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  • A question on vectors, pointers and iterators

    - by xbonez
    Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated. Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions: what type is p? what type is *p? what code provides the address of the actual Thingie? what code provides the actual Thingie?

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  • .save puts NULL in id field in Rails

    - by mathee
    Here's the model file: class ProfileTag < ActiveRecord::Base def self.create_or_update(options = {}) id = options.delete(:id) record = find_by_id(id) || new record.id = id record.attributes = options puts "record.profile_id is" puts record.profile_id record.save! record end end This gives me the correct print out in my log. But it also says that there's a call to UPDATE that sets profile_id to NULL. Here's some of the output in the log file: Processing ProfilesController#update (for 127.0.0.1 at 2010-05-28 18:20:54) [PUT] Parameter: {"commit"=>"Save", ...} ?[4;36;1mProfileTag Create (0.0ms)?[0m ?[0;1mINSERT INTO `profile_tags` (`reputation_value`, `updated_at`, `tag_id`, `id`, `profile_id`, `created_at`) VALUES(0, '2010-05-29 01:20:54', 1, NULL, 4, '2010-05-29 01:20:54')?[0m ?[4;35;1mSQL (2.0ms)?[0m ?[0mCOMMIT?[0m ?[4;36;1mSQL (0.0ms)?[0m ?[0;1mBEGIN?[0m ?[4;35;1mSQL (0.0ms)?[0m ?[0mCOMMIT?[0m ?[4;36;1mProfileTag Load (0.0ms)?[0m ?[0;1mSELECT * FROM `profile_tags` WHERE (`profile_tags`.profile_id = 4) ?[0m ?[4;35;1mSQL (1.0ms)?[0m ?[0mBEGIN?[0m ?[4;36;1mProfileTag Update (0.0ms)?[0m ?[0;1mUPDATE `profile_tags` SET profile_id = NULL WHERE (profile_id = 4 AND id IN (35)) ?[0m I'm not sure I understand why the INSERT puts the value into profile_id properly, but then it sets it to NULL on an UPDATE. If you need more specifics, please let me know. I'm thinking that the save functionality does many things other than INSERTs into the database, but I don't know what I need to specify so that it will properly set profile_id.

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  • Array of pointers in Objective-C using NSArray

    - by Amir
    Hello, I am writting program for my iphone and have a qestion. lets say i have class named my_obj class my_obj { NSString *name; NSinteger *id; NSinteger *foo; NSString *boo; } now i allocate 100 objects from type my_obj and insert them to array from type NSArray. then i want to sort the Array in two different ways. one by the name and the second by the id. i want to allocate another two arrays from type NSArray *arraySortByName *arraySortById what i need to do if i just want the sorted arrays to be referenced to the original array so i will get two sorted arrays that point to the original array (that didnt changed!) i other word i dont want to allocate another 100 objects to each sorted array.

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  • Unable to free const pointers in C

    - by lego69
    How can I free a const char*? I allocated new memory using malloc, and when I'm trying to free it I always receive the error "incompatible pointer type" The code that causes this is something like: char* name="Arnold"; const char* str=(const char*)malloc(strlen(name)+1); free(str); // error here

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  • Embedding Python and adding C functions to the interpreter

    - by monoceres
    I'm currently writing an applications that embedds the python interpreter. The idea is to have the program call user specified scripts on certain events in the program. I managed this part but now I want the scripts to be able to call functions in my program. Here's my code so far: #include "python.h" static PyObject* myTest(PyObject* self,PyObject *args) { return Py_BuildValue("s","123456789"); } static PyMethodDef myMethods[] = {{"myTest",myTest},{NULL,NULL}}; int main() { Py_Initialize(); Py_InitModule("PROGRAM",myMethods); PyRun_SimpleString("print PROGRAM.myTest()"); Py_Finalize(); } Thanks!

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  • Apples, oranges, and pointers to the most derived c++ class

    - by Matthew Lowe
    Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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  • Setting pointers to structs

    - by Bobby
    I have the following struct: struct Datastore_T { Partition_Datastores_T cmtDatastores; // bytes 0 to 499 Partition_Datastores_T cdhDatastores; // bytes 500 to 999 Partition_Datastores_T gncDatastores; // bytes 1000 to 1499 Partition_Datastores_T inpDatastores; // bytes 1500 1999 Partition_Datastores_T outDatastores; // bytes 2000 to 2499 Partition_Datastores_T tmlDatastores; // bytes 2500 to 2999 Partition_Datastores_T sm_Datastores; // bytes 3000 to 3499 }; I want to set a char* to struct of this type like so: struct Datastore_T datastores; // Elided: datastores is initialized with data here char* DatastoreStartAddr = (char*)&datastores; memset(DatastoreStartAddr, 0, 3500); The problem I have is that DatastoreStartAddr always has a value of zero when it should point to the struct that has been initialized with data. What am I doing wrong?

