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  • Better code for accessing fields in a matlab structure array?

    - by John
    I have a matlab structure array Modles1 of size (1x180) that has fields a, b, c, ..., z. I want to understand how many distinct values there are in each of the fields. i.e. max(grp2idx([foo(:).a])) The above works if the field a is a double. {foo(:).a} needs to be used in the case where the field a is a string/char. Here's my current code for doing this. I hate having to use the eval, and what is essentially a switch statement. Is there a better way? names = fieldnames(Models1); for ix = 1 : numel(names) className = eval(['class(Models1(1).',names{ix},')']); if strcmp('double', className) || strcmp('logical',className) eval([' values = [Models1(:).',names{ix},'];']); elseif strcmp('char', className) eval([' values = {Models1(:).',names{ix},'};']); else disp(['Unrecognized class: ', className]); end % this line requires the statistics toolbox. [g, gn, gl] = grp2idx(values); fprintf('%30s : %4d\n',names{ix},max(g)); end

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  • Enterprise integration of disparate systems

    - by Chris Latta
    We're about to embark on a fairly large integration effort to kill off a bunch of Access and Sql Server databases and get everything into one coherent enterprise system. There are also a number of other systems (accounting, CRM, payroll, MS Exchange) that hold critical data that we need to integrate (use for data validation in other systems), report on and otherwise expose. It is likely that some of these systems will change in the next few years, so we need to isolate our systems to be ready for change. Ideally we would be able to expose our forms in a consistent manner across as many of our our systems as possible without having to re-develop them for each system. We are currently targeting SharePoint (2007 and soon 2010), Office (2007 and soon 2010 - Word, Excel, PowerPoint and Outlook), Reporting Services, .Net console applications, .Net Windows applications, shell extensions, and with the possibility of exposing some functionality on mobile devices (BlackBerries currently, maybe iPhones later) and via our website. We're moving development to Visual Studio 2010 (from 2005) ahead of migrating to SharePoint 2010 and Office 2010. Given that most of our development is presently targeted to the .Net framework (mostly in C#) it seems logical to stick with this unless there is some compelling reason to switch frameworks/platform for some aspects. We're thinking of your standard Database-Data Integration layer-Business Objects Layer-Web Services (or REST) layer-Client Application plus doing our own client application with WPF (or something else?) forms that can also be exposed in the MS systems (SharePoint, Office, Windows). So, we don't want much, just everything :) Basically we need to isolate ourselves from database and systems changes, create an API that can be used throughout our systems and then make this functionality available in our client applications. I'm very keen to get pointers from anyone who has tips on how to pull this off. Should we look at the Enterprise Library as a place to start? Is REST with ASP.Net MVC2 a better solution than Web Services for a system like this? Will WPF deliver forms re-use or is there something better?

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  • Instrumenting a string

    - by George Polevoy
    Somewhere in C++ era i have crafted a library, which enabled string representation of the computation history. Having a math expression like: TScalar Compute(TScalar a, TScalar b, TScalar c) { return ( a + b ) * c; } I could render it's string representation: r = Compute(VerbalScalar("a", 1), VerbalScalar("b", 2), VerbalScalar("c", 3)); Assert.AreEqual(9, r.Value); Assert.AreEqual("(a+b)*c==(1+2)*3", r.History ); C++ operator overloading allowed for substitution of a simple type with a complex self-tracking entity with an internal tree representation of everything happening with the objects. Now i would like to have the same possibility for NET strings, only instead of variable names i would like to see a stack traces of all the places in code which affected a string. And i want it to work with existing code, and existing compiled assemblies. Also i want all this to hook into visual studio debugger, so i could set a breakpoint, and see everything that happened with a string. Which technology would allow this kind of things? I know it sound like an utopia, but I think visual studio code coverage tools actually do the same kind of job while instrumenting the assemblies.

