Left {get;set;} public CalculationNode Right {get;set;} public CalculationElement Element {get; set;} } CalculationElement's code: public sealed class CalculationElement { public CalculationElement() { Value = string.Empty; IsOperator = false; } public string Value {get; set} public bool IsOperator {get; set} }

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• Automatic testing of GUI related private methods

  - by Stein G. Strindhaug

  When it comes to GUI programming (at least for web) I feel that often the only thing that would be useful to unit test is some of the private methods*. While unit testing makes perfect sense for back-end code, I feel it doesn't quite fit the GUI classes. What is the best way to add automatic testing of these? * Why I think the only methods useful to test is private: Often when I write GUI classes they don't even have any public methods except for the constructor. The public methods if any is trivial, and the constructor does most of the job calling private methods. They receive some data from server does a lot of trivial output and feeds data to the constructor of other classes contained inside it, adding listeners that calls a (more or less directly) calls the server... Most of it pretty trivial (the hardest part is the layout: css, IE, etc.) but sometimes I create some private method that does some advanced tricks, which I definitely do not want to be publicly visible (because it's closely coupled to the implementation of the layout, and likely to change), but is sufficiently complicated to break. These are often only called by the constructor or repeatedly by events in the code, not by any public methods at all. I'd like to have a way to test this type of methods, without making it public or resorting to reflection trickery. (BTW: I'm currently using GWT, but I feel this applies to most languages/frameworks I've used when coding for GUI)

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• Returning a variable in a public void...

  - by James Rattray

  Hello, I'm abit new to programming Android App's, however I have come across a problem, I can't find a way to make global variables -unlike other coding like php or VB.NET, are global variables possible? If not can someone find a way (and if possible implement the way into the code I will provide below) to get a value from the variable 'songtoplay' so I can use in another Public Void... Here is the code: final Spinner hubSpinner = (Spinner) findViewById(R.id.myspinner); ArrayAdapter adapter = ArrayAdapter.createFromResource( this, R.array.colours, android.R.layout.simple_spinner_item); adapter .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); hubSpinner.setAdapter(adapter); // hubSpinner.setOnItemSelectedListener(new OnItemSelectedListener() { public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) { //code Object ttestt = hubSpinner.getSelectedItem(); final String test2 = ttestt.toString(); Toast message1 = Toast.makeText(Textbox.this, test2, Toast.LENGTH_LONG); message1.show(); String songtoplay = test2; // Need songtoplay to be available in another 'Public Void' } public void onNothingSelected(AdapterView<?> parentView) { //Code } }); Basically, it gets the value from the Spinner 'hubSpinner' and displays it in a Toast. I then want it to return a value for string variable 'songtoplay' -or find a way to make it global or useable in another Public Void, (Which is will a button, -loading the song to be played) Please help me, Thanks alot. James

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• How to contain the Deepwater Horizon oil spill? [closed]

  - by Yarin

  This is obviously not programming, but it's important and we're smart people, so let's give it a shot. (BP has actually begun soliciting suggestions for how to deal with the crisis http://www.deepwaterhorizonresponse.com/go/doc/2931/546759/, confirming that they don't have a clue) I'll start with my own proposal... Anchored Chute: A large-diameter, collapsible, flexible tube/hose with a wide mouth on one end is anchored over the leak. There's no need for a hermetic seal, the opening just needs to be big enough to form a canopy over the leak area. The rest of the tubing can just be dumped on the sea floor. Since oil is denser than water, the oily water that flows into the mouth eventually inflates the tube and raises the opposite end to the surface, where it can be collected (Like those inflatable dancing air socks at car dealerships). Further buoyancy could be added with floats attached to the tube at intervals. I think this method would not be as susceptible to the problems BP had with the containment dome, where a rigid, metal casing froze up with crystallized hydrates, as we would not be trying to contain the full pressure of the well, but would be using the natural buoyancy of the oil to channel its flow, and with a much larger opening.

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• How to accommodate for the iPhone 4 screen resolution?

  - by dontWatchMyProfile

  This is a programming question! Read on before you vote to close! According to Apple, the iPhone 4 has a new and better screen resolution: 3.5-inch (diagonal) widescreen Multi-Touch display 960-by-640-pixel resolution at 326 ppi This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. Edit: It seems Apple has integrated an switch that allows to tell if an app is highRes or not. Nice. When we develop high-resolution apps, they probably won't work on older devices. And if they do, they would suffer a lot from 4-times the size of any image, having to scale them down in memory.

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• Does this language feature already exists?

  - by Pindatjuh

  I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition; x = a | b; Where x is a variable and a and b are other variables (or static values). if(x == a) { // all references to "x" are essentially references to "a". } if(x == b) { // same but with "b" } if(x != a) { // ... } if(x == a | b) { // guaranteed that "x" is '"a" | "b"'; interacting with "x" // will interact with both "a" and "b". } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not b only remains a). The last block guarantees that x is at least a or b. Further more; | is not the "bitwise or operator", but I've called it the "and/or"-operator. It's definition is: "|" = "and" | "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, is more (mathematical) background information on this operator. It's loosely based on sets.) I do not know if this construction already exists, so that's my question: does this language feature already exists?

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• Do complex JOINs cause high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• OpenCL - incremental summation during compute

  - by user1721997

  I'm absolutelly novice in OpenCL programming. For my app. (molecular simulaton) I wrote a kernel for calculate intermolecular potential of lennard-jones liquid. In this kernel I need to compute cumulative value of the potential of all particles with one: __kernel void Molsim(__global const float* inmatrix, __global float* fi, const int c, const float r1, const float r2, const float r3, const float rc, const float epsilon, const float sigma, const float h1, const float h23) { float fi0; float fi1; float d; unsigned int i = get_global_id(0); //number of particles (typically 2000) if(c!=i) { // potential before particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(inmatrix[c*3]-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+1]-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+2]-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi0=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi0=0; } // potential after particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(r1-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r2-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r3-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi1=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi1=0; } // cumulative difference of potentials fi[0]+=fi1-fi0; } } My problem is in the line: fi[0]+=fi1-fi0;. In the one-element vector fi[0] are wrong results. I read something about sum reduction, but I do not know how to do it during the calculation. Exist any simple solution of my problem?

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