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  • An interesting case of delete and destructor (C++)

    - by Viet
    I have a piece of code where I can call destructor multiple times and access member functions even the destructor was called with member variables' values preserved. I was still able to access member functions after I called delete but the member variables were nullified (all to 0). And I can't double delete. Please kindly explain this. Thanks. #include <iostream> using namespace std; template <typename T> void destroy(T* ptr) { ptr->~T(); } class Testing { public: Testing() : test(20) { } ~Testing() { printf("Testing is being killed!\n"); } int getTest() const { return test; } private: int test; }; int main() { Testing *t = new Testing(); cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; delete t; cout << "t->getTest() = " << t->getTest() << endl; destroy(t); cout << "t->getTest() = " << t->getTest() << endl; t->~Testing(); cout << "t->getTest() = " << t->getTest() << endl; //delete t; // <======== Don't do it! Double free/delete! cout << "t->getTest() = " << t->getTest() << endl; return 0; }

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  • MapReduce for counting parameter values

    - by cnkt
    I have document like this: { "_id": ObjectId("4d17c7963ffcf60c1100002f"), "title": "Text", "params": { "brand": "BMW", "model": "i3" } } { "_id": ObjectId("4d17c7963ffcf60c1100002f"), "title": "Text", "params": { "brand": "BMW", "model": "i5" } } What i need is the count of every params values. like: brand --------- BMW (2) model --------- i3 (1) i5 (1) I think i have to write map/reduce functions. How can i do this? Thanks.

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  • Shaders with pygtkglext

    - by qba
    Do someone know how to get glsl shaders work in gtk-opengl window? With glut all glCreateProgram etc. functions works, but when I tried to put the same gl code into pygtkglext window, its complaining about NullReference: OpenGL.error.NullFunctionError: Attempt to call an undefined function glCreateProgram, check for bool(glCreateProgram) before calling So then I from OpenGL.GL.ARB.shader_objects import *, but the result is similar: OpenGL.error.NullFunctionError: Attempt to call an undefined function glCreateProgramObjectARB, check for bool(glCreateProgramObjectARB) before calling Any idea will be useful.

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  • Underscore before theme name

    - by Nick Lowman
    Hi There, I was browsing the template.php file for the rootcandy theme and noticed some of the function names start with an underscore i.e. function _rootcandy_admin_links() function rootcandy_body_class() Anyone know why this is? I thought the functions had to start with the name of the theme. Many thanks

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  • Can I migrate from ClearCase to Serena VM?

    - by Rich B
    I have a repository using Rational ClearCase Explorer 2003.06.10+ which I want to migrate into Serena ChangeMan Version Manager 8.1.4.2. Is this possible? The ClearCase repository was not used for all it's functions, just as a place to hold copies of documents, so the only thing I need to keep is the files and their version histories.

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  • Flex AS3: ProgressBar doesn't move

    - by jolierouge
    Hey All, I am a little stuck and need some advice/help. I have a progress bar: <mx:ProgressBar id="appProgress" mode="manual" width="300" label="{appProgressMsg}" minimum="0" maximum="100"/> I have two listener functions, one sets the progress, and one sets the appProgressMsg: public function incProgress(e:TEvent):void { var p:uint = Math.floor(e.data.number / e.data.total * 100); trace("Setting Perc." + p); appProgress.setProgress(p, 100); } public function setApplicationProgressStep(e:TEvent):void { trace("Setting step:" + e.data); appProgressMsg = e.data; } I want to reuse this progress bar alot. And not necessarily for ProgressEvents, but when going through steps. For instance, I loop over a bunch of database inserts, and want to undate the progress etc. Here is a sample: public function updateDatabase(result:Object):void { var total:int = 0; var i:int = 0; var r:SQLResult; trace("updateDatabase called."); for each (var table:XML in this.queries.elements("table")) { var key:String = table.attribute("name"); if (result[key]) { send(TEvent.UpdateApplicationProgressStep, "Updating " + key); i = 1; total = result[key].length; for each (var row:Object in result[key]) { //now, we need to see if we already have this record. send(TEvent.UpdateApplicationProgress, { number:i, total: total } ); r = this.query("select * from " + key + " where server_id = '" + row.id + "'"); if (r.data == null) { //there is no entry with this id, make one. this.query(table.insert, row); } else { //it exists, so let's update. this.update(key, row); } i++; } } } } Everything works fine. That is, the listener functions are called and I get trace output like: updateDatabase called. Setting step:Updating project Setting Perc 25 Setting Perc 50 Setting Perc 75 Setting Perc 100 The issue is, only the very last percent and step is shown. that is, when it's all done, the progress bar jumps to 100% and shows the last step label. Does anyone know why this is? Thanks in advance for any help, Jason

