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  • How to get Augmented Reality: A Practical Guide examples working?

    - by Glen
    I recently bought the book: Augmented Reality: A Practical Guide (http://pragprog.com/titles/cfar/augmented-reality). It has example code that it says runs on Windows, MacOS and Linux. But I can't get the binaries to run. Has anyone got this book and got the binaries to run on ubuntu? I also can't figure out how to compile the examples in Ubuntu. How would I do this? Here is what it says to do: Compiling for Linux Refreshingly, there are no changes required to get the programs in this chapter to compile for Linux, but as with Windows, you’ll first have to find your GL and GLUT files. This may mean you’ll have to download the correct version of GLUT for your machine. You need to link in the GL, GLU, and GLUT libraries and provide a path to the GLUT header file and the files it includes. See whether there is a glut.h file in the /usr/include/GL directory; otherwise, look elsewhere for it—you could use the command find / -name "glut.h" to search your entire machine, or you could use the locate command (locate glut.h). You may need to customize the paths, but here is an example of the compile command: gcc -o opengl_template opengl_template.cpp -I /usr/include/GL -I /usr/include -lGL -lGLU -lglut gcc is a C/C++ compiler that should be present on your Linux or Unix machine. The -I /usr/include/GL command-line argument tells gcc to look in /usr/include/GL for the include files. In this case, you’ll find glut.h and what it includes. When linking in libraries with gcc, you use the -lX switch—where X is the name of your library and there is a correspond- ing libX.a file somewhere in your path. For this example, you want to link in the library files libGL.a, libGLU.a, and libglut.a, so you will use the gcc arguments -lGL -lGLU -lglut. These three files are found in the default directory /usr/lib/, so you don’t need to specify their location as you did with glut.h. If you did need to specify the library path, you would add -L to the path. To run your compiled program, type ./opengl_template or, if the current directory is in your shell’s paths, just opengl_template. When working in Linux, it’s important to know that you may need to keep your texture files to a maximum of 256 by 256 pixels or find the settings in your system to raise this limit. Often an OpenGL program will work in Windows but produce a blank white texture in Linux until the texture size is reduced. The above instructions make no sense to me. Do I have to use gcc to compile or can I use eclipse? If I use either eclipse or gcc what do I need to do to compile and run the program?

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  • Illegal Instruction When Programming C++ on Linux

    - by remagen
    Heyo, My program, which does exactly the same thing every time it runs (moves a point sprite into the distance) will randomly fail with the text on the terminal 'Illegal Instruction'. My googling has found people encountering this when writing assembly which makes sense because assembly throws those kinds of errors. But why would g++ be generating an illegal instruction like this? It's not like I'm compiling for Windows then running on Linux (which even then, as long as both are on x86 shouldn't AFAIK cause an Illegal Instruction). I'll post the main file below. I can't reliably reproduce the error. Although, if I make random changes (add a space here, change a constant there) that force a recompile I can get a binary which will fail with Illegal Instruction every time it is run, until I try setting a break point, which makes the illegal instruction 'dissapear'. :( #include <stdio.h> #include <stdlib.h> #include <GL/gl.h> #include <GL/glu.h> #include <SDL/SDL.h> #include "Screen.h" //Simple SDL wrapper #include "Textures.h" //Simple OpenGL texture wrapper #include "PointSprites.h" //Simple point sprites wrapper double counter = 0; /* Here goes our drawing code */ int drawGLScene() { /* These are to calculate our fps */ static GLint T0 = 0; static GLint Frames = 0; /* Move Left 1.5 Units And Into The Screen 6.0 */ glLoadIdentity(); glTranslatef(0.0f, 0.0f, -6); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); glEnable(GL_POINT_SPRITE_ARB); glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE); glBegin( GL_POINTS ); /* Drawing Using Triangles */ glVertex3d(0.0,0.0, 0); glVertex3d(1.0,0.0, 0); glVertex3d(1.0,1.0, counter); glVertex3d(0.0,1.0, 0); glEnd( ); /* Finished Drawing The Triangle */ /* Move Right 3 Units */ /* Draw it to the screen */ SDL_GL_SwapBuffers( ); /* Gather our frames per second */ Frames++; { GLint t = SDL_GetTicks(); if (t - T0 >= 50) { GLfloat seconds = (t - T0) / 1000.0; GLfloat fps = Frames / seconds; printf("%d frames in %g seconds = %g FPS\n", Frames, seconds, fps); T0 = t; Frames = 0; counter -= .1; } } return 1; } GLuint objectID; int main( int argc, char **argv ) { Screen screen; screen.init(); screen.resize(800,600); LoadBMP("./dist/Debug/GNU-Linux-x86/particle.bmp"); InitPointSprites(); while(true){drawGLScene();} }

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  • Is there some way to make variables like $a and $b in regard to strict?

    - by Axeman
    In light of Michael Carman's comment, I have decided to rewrite the question. Note that 11 comments appear before this edit, and give credence to Michael's observation that I did not write the question in a way that made it clear what I was asking. Question: What is the standard--or cleanest way--to fake the special status that $a and $b have in regard to strict by simply importing a module? First of all some setup. The following works: #!/bin/perl use strict; print "\$a=$a\n"; print "\$b=$b\n"; If I add one more line: print "\$c=$c\n"; I get an error at compile time, which means that none of my dazzling print code gets to run. If I comment out use strict; it runs fine. Outside of strictures, $a and $b are mainly special in that sort passes the two values to be compared with those names. my @reverse_order = sort { $b <=> $a } @unsorted; Thus the main functional difference about $a and $b--even though Perl "knows their names"--is that you'd better know this when you sort, or use some of the functions in List::Util. It's only when you use strict, that $a and $b become special variables in a whole new way. They are the only variables that strict will pass over without complaining that they are not declared. : Now, I like strict, but it strikes me that if TIMTOWTDI (There is more than one way to do it) is Rule #1 in Perl, this is not very TIMTOWDI. It says that $a and $b are special and that's it. If you want to use variables you don't have to declare $a and $b are your guys. If you want to have three variables by adding $c, suddenly there's a whole other way to do it. Nevermind that in manipulating hashes $k and $v might make more sense: my %starts_upper_1_to_25 = skim { $k =~ m/^\p{IsUpper}/ && ( 1 <= $v && $v <= 25 ) } %my_hash ;` Now, I use and I like strict. But I just want $k and $v to be visible to skim for the most compact syntax. And I'd like it to be visible simply by use Hash::Helper qw<skim>; I'm not asking this question to know how to black-magic it. My "answer" below, should let you know that I know enough Perl to be dangerous. I'm asking if there is a way to make strict accept other variables, or what is the cleanest solution. The answer could well be no. If that's the case, it simply does not seem very TIMTOWTDI.

