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• What is Ruby's double-colon (::) all about?

  - by Meltemi

  I'd probably be able to answer this for myself if "::" wasn't so hard to Google. Didn't see anything on SO so thought I'd try my luck. What is this double-colon :: all about? I see it everywhere in Rails: class User < ActiveRecord::Base or… ActionController::Routing::Routes.draw do |map| I found a definition from this guy: The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module. but that just leads to more questions. What good is scope (private, protected) if you can just use :: to expose anything?

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• C Class Instance from Void Pointer using Ctypes

  - by g.d.d.c

  I've got a C DLL that exposes a handful of methods that return void pointers to a Class like so: void *GetLicense() { static AppLicenseImpl ipds_; return (void *) &ipds_; } In C++, after loading the DLL, I'd do this to work with it: typedef void *(* FPGetLicense)(); GetLicense_ = (FPGetLicense)GetAddress("GetLicense"); license_ = (AppLicense *) GetLicense_(); license_->GetApplicationStatus(); // Load data so that other calls don't fail I can't figure out how to parallel that in Python. This gets me the pointer: d = ctypes.cdll.LoadLibrary('license.dll') d.GetLicense.restype = ctypes.c_void_p p = d.GetLicense() # returns ptr loc, something like 8791433660848L But I obviously can't call p.GetApplicationStatus() in Python. Does anyone have a suggestion on how I'd instantiate that Class the rest of the way in Python so that I can call GetApplicationStatus()?

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• Error debugging - Conversion from String to Double

  - by Jamie Taylor

  I'm doing some error debugging trying to get the errors on our website down to a minimum and there seems to be an error that is popping up quite a lot Conversion from string "" to type 'Double' is not valid. I'm unable to replicate this problem but I can see that it is happening. I've been looking through the code in one of the pages and strolled across this Dim varWeek As String If varWeek < 10 Then 'Do something' End If Could this be causing the problem as it is trying to see if a String is less than 10 which is an Integer? As I said before as I am unable to see this error in the first place so changing this to an Integer doesn't change anything on my system. Thanks.

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• Double indirection and structures passed into a function

  - by ZPS

  I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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• C++ -malign-double compiler flag

  - by Martin

  I need some help on compiler flags in c++. I'm using a library that is a port to linux from windows, that has to be compiled with the -malign-double flag, "for Win32 compatibility". It's my understanding that this mean I absolutely have to compile my own code with this flag as well? How about other .so shared libraries, do they have be recompiled with this flag as well? If so, is there any way around this? I'm a linux newbie (and c++), so even though I tried to recompile all the libraries I'm using for my project, it was just too complicated to recursively find the source for all the libraries and the libraries they're dependent on, and recompile everything.

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• IIS Active Directory double handshake hickup

  - by AngryHacker

  I have a .net 2.0 click-once application that connects to IIS web services on Windows 2003 R2 64-bits. The IIS is setup with Integrated Windows Authentication. So whenever a web service call is made to IIS web services, there is a double handshake taking place: Client Request #1 GetEmployeeList Server Response #1 <- 401 HTTP/1.1 401 Unauthorized WWW-Authenticate: Negotiate WWW-Authenticate: NTLM Client Request #2 REQUEST Header... Server Response #2 <- 200 Data Received Lately, however, Server Response #1 will sometimes (a good 20 percent of the calls) take a massive amount of time (like 25 to 30 seconds). How do I debug this problem? Is this a Active Directory problem or a Domain Controller problem?

