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  • How to reload a tableView i.e call the viewDidLoad method if a condition is met

    - by Kquane Ingram
    The problem is this i need a way to basically erase all the entry data a user placed into my arrays if a condition is met. Im new to Objective-C and iOS programming, but i believed the solution might be in calling the viewDidLoad method, thus it would virtually refresh the applications with the values of the array reset to default. If there is any other logical way of doing this i would appreciate the help. In short i need to refresh the arrays as they were when the application first launched and the user did not select anything. This is the part where i need it to refresh. if ([gradeRecieved objectAtIndex:i]==nil) { break; // if this condition is met the program must begin anew. Edit* I need to recall the - (void)viewDidLoad method here is more of the code. -(IBAction)button:(id)sender{ int i = 0; int sum = 0; int gradeEarned; int creditHours = 3; for ( i=0;i<8 ; i++) { if ([[points objectAtIndex:i] tag]==GradeA.intValue) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeA]; } if ([[points objectAtIndex:i]tag]==GradeB.intValue) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeB]; } if ([[points objectAtIndex:i]tag]==GradeC.intValue){ [gradeRecieved replaceObjectAtIndex:i withObject:GradeC]; } if ([gradeRecieved objectAtIndex:i]==nil) { break; // if this condition is met the program must restart. } } while ( i<[gradeRecieved count]) { if ([gradeRecieved objectAtIndex:i] == GradeA ) { [finArray replaceObjectAtIndex:i withObject:GradeA]; i++; continue; } if ([gradeRecieved objectAtIndex:i] == GradeB ) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeB]; i++; continue; } if ([gradeRecieved objectAtIndex:i] == GradeC ) { [gradeRecieved replaceObjectAtIndex:i withObject:GradeC]; i++; continue; } }

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Does Socket open another thread? Does it return something?

    - by Roman
    In the client application I call new Socket(serverIP,serverPort). As a result the client application sends a request to the server application to open a socket. Does it start a new thread? I mean which of the following is true? Client application sends a request and immediately starts to execute following commands (not weighting for the answer). Client sends the request and weights for the answer. As soon as the answer is obtained, the client application continues to execute following commands. The second case seems to be more realistic and logical for me. However, I do not understand what happens if the server does not open a socket and it does not say that it does not "want" to open the second (it can happen if the server does not exist or network is broken). What will happen in this case? Will server weight forever? In general it would be nice for the client to know what is the result of its request for the socket. For example I can imagine the following situations: The socket is opened by the server. The server refuses to open a socket. So, server exists, it got the request from the client but it says "no". There is no response from the server. I know that new Socket(serverIP,serverPort) does not "return" this kind of information. But it throws exceptions. One of them is "UnkownHostException". When it is thrown? When the server is not responding for a while (for how long)? ADDED: I just found out that UnknownHostException is thrown to indicate that the IP address of a host could not be determined. So, it is unrelated with the above described situations (server is not responding, server refuses to open a socket).

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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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  • 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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  • 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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  • 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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  • Using git (or some other VCS) at your company

    - by supercheetah
    Some friends of mine and I were talking recently about version control, and how they were using VSS at their jobs, and were probably going to be moving off of that soon. One of them said that his company will likely be going with Team Foundation Server. Eventually, the conversation did get around to talking about some of the open source VCSes out there, including git and SVN. None of us really knew about any companies that use either of these internally, although we imagined that a number of them did so for SVN, but we weren't too sure about git. I brought up Google and Android using it, but my friend figured that's only for the public facing source code, and that they may use something different for internal projects. Apparently it's more than just SCM that makes TFS so intriguing: Microsoft Sales people and support (although my friend did point out somethings to his managers that he thought might be misleading on MS' part) Integration of things beyond SCM, including project management (I'm just finding out that there are geared towards the same things for git) Again, it's Microsoft, and the transition from VSS to TFS seems logical (or does it?) I'm not much of a fan of SVN, so I didn't really bring it up much, but I am curious about whether or not git is used at your company for internal projects. Have you thought about it, and decided against it? Any reason why?

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  • How to iterate properly across a const set?

    - by Jared
    I'm working on a program that's supposed to represent a graph. My issue is in my printAdjacencyList function. Basically, I have a Graph ADT that has a member variable "nodes", which is a map of the nodes of that graph. Each Node has a set of Edge* to the edges it is connected to. I'm trying to iterate across each node in the graph and each edge of a node. void MyGraph::printAdjacencyList() { std::map<std::string, MyNode*>::iterator mit; std::set<MyEdge*>::iterator sit; for (mit = nodes.begin(); mit != nodes.end(); mit++ ) { std::cout << mit->first << ": {"; const std::set<MyEdge*> edges = mit->second->getEdges(); for (sit = edges.begin(); sit != edges.end(); sit++) { std::pair<MyNode*, MyNode*> edgeNodes = *sit->getEndpoints(); } } std::cout << " }" << std::endl; } getEdges is declared as: const std::set<MyEdge*>& getEdges() { return edges; }; and get Endpoints is declared as: const std::pair<MyNode*, MyNode*>& getEndpoints() { return nodes; }; The compiler error I'm getting is: MyGraph.cpp:63: error: request for member `getEndpoints' in `*(&sit)->std::_Rb_tree_const_iterator<_Tp>::operator-> [with _Tp = MyEdge*]()', which is of non-class type `MyEdge* const' MyGraph.cpp:63: warning: unused variable 'edgeNodes' I have figured out that this probably means I'm misusing const somewhere, but I can't figure out where for the life of me. Any information would be appreciated. Thanks!

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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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  • 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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  • Will this cause a problem with different runtimes with DLL?

    - by Milo
    My gui application supports polymorphic timed events so that means that the user calls new, and the gui calls delete. This can create a problem if the runtimes are incompatible. So I was told a proposed solution would be this: class base; class Deallocator { void operator()(base* ptr) { delete ptr; } } class base { public: base(Deallocator dealloc) { m_deleteFunc = dealloc; } ~base() { m_deleteFunc(this); } private: Deallocator m_deleteFunc; } int main { Deallocator deletefunc; base baseObj(deletefunc); } While this is a good solution, it does demand that the user create a Deallocator object which I do not want. I was however wondering if I provided a Deallocator to each derived class: eg class derived : public base { Deallocator dealloc; public: Derived() : base(dealloc); { } }; I think this still does not work though. The constraint is that: The addTimedEvent() function is part of the Widget class which is also in the dll, but it is instanced by the user. The other constraint is that some classes which derive from Widget call this function with their own timed event classes. Given that "he who called new must call delete" what could work given these constraints? Thanks

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