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  • Need guidelines for optimizing WebGL performance by minimizing shader changes

    - by brainjam
    I'm trying to get an idea of the practicality of WebGL for rendering large architectural interior scenes, consisting of 100K's of triangles. These triangles are distributed over many objects, and there are many materials in the scene. On the other hand, there are no moving parts. And the materials tend to be fairly simple, mostly based on texture maps. There is a lot of texture map sharing .. for example all the chairs in scene will share a common map. There is also some multitexturing - up to three textures overlaid in a material. I've been doing a little experimentation and reading, and gather that frequently switching materials during a rendering pass will slow things down. For example, a scene with 200K triangles will have significant performance differences, depending on whether there are 10 or 1000 objects, assuming that each time an object is displayed a new material is set up. So it seems that if performance is important the scene should be sorted by materials so as to minimize material switching. What I'm looking for is guidelines on how to think of the overhead of various state changes, and where do I get the biggest bang for the buck. For example, what are the relative performance costs of, say, gl.useProgram(), gl.uniformMatrix4fv(), gl.drawElements() should I try to write ubershaders to minimize shader switching? should I try to aggregate geometry to minimize the number of gl.drawElements() calls I realize that mileage may vary depending on browser, OS, and graphics hardware. And I'm also not looking for heroic measures. Just some guidelines from people who have already had some experience in making scenes fast. I'll add that while I've had some experience with fixed-pipeline OpenGL programming in the past, I'm rather new to the WebGL/OpenGL ES 2.0 way of doing things.

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  • jQuery Validation Arguments

    - by Idsa
    jQuery Validation plugin has "element" argument for required rule. I know how to use it for inline functions but what if I want to pass it to out-of-line JS function? I tried this: rules: { startHours: { required: startTimeRequired(element) }, but it didn't work.

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  • Rails Active Record Mysql find query HAVING clause

    - by meetraghu28
    Is there a way to use the HAVING clause in some other way without using group by. I am using rails and following is a sample sccenario of the problem that i am facing. In rails you can use the Model.find(:all,:select,conditions,:group) function to get data. In this query i can specify a having clause in the :group param. But what if i dont have a group by clause but want to have a having clause in the result set. Ex: Lets take a query select sum(x) as a,b,c from y where "some_conditions" group by b,c; This query has a sum() aggregation on one of the fields. No if there is nothing to aggregate then my result should be an empty set. But mysql return a NULL row. So this problem can be solved by using select sum(x) as a,b from y where "some_conditions" group by b having a NOT NULL; but what happens in case i dont have a group by clause?? a query like below select sum(x) as a,b from y where "some_conditions"; so how to specify that sum(x) should not be NULL? Any solution that would return an empty set in this case instead of a NULL row will help and also that solution should be doable in rails. We can use subqueries to get this condition working with sumthin like this select * from ((select sum(x) as b FROM y where "some_condition") as subq) where subq.b is not null; but is there a better way to do this thru sql/rails ??

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  • What is a good platform for building a game framework targetting both web and native languages?

    - by fuzzyTew
    I would like to develop (or find, if one is already in development) a framework with support for accelerated graphics and sound built on a system flexible enough to compile to the following: native ppc/x86/x86_64/arm binaries or a language which compiles to them javascript actionscript bytecode or a language which compiles to it (actionscript 3, haxe) optionally java I imagine, for example, creating an API where I can open windows and make OpenGL-like calls and the framework maps this in a relatively efficient manner to either WebGL with a canvas object, 3d graphics in Flash, OpenGL ES 2 with EGL, or desktop OpenGL in an X11, Windows, or Cocoa window. I have so far looked into these avenues: Building the game library in haXe Pros: Targets exist for php, javascript, actionscript bytecode, c++ High level, object oriented language Cons: No support for finally{} blocks or destructors, making resource cleanup difficult C++ target does not allow room for producing highly optimized libraries -- the foreign function interface requires all primitive types be boxed in a wrapper object, as if writing bindings for a scripting language; these feel unideal for real-time graphics and audio, especially exporting low-level functions. Doesn't seem quite yet mature Using the C preprocessor to create a translator, writing programs entirely with macros Pros: CPP is widespread and simple to use Cons: This is an arduous task and probably the wrong tool for the job CPP implementations differ widely in support for features (e.g. xcode cpp has no variadic macros despite claiming C99 compliance) There is little-to-no room for optimization in this route Using llvm's support for multiple backends to target c/c++ to web languages Pros: Can code in c/c++ LLVM is a very mature highly optimizing compiler performing e.g. global inlining Targets exist for actionscript (alchemy) and javascript (emscripten) Cons: Actionscript target is closed source, unmaintained, and buggy. Javascript targets do not use features of HTML5 for appropriate optimization (e.g. linear memory with typed arrays) and are immature An LLVM target must convert from low-level bytecode, so high-level constructs are lost and bloated unreadable code is created from translating individual instructions, which may be more difficult for an unprepared JIT to optimize. "jump" instructions cause problems for languages with no "goto" statements. Using libclang to write a translator from C/C++ to web languages Pros: A beautiful parsing library providing easy access to the code structure Can code in C/C++ Has sponsored developer effort from Apple Cons: Incomplete; current feature set targets IDEs. Basic operators are unexposed and must be manually parsed from the returned AST element to be identified. Translating code prior to compilation may forgo optimizations assumed in c/c++ such as inlining. Creating new code generators for clang to translate into web languages Pros: Can code in C/C++ as libclang Cons: There is no API; code structure is unstable A much larger job than using libclang; the innards of clang are complex Building the game library in Common Lisp Pros: Flexible, ancient, well-developed language Extensive introspection should ease writing translators Translators exist for at least javascript Cons: Unfamiliar language No standardized library functions, widely varying implementations Which of these avenues should I pursue? Do you know of any others, or any systems that might be useful? Does a general project like this exist somewhere already? Thank you for any input.