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  • How can I improve my select query for storing large versioned data sets?

    - by Jason Francis
    At work, we build large multi-page web applications, consisting mostly of radio and check boxes. The primary purpose of each application is to gather data, but as users return to a page they have previously visited, we report back to them their previous responses. Worst-case scenario, we might have up to 900 distinct variables and around 1.5 million users. For several reasons, it makes sense to use an insert-only approach to storing the data (as opposed to update-in-place) so that we can capture historical data about repeated interactions with variables. The net result is that we might have several responses per user per variable. Our table to collect the responses looks something like this: CREATE TABLE [dbo].[results]( [id] [bigint] IDENTITY(1,1) NOT NULL, [userid] [int] NULL, [variable] [varchar](8) NULL, [value] [tinyint] NULL, [submitted] [smalldatetime] NULL) Where id serves as the primary key. Virtually every request results in a series of insert statements (one per variable submitted), and then we run a select to produce previous responses for the next page (something like this): SELECT t.id, t.variable, t.value FROM results t WITH (NOLOCK) WHERE t.userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') AND t.id IN (SELECT MAX(id) AS id FROM results WITH (NOLOCK) WHERE userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') GROUP BY variable) Which, in this case, would return the most recent responses for the variables "internat", "veteran", and "athlete" for user 2111846. We have followed the advice of the database tuning tools in indexing the tables, and against our data, this is the best-performing version of the select query that we have been able to come up with. Even so, there seems to be significant performance degradation as the table approaches 1 million records (and we might have about 150x that). We have a fairly-elegant solution in place for sharding the data across multiple tables which has been working quite well, but I am open for any advice about how I might construct a better version of the select query. We use this structure frequently for storing lots of independent data points, and we like the benefits it provides. So the question is, how can I improve the performance of the select query? I assume the nested select statement is a bad idea, but I have yet to find an alternative that performs as well. Thanks in advance. NB: Since we emphasize creating over reading in this case, and since we never update in place, there doesn't seem to be any penalty (and some advantage) for using the NOLOCK directive in this case.

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  • Are comonads a good fit for modeling the Wumpus world?

    - by Tim Stewart
    I'm trying to find some practical applications of a comonad and I thought I'd try to see if I could represent the classical Wumpus world as a comonad. I'd like to use this code to allow the Wumpus to move left and right through the world and clean up dirty tiles and avoid pits. It seems that the only comonad function that's useful is extract (to get the current tile) and that moving around and cleaning tiles would not use be able to make use of extend or duplicate. I'm not sure comonads are a good fit but I've seen a talk (Dominic Orchard: A Notation for Comonads) where comonads were used to model a cursor in a two-dimensional matrix. If a comonad is a good way of representing the Wumpus world, could you please show where my code is wrong? If it's wrong, could you please suggest a simple application of comonads? module Wumpus where -- Incomplete model of a world inhabited by a Wumpus who likes a nice -- tidy world but does not like falling in pits. import Control.Comonad -- The Wumpus world is made up of tiles that can be in one of three -- states. data Tile = Clean | Dirty | Pit deriving (Show, Eq) -- The Wumpus world is a one dimensional array partitioned into three -- values: the tiles to the left of the Wumpus, the tile occupied by -- the Wumpus, and the tiles to the right of the Wumpus. data World a = World [a] a [a] deriving (Show, Eq) -- Applies a function to every tile in the world instance Functor World where fmap f (World as b cs) = World (fmap f as) (f b) (fmap f cs) -- The Wumpus world is a Comonad instance Comonad World where -- get the part of the world the Wumpus currently occupies extract (World _ b _) = b -- not sure what this means in the Wumpus world. This type checks -- but does not make sense to me. extend f w@(World as b cs) = World (map world as) (f w) (map world cs) where world v = f (World [] v []) -- returns a world in which the Wumpus has either 1) moved one tile to -- the left or 2) stayed in the same place if the Wumpus could not move -- to the left. moveLeft :: World a -> World a moveLeft w@(World [] _ _) = w moveLeft (World as b cs) = World (init as) (last as) (b:cs) -- returns a world in which the Wumpus has either 1) moved one tile to -- the right or 2) stayed in the same place if the Wumpus could not move -- to the right. moveRight :: World a -> World a moveRight w@(World _ _ []) = w moveRight (World as b cs) = World (as ++ [b]) (head cs) (tail cs) initWorld = World [Dirty, Clean, Dirty] Dirty [Clean, Dirty, Pit] -- cleans the current tile cleanTile :: Tile -> Tile cleanTile Dirty = Clean cleanTile t = t Thanks!

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  • Is 4-5 years the “Midlife Crisis” for a programming career?