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  • Understanding C++ pointers (when they point to a pointer)

    - by Stephano
    I think I understand references and pointers pretty well. Here is what I (think I) know: int i = 5; //i is a primitive type, the value is 5, i do not know the address. int *ptr; //a pointer to an int. i have no way if knowing the value yet. ptr = &i; //now i have an address for the value of i (called ptr) *ptr = 10; //go get the value stored at ptr and change it to 10 Please feel free to comment or correct these statements. Now I'm trying to make the jump to arrays of pointers. Here is what I do not know: char **char_ptrs = new char *[50]; Node **node_ptrs = new Node *[50]; My understanding is that I have 2 arrays of pointers, one set of pointers to chars and one to nodes. So if I wanted to set the values, I would do something like this: char_ptrs[0] = new char[20]; node_ptrs[0] = new Node; Now I have a pointer, in the 0 position of my array, in each respective array. Again, feel free to comment here if I'm confused. So, what does the ** operator do? Likewise, what is putting a single * next to the instantiation doing (*[50])? (what is that called exactly, instantiation?)

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  • Circumvent c++ null-terminated string frustration

    - by ypnos
    I'm using boost::program_options and it suffers from the same as many other c++ libs, even std itself: It still uses C-style null-terminated strings, because nobody really likes the weak std::string. The method in question is: options_description_easy_init& operator()(const char* name, const value_semantic* s, const char* description); The typical use case is just fine: options.add_options() ("graphical", bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") However, I need the name of the option to be set dynamically. The reason is that in some cases I nead a custom prefix, which is added to the string by my function std::string key(const std::string& k): options.add_options() (key("graphical"), bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") This fails. I could now use c_str() on the std::string but that's evil -- I don't know how long program_options keeps the variable around and if my string is still alive when needed. I could also reserve memory in a buffer etc. and hand in that. The buffer is never freed and it sucks/is evil. Is there anything else I can do to circumvent the C-style string mess in this situation?

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  • useer degined Copy ctor, and copy-ctors further down the chain - compiler bug ? programers brainbug

    - by J.Colmsee
    Hi. i have a little problem, and I am not sure if it's a compiler bug, or stupidity on my side. I have this struct : struct BulletFXData { int time_next_fx_counter; int next_fx_steps; Particle particles[2];//this is the interesting one ParticleManager::ParticleId particle_id[2]; }; The member "Particle particles[2]" has a self-made kind of smart-ptr in it (resource-counted texture-class). this smart-pointer has a default constructor, that initializes to the ptr to 0 (but that is not important) I also have another struct, containing the BulletFXData struct : struct BulletFX { BulletFXData data; BulletFXRenderFunPtr render_fun_ptr; BulletFXUpdateFunPtr update_fun_ptr; BulletFXExplosionFunPtr explode_fun_ptr; BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr; BulletFX( BulletFXData data, BulletFXRenderFunPtr render_fun_ptr, BulletFXUpdateFunPtr update_fun_ptr, BulletFXExplosionFunPtr explode_fun_ptr, BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr) :data(data), render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } /* //USER DEFINED copy-ctor. if it's defined things go crazy BulletFX(const BulletFX& rhs) :data(data),//this line of code seems to do a plain memory-copy without calling the right ctors render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } */ }; If i use the user-defined copy-ctor my smart-pointer class goes crazy, and it seems that calling the CopyCtor / assignment operator aren't called as they should. So - does this all make sense ? it seems as if my own copy-ctor of struct BulletFX should do exactly what the compiler-generated would, but it seems to forget to call the right constructors down the chain. compiler bug ? me being stupid ? Sorry about the big code, some small example could have illustrated too. but often you guys ask for the real code, so well - here it is :D

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  • How do you calculate div and mod of floating point numbers?

    - by boost
    In Perl, the % operator seems to assume integers. For instance: sub foo { my $n1 = shift; my $n2 = shift; print "perl's mod=" . $n1 % $n2, "\n"; my $res = $n1 / $n2; my $t = int($res); print "my div=$t", "\n"; $res = $res - $t; $res = $res * $n2; print "my mod=" . $res . "\n\n"; } foo( 3044.952963, 7.1 ); foo( 3044.952963, -7.1 ); foo( -3044.952963, 7.1 ); foo( -3044.952963, -7.1 ); gives perl's mod=6 my div=428 my mod=6.15296300000033 perl's mod=-1 my div=-428 my mod=6.15296300000033 perl's mod=1 my div=-428 my mod=-6.15296300000033 perl's mod=-6 my div=428 my mod=-6.15296300000033 Now as you can see, I've come up with a "solution" already for calculating div and mod. However, what I don't understand is what effect the sign of each argument should have on the result. Wouldn't the div always be positive, being the number of times n2 fits into n1? How's the arithmetic supposed to work in this situation?