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  • Nhibernate:null index column for collection Error

    - by Quintin Par
    I am working a subsonic to NH migration(I can’t change the schema) and while creating the mapping I came across this error null index column for collection: Company.Core.CompanyUser.Addresses My mapping from the User side is mapping.HasMany(x => x.Addresses).AsList().KeyColumn("user_id").Cascade.All().Inverse(); xml <list cascade="all" inverse="true" name="Addresses"> <key> <column name="user_id" /> </key> <index /> <one-to-many class="Company.Core.CompanyAddress, Company.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </list> On the Address side it is mapping.CompositeId().KeyReference(x => x.User, "user_id").KeyProperty(x => x.Type); xml <composite-id mapped="false" unsaved-value="undefined"> <key-property name="Type" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Type" /> </key-property> <key-many-to-one name="User" class="Company.Core.CompanyUser, Company.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"> <column name="user_id" /> </key-many-to-one> </composite-id> When I try to load this collection as user.Addresses I get the index null exception. How do I fix this error?

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  • Seg Fault with malloc'd pointers

    - by anon
    I'm making a thread class to use as a wrapper for pthreads. I have a Queue class to use as a queue, but I'm having trouble with it. It seems to allocate and fill the queue struct fine, but when I try to get the data from it, it Seg. faults. http://pastebin.com/Bquqzxt0 (the printf's are for debugging, both throw seg faults) edit: the queue is stored in a dynamically allocated "struct queueset" array as a pointer to the data and an index for the data

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  • Checkboxes in ADF are initially null, where I want them to be 0

    - by Mark Tielemans
    I am using ADF in JDeveloper and don´t have any experience with either of the two. Now I´ve run into quite some trouble yet, but for this particular thing I decided to consult the wisom of stackoverflow. The thing is, I have an edit form for an object that contains 3 checkboxes. The checked values are set to 1, unchecked to 0. In my database, the values are NOT NULL, and I want to keep it that way. The thing is, in the edit form, if the user submits the form leaving any boxes unchecked, it will result in an error, because the unchecked box values apparently remain null. Only after checking and then unchecking the boxes again, their values will be '0' rather than null. I've tried some things, including making the attributes mandatory in the domain BCD, but that just gives a bit more neat error message.. Any help would be greatly appreciated!! EDIT I made a little progress thanks to the guide provided by Joe, but still run into problems. I changed the values that should be checkboxes in my model, making them BOOLEANs where the table columns are NUMBERs (All are also mandatory and have a default value of 0). This automatically changed the corresponding View Object too. In the Application module, this now works great. It shows checkboxes, a checked one will return 1, an untouched one will return 0. However, I deleted the old form, and inserted a new one using the corresponding Data Control. I gave these values the checkbox type. I still had to edit the bindings (which I think reflects the problem, as this is not the case with, say, a model-level defined LOV) and gave them 1 for checked and 0 for unchecked. However, now apart from the original problem still occurring, also the checkboxes cannot be unchecked after checking, and return 0 when checked (and null when left untouched). Even though this has created new problems, it works correctly in my AM. Does someone know what I'm doing wrong in my Swing form?

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  • Prob comparing pointers and integer in C

    - by Dimitri
    Hi I have a problem with this code. When i am using this function I have no warnings. : void handler(int sig){ switch(sig) { case SIGINT : { click++; fprintf(stdout,"SIGINT recu\n"); if( click == N){ exit(0); } } case SIGALRM : fprintf(stdout,"SIGALRM received\n"); exit(0); case SIGTERM: fprintf(stdout,"SIGTERM received\n"); exit(0); } } But when i rewrite the function with this new version, I have a " comparison between pointer and integer" warning on the if statement: void handler( int sig){ printf("Signal recu\n"); if( signal == SIGINT){ click++; fprintf(stdout,"SIGINT received; Click = %d\n",click); if(click == N){ fprintf(stdout,"Exiting with SIGINT\n"); exit(0); } } else if(signal == SIGALRM){ fprintf(stdout,"SIGALRM received\n"); exit(0); } else if(signal == SIGTERM){ fprintf(stdout,"SIGTERM received\n"); exit(0); } Can someone tell me where is the prob?

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  • C++ Pointers to functions.

    - by Andy Leman
    using namespace std; int addition (int a, int b) { return (a+b); } int subtraction (int a, int b) { return (a-b); } int operation (int x, int y, int (*functocall)(int,int)) { int g; g = (*functocall)(x,y); return(g); } int main() { int m,n; int (*minus)(int,int) = subtraction; m = operation (7,5,addition); n = operation (20,m,minus); cout << n; return 0; } Can anybody explain this line for me int (*minus)(int,int) = subtraction; Thanks a lot!