    - by Jeffrey
    I’ve been programming C# professionally for a bit over 4 years now. For the past 4 years I’ve worked for a few small/medium companies ranging from “web/ads agencies”, small industry specific software shops to a small startup. I've been mainly doing "business apps" that involves using high-level programming languages (garbage collected) and my overall experience was that all of the works I’ve done could have been more professional. A lot of the things were done incorrectly (in a rush) mainly due to cost factor that people always wanted something “now” and with the smallest amount of spendable money. I kept on thinking maybe if I could work for a bigger companies or a company that’s better suited for programmers, or somewhere that's got the money and time to really build something longer term and more maintainable I may have enjoyed more in my career. I’ve never had a “mentor” that guided me through my 4 years career. I am pretty much blog / google / self taught programmer other than my bachelor IT degree. I’ve also observed another issue that most so called “senior” programmer in “my working environment” are really not that senior skill wise. They are “senior” only because they’ve been a long time programmer, but the code they write or the decisions they make are absolutely rubbish! They don't want to learn, they don't want to be better they just want to get paid and do what they've told to do which make sense and most of us are like that. Maybe that’s why they are where they are now. But I don’t want to become like them I want to be better. I’ve run into a mental state that I no longer intend to be a programmer for my future career. I started to think maybe there are better things out there to work on. The more blogs I read, the more “best practices” I’ve tried the more I feel I am drifting away from “my reality”. But I am not a great programmer otherwise I don't think I am where I am now. I think 4-5 years is a stage that can be a step forward career wise or a step out of where you are. I just wanted to hear what other have to say about what I’ve mentioned above and whether you’ve experienced similar situation in your past programming career and how you dealt with it. Thanks.

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  • Replace text in XSL using wildcards

    - by JosephThomas
    This is similar to an earlier problem I was having which you guys solved in less than a day. I am working with XML files that are generated by a digital video camera. The camera allows the user to save all of the camera's settngs to an SD card so that the settings can be recalled or loaded into another camera. The XSL stylesheet I am writing will allow users to view the camera's settings, as saved to the SD card in a web browser. While most of the values in the XML file -- as formatted by my stylesheet -- make sense to humans, some do not. What I would like to do is have the stylesheet display text that is based on the value in the XML file but more easily understood by humans. A typical value that can be written to the XML file is "_23_970" which represents the camera's frame rate. This would be better displayed as 23.970 (or 023.970). The first underscore is a sort of place holder to make a space for values over 099.999. The second underscore, obviously represents the decimal. My previous (similar) question involved replacing predictable text, and the solution was matching templates. In this case, however, the camera can be set at any one of 119,999 frame rates (I think I did that math correctly). The approach, I would guess, is to pass a value to the displayed webpage that keeps the numeric values (each digit), replaces the second underscore with a decimal, and replaces the first underscore with either an nbsp or a zero (whichever is easier). If the first character in the string is a "1" (the camera can run at frame rates up to 120.000) then the one should be passed on to the page displayed by the stylesheet. I have read other posts here regarding wildcards, but couldn't find one that answered this question. EDIT: Sorry for leaving out important info. I fared better on my first try at asking a question! I guess I got complacent. Anyhow . . . I should have shown you the code that displays the text in the XSL file as is: <tr> <xsl:for-each select="Settings/Groups/Recording"> <tr><td class="title_column">Frame Rate</td><td><xsl:value-of select="RecOutLinkSpeed"/></td></tr> </xsl:for-each> </tr> I should also have given you the URL for the sample file I have been working with: http://josephthomas.info/Alexa/Setup_120511_140322.xml

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  • Database design advice needed.

    - by user346271
    Hi all, I'm a lone developer for a telecoms company, and am after some database design advice from anyone with a bit of time to answer. I am inserting into one table ~2 million rows each day, these tables then get archived and compressed on a monthly basis. Each monthly table contains ~15,000,000 rows. Although this is increasing month on month. For every insert I do above I am combining the data from rows which belong together and creating another "correlated" table. This table is currently not being archived, as I need to make sure I never miss an update to the correlated table. (Hope that makes sense) Although in general this information should remain fairly static after a couple of days of processing. All of the above is working perfectly. However my company now wishes to perform some stats against this data, and these tables are getting too large to provide the results in what would be deemed a reasonable time. Even with the appropriate indexes set. So I guess after all the above my question is quite simple. Should I write a script which groups the data from my correlated table into smaller tables. Or should I store the queries result sets in something like memcache? I'm already using mysqls cache, but due to having limited control over how long the data is stored for, it's not working ideally. The main advantages I can see of using something like memcache: No blocking on my correlated table after the query has been cashed. Greater flexibility of sharing the collected data between the backend collector and front end processor. (i.e custom reports could be written in the backend and the results of these stored in the cache under a key which then gets shared with anyone who would want to see the data of this report) Redundancy and scalability if we start sharing this data with a large amount of customers. The main disadvantages I can see of using something like memcache: Data is not persistent if machine is rebooted / cache is flushed. The main advantages of using MySql Persistent data. Less code changes (although adding something like memcache is trivial anyway) The main disadvantages of using MySql Have to define table templates every time I want to store provide a new set of grouped data. Have to write a program which loops through the correlated data and fills these new tables. Potentially will still grow slower as the data continues to be filled. Apologies for quite a long question. It's helped me to write down these thoughts here anyway, and any advice/help/experience with dealing with this sort of problem would be greatly appreciated. Many thanks. Alan

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  • get attributes from xml tree using linq

    - by nelsonwebs
    I'm working with an xml file that looks like this: <?xml version="1.0" encoding="UTF-8"?> <element1 xmlns="http://namespace1/"> <element2> <element3> <element4 attr1="2009-11-09"> <element5 attr2="NAME1"> <element6 attr3="1"> <element7 attr4="1" attr5="5.5" attr6="3.4"/> </element6> </element5> <element5 attr2="NAME2"> <element6 attr3="1"> <element7 attr4="3" attr5="4" attr6="4.5"/> </element6> </element5> </element4> </element3> </element2> </element1> Where I need to loop through element5 and retrieve the attributes in an Ienumberable like this: attr1, attr2, attr3, attr4, attr5, attr6 using linq to xml and c#. I can loop through the element5 and get all the attribute2 info using but I can't figure out how to get the parent or child attributes I need. UPDATE: Thanks for the feeback thus far. For clarity, I need to do a loop through attribute5. So basically, what I have right now (which isn't much) is . . . XElement xel = XElement.Load(xml); IEnumberable<XElement> cList = from el in xel.Elements(env + "element2").Element (n2 + "element3").Elements(n2 + "element4").Elements(ns + "element5") select el; foreach (XElement e in cList) Console.WriteLine(e.Attribute("attr2").Value.ToString()); This will give me the value all the attr 2 in the loop but I could be going about this all wrong for what I'm trying to acheive. I also need to collect the other attributes mentioned above in a collection (the Console reference is just me playing with this right now but the end result I need is a collection). So the end results would be a collection like attr1, attr2, attr3, attr4, attr5, attr6 2009-11-09, name1, 1, 1, 5.5, 3.4 2009-11-09, name2, 1, 3, 4, 4.5 Make Sense?