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  • Sencha 2 : Sync models with hasMany associations in LocalStorage

    - by Alytrem
    After hours and hours trying to do this, I need your help. I have to models : Project and Task. A project hasMany tasks and a task belong to a project. Everyting works well if you don't use a store to save these models. I want to save both tasks and projects in two stores (TaskStore and ProjectStore). These stores use a LocalStorage proxy. I tried many things, and the most logical is : Ext.define('MyApp.model.Task', { extend: 'Ext.data.Model', config: { fields: [ { name: 'name', type: 'string' }, { dateFormat: 'd/m/Y g:i', name: 'start', type: 'date' }, { dateFormat: 'd/m/Y g:i', name: 'end', type: 'date' }, { name: 'status', type: 'string' } ], belongsTo: { model: 'MyApp.model.Project' } } }); Ext.define('MyApp.model.Project', { extend: 'Ext.data.Model', alias: 'model.Project', config: { hasMany: { associationKey: 'tasks', model: 'MyApp.model.Task', autoLoad: true, foreignKey: 'project_id', name: 'tasks', store: {storeId: "TaskStore"} }, fields: [ { name: 'name', type: 'string' }, { dateFormat: 'd/m/Y', name: 'start', type: 'date' }, { dateFormat: 'd/m/Y', name: 'end', type: 'date' } ] } }); This is my "main" : var project = Ext.create("MyApp.model.Project", {name: "mojo", start: "17/03/2011", end: "17/03/2012", status: "termine"}); var task = Ext.create("MyApp.model.Task", {name: "todo", start: "17/03/2011 10:00", end: "17/03/2012 19:00", status: "termine"}); project.tasks().add(task); Ext.getStore("ProjectStore").add(project); The project is added to the store, but task is not. Why ?!

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  • Issue with GCD and too many threads

    - by dariaa
    I have an image loader class which provided with NSURL loads and image from the web and executes completion block. Code is actually quite simple - (void)downloadImageWithURL:(NSString *)URLString completion:(BELoadImageCompletionBlock)completion { dispatch_async(_queue, ^{ // dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ UIImage *image = nil; NSURL *URL = [NSURL URLWithString:URLString]; if (URL) { image = [UIImage imageWithData:[NSData dataWithContentsOfURL:URL]]; } dispatch_async(dispatch_get_main_queue(), ^{ completion(image, URLString); }); }); } When I replace dispatch_async(_queue, ^{ with commented out dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ Images are loading much faster, wich is quite logical (before that images would be loaded one at a time, now a bunch of them are loading simultaneously). My issue is that I have perhaps 50 images and I call downloadImageWithURL:completion: method for all of them and when I use global queue instead of _queue my app eventually crashes and I see there are 85+ threads. Can the problem be that my calling dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0) 50 times in a row makes GCD create too many threads? I thought that gcd handles all the treading and makes sure the number of threads is not huge, but if it's not the case is there any way I can influence number of threads?

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  • How can I override list methods to do vector addition and subtraction in python?

    - by Bobble
    I originally implemented this as a wrapper class around a list, but I was annoyed by the number of operator() methods I needed to provide, so I had a go at simply subclassing list. This is my test code: class CleverList(list): def __add__(self, other): copy = self[:] for i in range(len(self)): copy[i] += other[i] return copy def __sub__(self, other): copy = self[:] for i in range(len(self)): copy[i] -= other[i] return copy def __iadd__(self, other): for i in range(len(self)): self[i] += other[i] return self def __isub__(self, other): for i in range(len(self)): self[i] -= other[i] return self a = CleverList([0, 1]) b = CleverList([3, 4]) print('CleverList does vector arith: a, b, a+b, a-b = ', a, b, a+b, a-b) c = a[:] print('clone test: e = a[:]: a, e = ', a, c) c += a print('OOPS: augmented addition: c += a: a, c = ', a, c) c -= b print('OOPS: augmented subtraction: c -= b: b, c, a = ', b, c, a) Normal addition and subtraction work in the expected manner, but there are problems with the augmented addition and subtraction. Here is the output: >>> CleverList does vector arith: a, b, a+b, a-b = [0, 1] [3, 4] [3, 5] [-3, -3] clone test: e = a[:]: a, e = [0, 1] [0, 1] OOPS: augmented addition: c += a: a, c = [0, 1] [0, 1, 0, 1] Traceback (most recent call last): File "/home/bob/Documents/Python/listTest.py", line 35, in <module> c -= b TypeError: unsupported operand type(s) for -=: 'list' and 'CleverList' >>> Is there a neat and simple way to get augmented operators working in this example?