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  • why do i see THROW in a C library

    - by Bhagya
    When I do: less /usr/include/stdio.h (which is only a C library - nothing to do with C++) I see __THROW after quite a few function declarations. Also, comments above a few functions say that 'This function is a possible cancellation point and therefore not marked with __THROW' What is all this for? THROW is meant to be for exception handling.. but as far as I know, C doesn't provide any support for it... Plz explain.

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  • Tools, scripts for working with MS SQL 2008

    - by hgulyan
    Hi, While working with DB, I find useful using some tools, that help me to solve DB problems. Some of them are: 1) Insert generator 2) A tool that can execute a script on a list of DB's 3) Finding a text in stored procedures and functions. 4) DB Back up scripts My question is, what are most useful tools, scripts(anything else), that help you to work with MS SQL? Thanks in advance.

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  • UIScrollView - Figuring out where the scroll will stop

    - by spin-docta
    I'm trying to figure out how to calculate where the scrollview will stop when a user does a swipe gesture and the scrollview goes into deceleration. I'm trying to use the delegate functions, but I can't accurately figure it out. Please help! - (void) scrollViewDidScroll:(UIScrollView *)scrollView; - (void) scrollViewWillBeginDecelerating:(UIScrollView *)scrollView; - (void) scrollViewDidEndDecelerating:(UIScrollView *)scrollView;

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  • Would this method work to scale out SQL queries?

    - by David
    I have a database containing a single huge table. At the moment a query can take anything from 10 to 20 minutes and I need that to go down to 10 seconds. I have spent months trying different products like GridSQL. GridSQL works fine, but is using its own parser which does not have all the needed features. I have also optimized my database in various ways without getting the speedup I need. I have a theory on how one could scale out queries, meaning that I utilize several nodes to run a single query in parallel. The idea is to take an incoming SQL query and simply run it exactly like it is on all the nodes. When the results are returned to a coordinator node, the same query is run on the union of the resultsets. I realize that an aggregate function like average need to be rewritten into a count and sum to the nodes and that the coordinator divides the sum of the sums with the sum of the counts to get the average. What kinds of problems could not easily be solved using this model. I believe one issue would be the count distinct function. Edit: I am getting so many nice suggestions, but none have addressed the method.

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  • Does Scheme work with Microsoft COM?

    - by Martin
    I'm new to Scheme -- the functional programming language and I like it a lot for its first-class/higher-order functions. However, my data comes from a COM source with an object-oriented API. I know Scheme and COM belong to different programming paradigms, but I'm wondering if there is any interface or a way for Scheme to connect to a COM source? Thanks.

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  • PHP Arrays: A good way to check if an array is associative or sequential?

    - by Wilco
    PHP treats all arrays as associative, so there aren't any built in functions. Can anyone recommend a fairly efficient way to check if an array contains only numeric keys? Basically, I want to be able to differentiate between this: $sequentialArray = array('apple', 'orange', 'tomato', 'carrot'); and this: $assocArray = array('fruit1' => 'apple', 'fruit2' => 'orange', 'veg1' => 'tomato', 'veg2' => 'carrot');

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  • Go from a ViewController, to an other section of a TabBar

    - by Seraphin
    Hi, I'm currently doing an application with 5 View Controllers and a tabBar on the bottom. For this application, I need to set up a button in viewController(1) which can send me to an other viewController(3), but without touching the tabBar (it will be hidden for the viewController(1)). I basically know how to use a tabBar, but I don't know wich functions I can use to do that. Thanks in advance! Séraphin

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