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  • PHP Changing Class Variables Outside of Class

    - by Jamie Bicknell
    Apologies for the wording on this question, I'm having difficulties explaining what I'm after, but hopefully it makes sense. Let's say I have a class, and I wish to pass a variable through one of it's methods, then I have another method which outputs this variable. That's all fine, but what I'm after is that if I update the variable which was originally passed, and do this outside the class methods, it should be reflected in the class. I've created a very basic example: class Test { private $var = ''; function setVar($input) { $this->var = $input; } function getVar() { echo 'Var = ' . $this->var . '<br />'; } } If I run $test = new Test(); $string = 'Howdy'; $test->setVar($string); $test->getVar(); I get Var = Howdy However, this is the flow I would like: $test = new Test(); $test->setVar($string); $string = 'Hello'; $test->getVar(); $string = 'Goodbye'; $test->getVar(); Expected output to be Var = Hello Var = Goodbye I don't know what the correct naming of this would be, and I've tried using references to the original variable but no luck. I've come across this in the past, with the PDO prepared statements, see Example #2 $stmt = $dbh->prepare("INSERT INTO REGISTRY (name, value) VALUES (?, ?)"); $stmt->bindParam(1, $name); $stmt->bindParam(2, $value); // insert one row $name = 'one'; $value = 1; $stmt->execute(); // insert another row with different values $name = 'two'; $value = 2; $stmt->execute(); I know I can change the variable to public and do the following, but it isn't quite the same as how the PDO class handles it, and I'm really looking to mimic that behaviour. $test = new Test(); $test->setVar($string); $test->var = 'Hello'; $test->getVar(); $test->var = 'Goodbye'; $test->getVar(); Any help, ideas, pointers, or advice would be greatly appreciated, thanks.

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  • what is the purpose of getEventType() method in XMLStreamReader Class

    - by KItis
    I have sample code written for parsing xml file using javax.xml package. it uses the method called getEventType() , but I can not understand the purpose of this method. i wrote simple application to understand its usefulness, but it output only some random numbers for which I can not make any sense, could some one help me to get this point right. Here is the sample code I have written. public List parseXML(File f) throws XMLStreamException{ xmlInputFactory = new WstxInputFactory(); xmlInputFactory.setProperty(XMLInputFactory2.IS_REPLACING_ENTITY_REFERENCES, Boolean.FALSE); xmlInputFactory.setProperty(XMLInputFactory2.IS_SUPPORTING_EXTERNAL_ENTITIES, Boolean.FALSE); xmlInputFactory.setProperty(XMLInputFactory2.IS_COALESCING,Boolean.FALSE); xmlInputFactory.setProperty(XMLInputFactory2.IS_VALIDATING,Boolean.FALSE); xmlInputFactory.configureForSpeed(); List<Task> tasks = new LinkedList<Task>(); //xmlStreamReader = xmlInputFactory.createXMLStreamReader(new StringReader(dmml)); xmlStreamReader = xmlInputFactory.createXMLStreamReader(f); int eventType = xmlStreamReader.getEventType(); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); eventType = xmlStreamReader.next(); System.out.println(eventType); /*String currentElement = ""; String currentElementText = ""; }

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  • Controlling the USB from Windows

    - by b-gen-jack-o-neill
    Hi, I know this probably is not the easiest thing to do, but I am trying to connect Microcontroller and PC using USB. I dont want to use internal USART of Microcontroller or USB to RS232 converted, its project indended to help me understand various principles. So, getting the communication done from the Microcontroller side is piece of cake - I mean, when I know he protocol, its relativelly easy to implement it on Micro, becouse I am in direct control of evrything, even precise timing. But this is not the case of PC. I am not very familiar with concept of Windows handling the devices connected. In one of my previous question I ask about how Windows works with devices thru drivers. I understood that for internal use of Windows, drivers must have some default set of functions available to OS. I mean, when OS wants to access HDD, it calls HDD driver (which is probably internal in OS), with specific "questions" so that means that HDD driver has to be written to cooperate with Windows, to have write function in the proper place to be called by the OS. Something similiar is for GPU, Even DirectX, I mean DirectX must call specific functions from drivers, so drivers must be written to work with DX. I know, many functions from WinAPI works on their own, but even "simple" window must be in the end written into framebuffer, using MMIO to adress specified by drivers. Am I right? So, I expected that Windows have internal functions, parts of WinAPI designed to work with certain comonly used things. To call manufacturer-designed drivers. But this seems to not be entirely true becouse Windows has no way to communicate thru Paralel port. I mean, there is no function in the WinAPI to work with serial port, but there are funcions to work with HDD,GPU and so. But now there comes the part I am getting very lost at. So, I think Windows must have some built-in functions to communicate thru USB, becouse for example it handles USB flash memory. So, is there any WinAPI function designed to let user to operate USB thru that function, or when I want to use USB myself, do I have to call desired USB-driver function myself? Becouse all you need to send to USB controller is device adress and the infromation right? I mean, I don´t have to write any new drivers, am I right? Just to call WinAPI function if there is such, or directly call original USB driver. Does any of this make some sense?

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  • Specify a base classes template parameters while instantiating a derived class?