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  • optimize output value using a class and public member

    - by wiso
    Suppose you have a function, and you call it a lot of times, every time the function return a big object. I've optimized the problem using a functor that return void, and store the returning value in a public member: #include <vector> const int N = 100; std::vector<double> fun(const std::vector<double> & v, const int n) { std::vector<double> output = v; output[n] *= output[n]; return output; } class F { public: F() : output(N) {}; std::vector<double> output; void operator()(const std::vector<double> & v, const int n) { output = v; output[n] *= n; } }; int main() { std::vector<double> start(N,10.); std::vector<double> end(N); double a; // first solution for (unsigned long int i = 0; i != 10000000; ++i) a = fun(start, 2)[3]; // second solution F f; for (unsigned long int i = 0; i != 10000000; ++i) { f(start, 2); a = f.output[3]; } } Yes, I can use inline or optimize in an other way this problem, but here I want to stress on this problem: with the functor I declare and construct the output variable output only one time, using the function I do that every time it is called. The second solution is two time faster than the first with g++ -O1 or g++ -O2. What do you think about it, is it an ugly optimization?

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  • Click behaviour - Difference in IE and FF ?!

    - by OlliD
    Hey folks, i just came to the conclusion that a project i am currently working on might have a "logical" error in functionality. Currently I'am using server technology with PHP/MySQL and JQuery. Within the page there's a normal link reference with tag <a href="contentpage?page=xxx">next step</a> The pain point now seems to be the given jquery click event on the same element. The intension was to save the (current) content of the page (- form elements) via another php script using the php session command. For any reason, IE can handle the click event of Jquery right before executing the standard html command, that reloads the current page again with the new page parameter. By using FF the behaviour is different. I assume, that FF first execute the html command and afterwards execute the javascript code which handles the click event. Therefore the resultset here is wrong respectivly empty. My question now is whether you made the same experience and how you handled / wordarrounded this problem. I'd be thankful fur any of your tips or further feedback. Maybe you also have a solution on how to rethink about the current architecture. Regards, Oliver

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  • Help with this compile error

    - by Scott
    I just picked up an old project and I'm not sure what the following error could mean. g++ -o BufferedReader.o -c -g -Wall -std=c++0x -I/usr/include/xmms2 -Ijsoncpp/include/json/ -fopenmp -I/usr/include/ImageMagick -I/usr/include/xmms2 -I/usr/include/libvisual-0.4 -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -DQT_CORE_LIB -DQT_GUI_LIB -DQT_SCRIPT_LIB -DQT_SHARED -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include/QtScript BufferedReader.cpp In file included from BufferedReader.cpp:23: /usr/include/string.h:36:42: error: missing binary operator before token "(" In file included from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/cwchar:47, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/bits/postypes.h:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/iosfwd:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/ios:39, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/istream:40, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/sstream:39, from BufferedReader.cpp:24: At line 24 of BufferedReader.cpp is #include <string.h>. I've tried it with just <string> but get the same thing. Any clue? Here's the snippet of code from string.h /* Tell the caller that we provide correct C++ prototypes. */ #if defined __cplusplus && __GNUC_PREREQ (4, 4) //line 36 # define __CORRECT_ISO_CPP_STRING_H_PROTO #endif Does that mean __GNUC_PREREQ isn't defined?

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  • How to take a collection of bytes and pull typed values out of it?