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  • C++ class with char pointers returning garbage

    - by JMP
    I created a class "Entry" to handle Dictionary entries, but in my main(), I create the Entry() and try to cout the char typed public members, but I get garbage. When I look at the Watch list in debugger, I see the values being set, but as soon as I access the values, there is garbage. Can anyone elaborate on what I might be missing? #include <iostream> using namespace std; class Entry { public: Entry(const char *line); char *Word; char *Definition; }; Entry::Entry(const char *line) { char tmp[100]; strcpy(tmp, line); Word = strtok(tmp, ",") + '\0'; Definition = strtok(0,",") + '\0'; } int main() { Entry *e = new Entry("drink,What you need after a long day's work"); cout << "Word: " << e->Word << endl; cout << "Def: " << e->Definition << endl; cout << endl; delete e; e = 0; return 0; }

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  • Segmentation fault on returning from main (very short and simple code, no arrays or pointers)

    - by Gábor Kovács
    I've been wondering why the following trivial code produces a segmentation fault when returning from main(): //Produces "Error while dumping state (probably corrupted stack); Segmentation fault" #include <iostream> #include <fstream> #include <vector> using namespace std; class Test { vector<int> numbers; }; int main() { Test a; ifstream infile; cout << "Last statement..." << endl; // this gets executed return 0; } Interestingly, 1) if only one of the two variables is declared, I don't get the error, 2) if I declare a vector variable instead of an object with a vector member, everything's fine, 3) if I declare an ofstream instead of an ifstream, again, everything works fine. Something appears to be wrong with this specific combination... Could this be a compiler bug? I use gcc version 3.4.4 with cygwin. Thanks for the tips in advance. Gábor

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  • subscript operator on pointers

    - by Lodle
    If i have a pointer to an object that has an overloaded subscript operator ( [] ) why cant i do this: MyClass *a = new MyClass(); a[1]; but have to do this instead: MyClass *a = new MyClass(); (*a)[1];

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  • Suggestions/pointers for Post/Get to an .ASP (or .ASPX) page from a desktop app

    - by Clay Nichols
    I'm planning to have a desktop app interact with some .ASP or .ASPX pages on a server. I've only done a little bit with .asp pages and I'm thinking I'd just Post or Get a URL with some variables: MySite.com/Functions.asp?FunctionName=?Paramater1=somevalue?Parameter2=... I'm wondering if there is any better way to go about this? Am I missing something? Is there perhaps a better way to go about this?

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  • Declaring an array of character pointers (arg passing)

    - by Isaac Copper
    This is something that should be easy to answer, but is more difficult for me to find a particular right answer on Google or in K&R. I could totally be overlooking this, too, and if so please set me straight! The pertinent code is below: int main(){ char tokens[100][100]; char str = "This is my string"; tokenize(str, tokens); for(int i = 0; i < 100; i++){ printf("%s is a token\n", token[i]); } } void tokenize(char *str, char tokens[][]){ //do stuff with string and tokens, putting //chars into the token array like so: tokens[i][j] = <A CHAR> } So I realize that I can't have char tokens[][] in my tokenize function, but if I put in char **tokens instead, I get a compiler warning. Also, when I try to put a char into my char array with tokens[i][j] = <A CHAR>, I segfault. Where am I going wrong? (And in how many ways... and how can I fix it?) Thanks so much!

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  • Function pointers in javascript using django

    - by Hulk
    Is this a valid function pointer code below, In views , def change(request): dict={} function_ptr="create()" dict.update({'function_ptr' : function_ptr}) return render_to_response('mpjt/create.html',context_instance=RequestContext(request,{'dict': dict})) In create.html $(document).ready(function() { var a = '{{dict.function_ptr}}' func_ptr(a); function create() { alert('got respponse'); } }); Thanks..

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  • Arry of pointers in objective c using NSArray

    - by Amir
    Hello, I am writting program for my iphone and have a qestion. lets say i have class named my_obj class my_obj { NSString *name; NSinteger *id; NSinteger *foo; NSString *boo; } now i allocate 100 objects from type my_obj and insert them to array from type NSArray. then i want to sort the Array in two different ways. one by the name and the second by the id. i want to allocate another two arrays from type NSArray *arraySortByName *arraySortById what i need to do if i just want the sorted arrays to be referenced to the original array so i will get two sorted arrays that point to the original array (that didnt changed!) i other word i dont want to allocate another 100 objects to each sorted array.

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  • hibernate empty collection in component

    - by Jurgen H
    I have a component mapped using Hibernate. If all fields in the component in the database are null, the component itself is set to null by hibernate. This is the expected behavior and also what I need. The problem I have, is that when I add a bag to that component, the bag is initialized to an empty list. This means the component has a non null value... resulting in the component being created. Any idea how to fix this? <class name="foo.bar.Entity" table="Entity"> <id name="id" column="id"> <generator class="native" /> </id> <property name="departure" column="departure_time" /> <property name="arrival" column="arrival_time" /> <component name="statistics"> <bag name="linkStatistics" lazy="false" cascade="all" > <key column="entity_id" not-null="true" /> <one-to-many class="foo.bar.LinkStatistics" /> </bag> <property name="loggedTime" column="logged_time" /> ... </component> A criteria with Restirctions.isNull("statistics") does return the expected values.

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  • Question about C Pointers (just learning)

    - by Mike
    I am curious as to why this is an error and what the error message means. Here is some code. int *x[] = {"foo", "bar", "baz"}; int *y[] = {"foo", "bar", "baz"}; x = y; I try to compile and I get this: error: incompatible types when assigning to type ‘char [3]’ from type ‘char *’ Question #1 why is this an error? and Question #2 why are the types different? Thanks for you help.

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