    - by DaClown
    Hi, I have no idea if the title makes any sense but I can't find the right words to descibe my "problem" in one line. Anyway, here is my problem. There is an interface for a search: template <typename InputType, typename ResultType> class Search { public: virtual void search (InputType) = 0; virtual void getResult(ResultType&) = 0; }; and several derived classes like: template <typename InputType, typename ResultType> class XMLSearch : public Search<InputType, ResultType> { public: void search (InputType) { ... }; void getResult(ResultType&) { ... }; }; The derived classes shall be used in the source code later on. I would like to hold a simple pointer to a Search without specifying the template parameters, then assign a new XMLSearch and thereby define the template parameters of Search and XMLSearch Search *s = new XMLSearch<int, int>(); I found a way that works syntactically like what I'm trying to do, but it seems a bit odd to really use it: template <typename T> class Derived; class Base { public: template <typename T> bool GetValue(T &value) { Derived<T> *castedThis=dynamic_cast<Derived<T>* >(this); if(castedThis) return castedThis->GetValue(value); return false; } virtual void Dummy() {} }; template <typename T> class Derived : public Base { public: Derived<T>() { mValue=17; } bool GetValue(T &value) { value=mValue; return true; } T mValue; }; int main(int argc, char* argv[]) { Base *v=new Derived<int>; int i=0; if(!v->GetValue(i)) std::cout<<"Wrong type int."<<std::endl; float f=0.0; if(!v->GetValue(f)) std::cout<<"Wrong type float."<<std::endl; std::cout<<i<<std::endl<<f; char c; std::cin>>c; return 0; } Is there a better way to accomplish this?

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  • Problem persisting inheritance tree

    - by alaiseca
    I have a problem trying to map an inheritance tree. A simplified version of my model is like this: @MappedSuperclass @Embeddable public class BaseEmbedded implements Serializable { @Column(name="BE_FIELD") private String beField; // Getters and setters follow } @MappedSuperclass @Embeddable public class DerivedEmbedded extends BaseEmbedded { @Column(name="DE_FIELD") private String deField; // Getters and setters follow } @MappedSuperclass public abstract class BaseClass implements Serializable { @Embedded protected BaseEmbedded embedded; public BaseClass() { this.embedded = new BaseEmbedded(); } // Getters and setters follow } @Entity @Table(name="MYTABLE") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="TYPE", discriminatorType=DiscriminatorType.STRING) public class DerivedClass extends BaseClass { @Id @Column(name="ID", nullable=false) private Long id; @Column(name="TYPE", nullable=false, insertable=false, updatable=false) private String type; public DerivedClass() { this.embedded = new DerivedClass(); } // Getters and setters follow } @Entity @DiscriminatorValue("A") public class DerivedClassA extends DerivedClass { @Embeddable public static NestedClassA extends DerivedEmbedded { @Column(name="FIELD_CLASS_A") private String fieldClassA; } public DerivedClassA() { this.embedded = new NestedClassA(); } // Getters and setters follow } @Entity @DiscriminatorValue("B") public class DerivedClassB extends DerivedClass { @Embeddable public static NestedClassB extends DerivedEmbedded { @Column(name="FIELD_CLASS_B") private String fieldClassB; } public DerivedClassB() { this.embedded = new NestedClassB(); } // Getters and setters follow } At Java level, this model is working fine, and I believe is the appropriate one. My problem comes up when it's time to persist an object. At runtime, I can create an object which could be an instance of DerivedClass, DerivedClassA or DerivedClassB. As you can see, each one of the derived classes introduces a new field which only makes sense for that specific derived class. All the classes share the same physical table in the database. If I persist an object of type DerivedClass, I expect fields BE_FIELD, DE_FIELD, ID and TYPE to be persisted with their values and the remaining fields to be null. If I persist an object of type DerivedClass A, I expect those same fields plus the FIELD_CLASS_A field to be persisted with their values and field FIELD_CLASS_B to be null. Something equivalent for an object of type DerivedClassB. Since the @Embedded annotation is at the BaseClass only, Hibernate is only persisting the fields up to that level in the tree. I don't know how to tell Hibernate that I want to persist up to the appropriate level in the tree, depending on the actual type of the embedded property. I cannot have another @Embedded property in the subclasses since this would duplicate data that is already present in the superclass and would also break the Java model. I cannot declare the embedded property to be of a more specific type either, since it's only at runtime when the actual object is created and I don't have a single branch in the hierarchy. Is it possible to solve my problem? Or should I resignate myself to accept that there is no way to persist the Java model as it is? Any help will be greatly appreciated.

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  • Fastest way to copy a set (100+) of related SQLAlchemy objects and change attribute on each one

    - by rebus
    I am developing an app that keeps track of items going in and out of factory. For example, lets say you have 3 kinds of plastic coming in, they are mixed in various ratios and then sent out as a new product. So to keep track of this I've created following database structure: This is very simplified overview of my SQLAlchemy models: IN <- RATIO <- OUT <- REPORT ITEMS -> REPORT IN are products coming in, RATIO is various information on measurements, and OUT is a final product. REPORT is basically a header model which has a lot of REPORT ITEMS attached to it, which in turn relate it to OUT products. This would all work perfectly, but IN and RATION values can change. These changes ultimately change the OUT product which would mean the REPORT values would change. So in order to change an attribute on IN object for example I should copy that object with that attribute changed. I would think this is basically a question about database normalization, because i didn't want to duplicate all the IN, RATIO and OUT information by writing it in REPORT ITEMS table for example, but I've came across this problem (well not really a problem but rather a feature I'd like for a user to have). When the attribute on IN object is changed I want related objects (RATIO and OUT) automatically copied and related to a new IN object. So I was thinking something like: Take an existing instance of model IN that needs to change (call it old_in) Create a new one out of it with some attributes changed (call it new_in) Collect all the RATIO objects that are related to old_in Copy each RATIO and relate them to a new_in Collect all the OUT objects that are related to old RATIO Copy each OUT and relate them to a new RATIO Few questions pop to mind when i look at this problem: Should i just duplicate the data, does all this copying even make sense? If it does, should i rather do it in plain SQL? If no what would be the best approach to do it with Python and SQLAlchemy? Any general answer would suffice really, at least a pointer in right direction. I really want to free then end user for hassle of having create new ratios and out products.