    - by Pat
    Say I have a collection of bytes var bytes = new byte[] {0, 1, 2, 3, 4, 5, 6, 7}; and I want to pull out a defined value from the bytes as a managed type, e.g. a ushort. What is a simple way to define what types reside at what location in the collection and pull out those values? One (ugly) way is to use System.BitConverter and a Queue or byte[] with an index and simply iterate through, e.g.: int index = 0; ushort first = System.BitConverter.ToUint16(bytes, index); index += 2; // size of a ushort int second = System.BitConverter.ToInt32(bytes, index); index += 4; ... This method gets very, very tedious when you deal with a lot of these structures! I know that there is the System.Runtime.InteropServices.StructLayoutAttribute which allows me to define the locations of types inside a struct or class, but there doesn't seem to be a way to import the collection of bytes into that struct. If I could somehow overlay the struct on the collection of bytes and pull out the values, that would be ideal. E.g. Foo foo = (Foo)bytes; // doesn't work because I'd need to implement the implicit operator ushort first = foo.first; int second = foo.second; ... [StructLayout(LayoutKind.Explicit, Size=FOO_SIZE)] public struct Foo { [FieldOffset(0)] public ushort first; [FieldOffset(2)] public int second; } Any thoughts on how to achieve this?

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  • Parse files in directory/insert in database

    - by jakesankey
    Hey there, Here is my dillema... I have a directory full of .txt comma delimited files arranged as shown below. What I want to do is to import each of these into a SQL or SQLite database, appending each one below the last. (1 table)... I am open to C# or VB scripting and just not sure how to accomplish this. I want to only extract and import the data starting BELOW the 'Feat. Type,Feat. Name, etc' line. These are stored in a \mynetwork\directory\stats folder on my network drive. Ideally I will be able to add functionality that will make the software/script know not to re-add the file to the database once it has already done so as well. Any guidance or tips is appreciated! $$ SAMPLE= $$ FIXTURE=- $$ OPERATOR=- $$ INSPECTION PROCESS=CMM #4 $$ PROCESS OPERATION=- $$ PROCESS SEQUENCE=- $$ TRIAL=- Feat. Type,Feat. Name,Value,Actual,Nominal,Dev.,Tol-,Tol+,Out of Tol.,Comment Point,_FF_PLN_A_1,X,-17.445,-17.445,0.000,-999.000,999.000,, Point,_FF_PLN_A_1,Y,-195.502,-195.502,0.000,-999.000,999.000,, Point,_FF_PLN_A_1,Z,32.867,33.500,-0.633,-0.800,0.800,, Point,_FF_PLN_A_2,X,-73.908,-73.908,0.000,-999.000,999.000,, Point,_FF_PLN_A_2,Y,-157.957,-157.957,0.000,-999.000,999.000,, Point,_FF_PLN_A_2,Z,32.792,33.500,-0.708,-0.800,0.800,, Point,_FF_PLN_A_3,X,-100.180,-100.180,0.000,-999.000,999.000,, Point,_FF_PLN_A_3,Y,-142.797,-142.797,0.000,-999.000,999.000,, Point,_FF_PLN_A_3,Z,32.768,33.500,-0.732,-0.800,0.800,, Point,_FF_PLN_A_4,X,-160.945,-160.945,0.000,-999.000,999.000,, Point,_FF_PLN_A_4,Y,-112.705,-112.705,0.000,-999.000,999.000,, Point,_FF_PLN_A_4,Z,32.719,33.500,-0.781,-0.800,0.800,, Point,_FF_PLN_A_5,X,-158.096,-158.096,0.000,-999.000,999.000,, Point,_FF_PLN_A_5,Y,-73.821,-73.821,0.000,-999.000,999.000,, Point,_FF_PLN_A_5,Z,32.756,33.500,-0.744,-0.800,0.800,, Point,_FF_PLN_A_6,X,-195.670,-195.670,0.000,-999.000,999.000,, Point,_FF_PLN_A_6,Y,-17.375,-17.375,0.000,-999.000,999.000,, Point,_FF_PLN_A_6,Z,32.767,33.500,-0.733,-0.800,0.800,, Point,_FF_PLN_A_7,X,-173.759,-173.759,0.000,-999.000,999.000,, Point,_FF_PLN_A_7,Y,14.876,14.876,0.000,-999.000,999.000,,

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  • A generic C++ library that provides QtConcurrent functionality?