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  • Can you get a Func<T> (or similar) from a MethodInfo object?

    - by Dan Tao
    I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.) Suppose there exists some class that looks like this: public class MyClass { public string GetName() { return "My Name"; } } Bear with me here. I know that if I have an instance of MyClass called x, I can call x.GetName(). Furthermore, I could set a Func<string> variable to x.GetName. Now here's my question. Let's say I don't know the above class is called MyClass; I've got some object, x, but I have no idea what it is. I could check to see if that object has a GetName method by doing this: MethodInfo getName = x.GetType().GetMethod("GetName"); Suppose getName is not null. Then couldn't I furthermore check if getName.ReturnType == typeof(string) and getName.GetParameters().Length == 0, and at this point, wouldn't I be quite certain that the method represented by my getName object could definitely be cast to a Func<string>, somehow? I realize there's a MethodInfo.Invoke, and I also realize I could always create a Func<string> like: Func<string> getNameFunc = () => getName.Invoke(x, null); I guess what I'm asking is if there's any way to go from a MethodInfo object to the actual method it represents, incurring the performance cost of reflection in the process, but after that point being able to call the method directly (via, e.g., a Func<string> or something similar) without a performance penalty. What I'm envisioning might look something like this: // obviously this would throw an exception if GetActualInstanceMethod returned // something that couldn't be cast to a Func<string> Func<string> getNameFunc = (Func<string>)getName.GetActualInstanceMethod(x); (I realize that doesn't exist; I'm wondering if there's anything like it.) If what I'm asking doesn't make sense, or if I'm being unclear, I'll be happy to attempt to clarify.

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  • Not seeing Sync Block in Object Layout

    - by bob-bedell
    It's my understanding the all .NET object instances begin with an 8 byte 'object header': a synch block (4 byte pointer into a SynchTableEntry table), and a type handle (4 byte pointer into the types method table). I'm not seeing this in VS 2010 RC's (CLR 4.0) debugger memory windows. Here's a simple class that will generate a 16 byte instance, less the object header. class Program { short myInt = 2; // 4 bytes long myLong = 3; // 8 bytes string myString = "aString"; // 4 byte object reference // 16 byte instance static void Main(string[] args) { new Program(); return; } } An SOS object dump tells me that the total object size is 24 bytes. That makes sense. My 16 byte instance plus an 8 byte object header. !DumpObj 0205b660 Name: Offset_Test.Program MethodTable: 000d383c EEClass: 000d13f8 Size: 24(0x18) bytes File: C:\Users\Bob\Desktop\Offset_Test\Offset_Test\bin\Debug\Offset_Test.exe Fields: MT Field Offset Type VT Attr Value Name 632020fc 4000001 10 System.Int16 1 instance 2 myInt 632050d8 4000002 4 System.Int64 1 instance 3 myLong 631fd2b8 4000003 c System.String 0 instance 0205b678 myString Here's the raw memory: 0x0205B660 000d383c 00000003 00000000 0205b678 00000002 ... And here are some annotations: offset 0 000d383c ;TypeHandle (pointer to MethodTable), 4 bytes offset 4 00000003 00000000 ;myLong, 8 bytes offset 12 0205b678 ;myString, 4 byte reference to address of "myString" on GC Heap offset 16 00000002 ;myInt, 4 bytes My object begins a address 0x0205B660. But I can only account for 20 bytes of it, the type handle and the instance fields. There is no sign of a synch block pointer. The object size is reported as 24 bytes, but the debugger is showing that it only occupies 20 bytes of memory. I'm reading Drill Into .NET Framework Internals to See How the CLR Creates Runtime Objects, and expected the first 4 bytes of my object to be a zeroed synch block pointer, as shown in Figure 8 of that article. Granted, this is an article about CLR 1.1. I'm just wondering if the difference between what I'm seeing and what this early article reports is a change in either the debugger's display of object layout, or in the way the CLR lays out objects in versions later than 1.1. Anyway, can anyone account for my 4 missing bytes?

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  • Data Annotations validation Built into model

    - by Josh
    I want to build an object model that automatically wires in validation when I attempt to save an object. I am using DataAnnotations for my validation, and it all works well, but I think my inheritance is whacked. I am looking here for some guidance on a better way to wire in my validation. So, to build in validation I have this interface public interface IValidatable { bool IsValid { get; } ValidationResponse ValidationResults { get; } void Validate(); } Then, I have a base class that all my objects inherit from. I did a class because I wanted to wire in the validation calls automatically. The issue is that the validation has to know the type of the class is it validating. So I use Generics like so. public class CoreObjectBase<T> : IValidatable where T : CoreObjectBase<T> { #region IValidatable Members public virtual bool IsValid { get { // First, check rules that always apply to this type var result = new Validator<T>().Validate((T)this); // return false if any violations occurred return !result.HasViolations; } } public virtual ValidationResponse ValidationResults { get { var result = new Validator<T>().Validate((T)this); return result; } } public virtual void Validate() { // First, check rules that always apply to this type var result = new Validator<T>().Validate((T)this); // throw error if any violations were detected if (result.HasViolations) throw new RulesException(result.Errors); } #endregion } So, I have this circular inheritance statement. My classes look like this then: public class MyClass : CoreObjectBase<MyClass> { } But the problem occurs when I have a more complicated model. Because I can only inherit from one class, when I have a situation where inheritance makes sense I believe the child classes won't have validation on their properties. public class Parent : CoreObjectBase<Parent> { //properties validated } public class Child : Parent { //properties not validated? } I haven't really tested the validation in these cases yet, but I am pretty sure that anything in child with a data annotation on it will not be automatically validated when I call Child.Validate(); due to the way the inheritance is configured. Is there a better way to do this?