    - by Lucas
    QtConcurrent is awesome. I'll let the Qt docs speak for themselves: QtConcurrent includes functional programming style APIs for parallel list processing, including a MapReduce and FilterReduce implementation for shared-memory (non-distributed) systems, and classes for managing asynchronous computations in GUI applications. For instance, you give QtConcurrent::map() an iterable sequence and a function that accepts items of the type stored in the sequence, and that function is applied to all the items in the collection. This is done in a multi-threaded manner, with a thread pool equal to the number of logical CPU's on the system. There are plenty of other function in QtConcurrent, like filter(), filteredReduced() etc. The standard CompSci map/reduce functions and the like. I'm totally in love with this, but I'm starting work on an OSS project that will not be using the Qt framework. It's a library, and I don't want to force others to depend on such a large framework like Qt. I'm trying to keep external dependencies to a minimum (it's the decent thing to do). I'm looking for a generic C++ framework that provides me with the same/similar high-level primitives that QtConcurrent does. AFAIK boost has nothing like this (I may be wrong though). boost::thread is very low-level compared to what I'm looking for. I know C# has something very similar with their Parallel Extensions so I know this isn't a Qt-only idea. What do you suggest I use?

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  • which is better: a lying copy constructor or a non-standard one?

    - by PaulH
    I have a C++ class that contains a non-copyable handle. The class, however, must have a copy constructor. So, I've implemented one that transfers ownership of the handle to the new object (as below) class Foo { public: Foo() : h_( INVALID_HANDLE_VALUE ) { }; // transfer the handle to the new instance Foo( const Foo& other ) : h_( other.Detach() ) { }; ~Foo() { if( INVALID_HANDLE_VALUE != h_ ) CloseHandle( h_ ); }; // other interesting functions... private: /// disallow assignment const Foo& operator=( const Foo& ); HANDLE Detach() const { HANDLE h = h_; h_ = INVALID_HANDLE_VALUE; return h; }; /// a non-copyable handle mutable HANDLE h_; }; // class Foo My problem is that the standard copy constructor takes a const-reference and I'm modifying that reference. So, I'd like to know which is better (and why): a non-standard copy constructor: Foo( Foo& other ); a copy-constructor that 'lies': Foo( const Foo& other ); Thanks, PaulH

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  • C++ variable to const expression

    - by user1344784
    template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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  • Error in bisection method code in Matlab

    - by Amanda Collins
    I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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  • c# STILL returning wrong number of cores

    - by Justin
    Ok, so I posted in In C# GetEnvironmentVariable("NUMBER_OF_PROCESSORS") returns the wrong number asking about how to get the correct number of cores in C#. Some helpful people directed me to a couple of questions where similar questions were asked but I have already tried those solutions. My question was then closed as being the same as another question, which is true, it is, but the solution given there didn't work. So I'm opening another one hoping that someone may be able to help realising that the other solutions DID NOT work. That question was How to find the Number of CPU Cores via .NET/C#? which used WMI to try to get the correct number of cores. Well, here's the output from the code given there: Number Of Cores: 32 Number Of Logical Processors: 32 Number Of Physical Processors: 4 As per my last question, the machine is a 64 core AMD Opteron 6276 (4x16 cores) running Windows Server 2008 R2 HPC edition. Regardless of what I do Windows always seems to return 32 cores even though 64 are available. I have confirmed the machine is only using 32 and if I hardcode 64 cores, then the machine uses all of them. I'm wondering if there might be an issue with the way the AMD CPUs are detected. FYI, in case you haven't read the last question, if I type echo %NUMBER_OF_PROCESSORS" at the command line, it returns 64. It just won't do it in a programming environment. Thanks, Justin UPDATE: Outputting PROCESSOR_ARCHITECTURE returns AMD64 from the command line, but x86 from the program. The program is 32-bit running on 64-bit hardware. I was asked to compile it to 64-bit but it still shows 32 cores.