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  • jquery animation problem using stop

    - by Flanders
    Hi! When running a Jquery animation like slideDown(), it looks like a number of element-specific css properties is set to be updated at a specific interval and when the animation is complete these properties are unset and the display property is simply set to auto or whatever. At least in firebug you can't see those temporary properties any more. The problem I've encountered is the scenario where we stop the slide down with stop(). The element is then left with the current temporary css values. Which is fine because it has to, but let us say that I stoped the slidedown because I have decided to slide it back up again a bit prematurely. It would look something like this: $(this).slideDown(2000) //The below events is not in queue but will rather start execute almost simultaneously as the above line. (dont remember the exact syntax) $(this).delay(1000).stop().slideUp(2000) The above code might not make much sense, but the point is: After 1 second of sliding down the animation is stopped and it starts to slide back up. Works like a charm. BUT!!! And here is the problem. Once it it has slid back up the elements css properties are reset to the exact values it had 1000ms into the slideDown() animation (when stop() was called). If we now try to run the following: $(this).slideDown(2000) It will slide down to the very point the prior slideDown was aborted and not further at half the speed (since it uses the same time for approximately half the height). This is because the css properties were saved as I see it. But it is not especially wished for. Of course I want it to slide all the way down this time. Due to UI interaction that is hard to predict everything might soon break. The longer animations we use increases the risk of something like this happening. Is this to be considered a bug, or am I doing something wrong? Or maybe it's just a feature that is not supported? I guess I can use a callback function to reset the css properties, but depending on the animation used, different css properties are used to render it, and covering your back would result in quite a not-so-fancy solution.

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  • C++ constructor problem, values not being set

    - by 2Real
    Hi, I'm new to C++ and I'm trying to figure out this problem I'm having with my constructor for one of my classes. What happens is... all my variables are initialized properly except two (health and type). #pragma once #include <irrlicht.h> #include <vector> #include <cassert> using namespace irr; using namespace core; using namespace scene; enum { PLAYER = 0, NPC = 1, SOLDIER = 2, CHAINGUNNER = 3 }; class Model { public: Model(void); Model(int id, std::vector<ISceneNode*> modelVec, int modType); ~Model(void); std::vector<int> path; std::vector<ISceneNode*> model; int endNode; int type; int animate; int health; u32 lastAnimation; private: int mId; }; #include "Model.h" Model::Model(void) { //assert(false); } Model::Model(int id, std::vector<ISceneNode*> modelVec, int modType) { path = std::vector<int>(); model = modelVec; endNode = 0; type = modType; animate = 0; health = 100; lastAnimation = 0; mId = id; } Model::~Model(void) {} I create a model with Model soldier(id, model, SOLDIER) Everything is set properly except type and health. I've tried many different things, but I cannot figure out my problem. I'm not sure but the default constructor is being called. It doesn't make sense because I make no called to that constructor. Thanks,

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  • Jquery remove class from image

    - by user1269625
    Hey ya'll I have these 3 images thumbnails here... <div class="wpcart_gallery" style="text-align:center; padding-top:5px;"> <a class="thickbox cboxElement" title="DSC_0118" href="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/DSC_0118.jpg" rel="Teardrop Druzy Amethyst Ring" rev="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/DSC_0118.jpg"> <img class="attachment-gold-thumbnails colorbox-736" width="50" height="50" title="DSC_0118" alt="DSC_0118" src="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/DSC_0118-50x50.jpg"> </a> <a class="thickbox cboxElement" title="P7230376" href="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230376.jpg" rel="Teardrop Druzy Amethyst Ring" rev="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230376.jpg"> <img class="attachment-gold-thumbnails colorbox-736" width="50" height="50" title="P7230376" alt="P7230376" src="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230376-50x50.jpg"> </a> <a class="thickbox cboxElement" title="P7230378" href="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230378.jpg" rel="Teardrop Druzy Amethyst Ring" rev="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230378.jpg"> <img class="attachment-gold-thumbnails colorbox-736" width="50" height="50" title="P7230378" alt="P7230378" src="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/P7230378-50x50.jpg"> </a> </div> What I am trying to do is come up with a jquery code that would remove the cboxElement from the first image and if I click on one of the images to remove cboxElement and place cboxElement to the other images... I also have this big image and when you click on one of the thumbnails, the image is replaced by the thumbnail and thats really the thumbnail I want to exclude...Could I possible just say if one of the 3 images src = this one image = src remove the class from this thumbnail? Which way would be better? I am very new at jquery :( I hope this makes sense. Here is the code for the big image... <a class="preview_link cboxElement" style="text-decoration:none;" href="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/DSC_0118.jpg" rel="Teardrop Druzy Amethyst Ring"> <img id="product_image_736" class="product_image colorbox-736" width="400" src="http://www.taranmarlowjewelry.com/wp-content/uploads/2012/07/DSC_0118.jpg" title="Teardrop Druzy Amethyst Ring" alt="Teardrop Druzy Amethyst Ring"> <br> <div style="text-align:center; color:#F39B91;">Click To Enlarge</div> </a> Any help or a point in the right direction would be awesome!!

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  • Correct use of a "for...in" loop in javascript?

    - by jnkrois
    Hello everybody, before I ask my question I wanted to let everybody know that I appreciate the fact that there's always somebody out there willing to help, and on my end I'll try to give back to the community as much as I can. Thanks Now, I would like to get some pointers as to how to properly take advantage of the "for...in" loop in JavaScript, I already did some research and tried a couple things but it is still not clear to me how to properly use it. Let's say I have a random number of "select" tags in an HTML form, and I don't require the user to select an option for all of them, they can leave some untouched if they want. However I need to know if they selected none or at least one. The way I'm trying to find out if the user selected any of them is by using the "for...in" loop. For example: var allSelected = $("select option:selected"); var totalSelected = $("select option:selected").length; The first variable produces an array of all the selected options. The second variable tells me how many selected options I have in the form (select tags could be more than one and it changes every time). Now, in order to see if any has been selected I loop through each element (selected option), and retrieve the "value" attribute. The default "option" tag has a value="0", so if any selected option returns a value greater than 0, I know at least one option has been selected, however it does not have to be in order, this is my loop so far: for(var i = 0; i < totalSelected; i++){ var eachOption = $(allSelected[i]).val(); var defaultValue = 0; if(eachOption == defaultValue){ ...redirect to another page }else if(eachOption > defaultValue){ ... I display an alert } } My problem here is that as soon as the "if" matches a 0 value, it sends the user to the next page without testing the rest of the elements in the array, and the user could have selected the second or third options. What I really want to do is check all the elements in the array and then take the next action, in my mind this is how I could do it, but I'm not getting it right: var randomValue = 25; for(randomValue in allSelected){ var found = true; var notFound = false if(found){ display an alert }else{ redirect to next page } } This loop or the logic I'm using are flawed (I'm pretty sure), what I want to do is test all the elements in the array against a single variable and take the next action accordingly. I hope this makes some sense to you guys, any help would be appreciated. Thanks, JC