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  • Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

    - by volnet
    #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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  • Determine if a Range contains a value

    - by Brad Dwyer
    I'm trying to figure out a way to determine if a value falls within a Range in Swift. Basically what I'm trying to do is adapt one of the examples switch statement examples to do something like this: let point = (1, -1) switch point { case let (x, y) where (0..5).contains(x): println("(\(x), \(y)) has an x val between 0 and 5.") default: println("This point has an x val outside 0 and 5.") } As far as I can tell, there isn't any built in way to do what my imaginary .contains method above does. So I tried to extend the Range class. I ended up running into issues with generics though. I can't extend Range<Int> so I had to try to extend Range itself. The closest I got was this but it doesn't work since >= and <= aren't defined for ForwardIndex extension Range { func contains(val:ForwardIndex) -> Bool { return val >= self.startIndex && val <= self.endIndex } } How would I go about adding a .contains method to Range? Or is there a better way to determine whether a value falls within a range? Edit2: This seems to work to extend Range extension Range { func contains(val:T) -> Bool { for x in self { if(x == val) { return true } } return false } } var a = 0..5 a.contains(3) // true a.contains(6) // false a.contains(-5) // false I am very interested in the ~= operator mentioned below though; looking into that now.

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  • Freeing ImageData when deleting a Canvas

    - by user578770
    I'm writing a XUL application using HTML Canvas to display Bitmap images. I'm generating ImageDatas and imporingt them in a canvas using the putImageData function : for(var pageIndex=0;pageIndex<100;pageIndex++){ this.img = imageDatas[pageIndex]; /* Create the Canvas element */ var imgCanvasTmp = document.createElementNS("http://www.w3.org/1999/xhtml",'html:canvas'); imgCanvasTmp.setAttribute('width', this.img.width); imgCanvasTmp.setAttribute('height', this.img.height); /* Import the image into the Canvas */ imgCanvasTmp.getContext('2d').putImageData(this.img, 0, 0); /* Use the Canvas into another part of the program (Commented out for testing) */ // this.displayCanvas(imgCanvasTmp,pageIndex); } The images are well imported but there seems to be a memory leak due to the putImageData function. When exiting the "for" loop, I would expect the memory allocated for the Canvas to be freed but, by executing the code without executing putImageData, I noticed that my program at the end use 100Mb less (my images are quite big). I came to the conclusion that the putImageData function prevent the garbage collector to free the allocated memory. Do you have any idea how I could force the garbage collector to free the memory? Is there any way to empty the Canvas? I already tried to delete the canvas using the delete operator or to use the clearRect function but it did nothing. I also tried to reuse the same canvas to display the image at each iteration but the amount of memory used did not changed, as if the image where imported without deleting the existing ones...

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  • Passing functor and function pointers interchangeably using a templated method in C++

    - by metroxylon
    I currently have a templated class, with a templated method. Works great with functors, but having trouble compiling for functions. Foo.h template <typename T> class Foo { public: // Constructor, destructor, etc... template <typename Func> void bar(T x, Func f); }; template <typename T> template <typename Func> Foo::bar(T x, Func f) { /* some code here */ } Main.cpp #include "Foo.h" template <typename T> class Functor { public: Functor() {} void operator()(T x) { /* ... */ } private: /* some attributes here */ }; void Function(T x) { /* ... */ } int main() { Foo<int> foo; foo.bar(2, Functor); // No problem foo.bar(2, Function); // <unresolved overloaded function type> return 0; }

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  • How would I compare two Lists(Of <CustomClass>) in VB?

    - by Kumba
    I'm working on implementing the equality operator = for a custom class of mine. The class has one property, Value, which is itself a List(Of OtherClass), where OtherClass is yet another custom class in my project. I've already implemented the IComparer, IComparable, IEqualityComparer, and IEquatable interfaces, the operators =, <>, bool and not, and overriden Equals and GetHashCode for OtherClass. This should give me all the tools I need to compare these objects, and various tests comparing two singular instances of these objects so far checks out. However, I'm not sure how to approach this when they are in a List. I don't care about the list order. Given: Dim x As New List(Of OtherClass) From {New OtherClass("foo"), New OtherClass("bar"), New OtherClass("baz")} Dim y As New List(Of OtherClass) From {New OtherClass("baz"), New OtherClass("foo"), New OtherClass("bar")} Then (x = y).ToString should print out True. I need to compare the same (not distinct) set of objects in this list. The list shouldn't support dupes of OtherClass, but I'll have to figure out how to add that in later as an exception. Not interested in using LINQ. It looks nice, but in the few examples I've played with, adds a performance overhead in that bugs me. Loops are ugly, but they are fast :) A straight code answer is fine, but I'd like to understand the logic needed for such a comparison as well. I'm probably going to have to implement said logic more than a few times down the road.

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