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  • C++0x class factory with variadic templates problem

    - by randomenglishbloke
    I have a class factory where I'm using variadic templates for the c'tor parameters (code below). However, when I attempt to use it, I get compile errors; when I originally wrote it without parameters, it worked fine. Here is the class: template< class Base, typename KeyType, class... Args > class GenericFactory { public: GenericFactory(const GenericFactory&) = delete; GenericFactory &operator=(const GenericFactory&) = delete; typedef Base* (*FactFunType)(Args...); template <class Derived> static void Register(const KeyType &key, FactFunType fn) { FnList[key] = fn; } static Base* Create(const KeyType &key, Args... args) { auto iter = FnList.find(key); if (iter == FnList.end()) return 0; else return (iter->second)(args...); } static GenericFactory &Instance() { static GenericFactory gf; return gf; } private: GenericFactory() = default; typedef std::unordered_map<KeyType, FactFunType> FnMap; static FnMap FnList; }; template <class B, class D, typename KeyType, class... Args> class RegisterClass { public: RegisterClass(const KeyType &key) { GenericFactory<B, KeyType, Args...>::Instance().Register(key, FactFn); } static B *FactFn(Args... args) { return new D(args...); } }; Here is the error: when calling (e.g.) // Tucked out of the way RegisterClass<DataMap, PDColumnMap, int, void *> RC_CT_PD(0); GCC 4.5.0 gives me: In constructor 'RegisterClass<B, D, KeyType, Args>::RegisterClass(const KeyType&) [with B = DataMap, D = PDColumnMap, KeyType = int, Args = {void*}]': no matching function for call to 'GenericFactory<DataMap, int, void*>::Register(const int&, DataMap* (&)(void*))' I can't see why it won't compile and after extensive googling I couldn't find the answer. Can anyone tell me what I'm doing wrong (aside from the strange variable name, which makes sense in context)?

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  • Advice needed: stay with Java team or move to C++ team?

    - by user68759
    Some background - I have been programming in Java as a professional for the last few years. This is mainly using Java SE. I have also touched bits and pieces of other various Java technologies and have some basic knowledge about them. I consider my self as an intermediate Java programmer. I like Java very much. I think it is only going to get bigger. Recently, my manager asked my opinion on whether I would like to be transferred to another team within the company that is developing a product in C++. This is mainly because my current Java team simply didn't make enough money due to poor sales and the economic downturn. Now, I have never had any experience with C++ nor have I ever coded a single line of code in C++. I have always wanted to learn it and now is my chance. But I really want to make sure I get benefit out of it in the future, in the sense that I will have the skills that will still be on-demand in the future. So, what do you experts think? Is C++ still the language to learn these days to secure yourself for the future? What will I learn more in C++ but not in Java? And are they worthy to learn considering the current and possible future demands in IT industry? (Apart from the obvious more control over memory management and something along that line.) What is a good excuse to refuse the offer in order to stay with the Java team? I don't want to blatantly refuse it because you can never predict the future and I could possibly come back to my manager in the future and ask him to transfer me to the C++ team. How do I say it nicely that I am taking the offer but I would like to still be involved with Java one way or another, such as when there is a new Java project I would like to be considered. I have to admit that I am kind of 50-50 at the moment. I want to learn C++ for the sake of improving my skills and also helping my company to reduce the fund required for the Java team. But it is also hard for me to leave Java because I know Java is going to get bigger, so I am afraid of getting behind when I start concentrating on C++. I could, of course, decide to just join the C++ team, and then spend my free time reading about Java to keep in touch with it, but I thought I would ask anyway in case some people can point out the strong points of either over the other given the current and possibly future circumstances.

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  • Beginner Android Dev question navigating through intents, getting errors not sure how to fix it. I've tried rearranging and everything even tabbing.

    - by user554786
    /*I created this Sign-In page. I start by declaring variables for username/password & buttons. If user enters "test" as username & "test" as password and hits the login button, its supposed to go to the DrinksTwitter.class activity, else throw error message I created. To me the code and login makes perfect sense. I'm not sure why it wont go to the next activity I want it to go to */ package com.android.drinksonme; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class Screen2 extends Activity { // Declare our Views, so we can access them later private EditText etUsername; private EditText etPassword; private Button btnLogin; private Button btnSignUp; private TextView lblResult; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // Get the EditText and Button References etUsername = (EditText)findViewById(R.id.username); etPassword = (EditText)findViewById(R.id.password); btnLogin = (Button)findViewById(R.id.login_button); btnSignUp = (Button)findViewById(R.id.signup_button); lblResult = (TextView)findViewById(R.id.result); // Check Login String username = etUsername.getText().toString(); String password = etPassword.getText().toString(); if(username.equals("test") && password.equals("test")){ final Intent i = new Intent(Screen2.this, DrinksTwitter.class); btnLogin.setOnClickListener(new OnClickListener() { public void onClick(View v) { startActivity(i); } // lblResult.setText("Login successful."); else { /* ERROR- Syntax error on token "else", { expected */ lblResult.setText("Invalid username or password."); } } }); final Intent k = new Intent(Screen2.this, SignUp.class); btnSignUp.setOnClickListener(new OnClickListener() { public void onClick(View v) { startActivity(k); } }); /* ERROR- Syntax error, insert "}" to complete Statement*/ } }

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