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• Dangling pointer

  - by viswanathan

  Does this piece of code lead to dangling pointer. My guess is no. class Sample { public: int *ptr; Sample(int i) { ptr = new int(i); } ~Sample() { delete ptr; } void PrintVal() { cout << "The value is " << *ptr; } }; void SomeFunc(Sample x) { cout << "Say i am in someFunc " << endl; } int main() { Sample s1 = 10; SomeFunc(s1); s1.PrintVal(); }

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• Building and rendering a bitmap from a double array

  - by Ami

  I'm new to c# and I'm sure I'm missing something simple here. I'm trying to build a bitmap from integer values (0-255) in a double array and then render it in a PictureBox. I think my Bitmap is getting generated but it isn't displaying in my PictureBox. Bitmap bmp = new Bitmap(image_width, image_height); Color pxl_color = new Color(); for (int i = 0; i < image_width; i++) { for (int j = 0; j < image_height; j++) { pxl_color = Color.FromArgb(array_bitmap[i][j]); bmp.SetPixel(i, j, pxl_color); } } PictureBox1.Image = bmp; Thanks in advance.

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• storing an integer constant other than zero in a pointer variable

  - by benjamin button

  int main() { int *d=0; printf("%d\n",*d); return 0; } this works fine. >cc legal.c > ./a.out 0 if i change the statement int *d=0; to int *d=1; i see the error. cc: "legal.c", line 6: error 1522: Cannot initialize a pointer with an integer constant other than zero. so its obvious that it will allow only zero.i want to know what happens inside the memory when we do this int *d=0 which is making it valid syntax. I am just asking this out of curiosity!

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• Avoid incompatible pointer warning when dealing with double-indirection

  - by fnawothnig

  Assuming this program: #include <stdio.h> #include <string.h> static void ring_pool_alloc(void **p, size_t n) { static unsigned char pool[256], i = 0; *p = &pool[i]; i += n; } int main(void) { char *str; ring_pool_alloc(&str, 7); strcpy(str, "foobar"); printf("%s\n", str); return 0; } ... is it possible to somehow avoid the GCC warning test.c:12: warning: passing argument 1 of ‘ring_pool_alloc’ from incompatible pointer type test.c:4: note: expected ‘void **’ but argument is of type ‘char **’ ... without casting to (void**) (or simply disabling the compatibility checks)? Because I would very much like to keep compatibility warnings regarding indirection-level...

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• Void pointer values comparing C++

  - by user2962977

  My actual question is it really possible to compare values contained in two void pointers, when you actually know that these values are the same type? For example int. void compVoids(void *firstVal, void *secondVal){ if (firstVal < secondVal){ cout << "This will not make any sense as this will compare addresses, not values" << endl; } } Actually I need to compare two void pointer values, while outside the function it is known that the type is int. I do not want to use comparison of int inside the function. So this will not work for me as well: if (*(int*)firstVal > *(int*)secondVal) Any suggestions? Thank you very much for help!

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• inode_operations , warning: initialization from incompatible pointer type

  - by djTeller

  Hi everyone, I'm trying to compile a simple Kernel program that read and write from a proc file. I'm trying to set permission to that file by overriding the permission fp in inode_operations struct (.permission) static int module_permission(struct inode *inode, int op, struct nameidata *foo) { . . . } static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; For some reason, when I compile this i get - warning: initialization from incompatible pointer type on the following line: .permission = module_permission, /* check for permissions */ Any idea how to solve this? Thanks!

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• Converting c pointer types

  - by bobbyb

  I have a c pointer to a structre type called uchar4 which looks like { uchar x; uchar y; uchar z; uchar w; } I also have data passed in as uint8*. I'd like to create a uchar* pointing to the data at the uint8* so I've tried doing this: uint8 *data_in; uchar4 *temp = (uchar4*)data_in; However, the first 8 bytes always seem to be wrong. Is there another way of doing this?

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• Object pointer value as key into dictionary

  - by Ranking Stackingblocks

  I want to use the object's reference value as a key into a dictionary, as opposed to a copy of value of the object. So, I essentially want to store an object associated with a particular instance of another object in a dictionary and retrieve that value later. Is this possible? Is it completely against the idea of NSDictionary? I can tell that I am probably approaching this the wrong way because the dictionary wants me to implement NSCopying on the object itself, which doesn't really make sense in terms of what I'm doing. I can see that what I should really be doing is wrapping the pointer value, but that seems a little mad. Advice would be appreciated.

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• relace double quotes to parse JSON in PHP

  - by hunt

  hi, i have following json format { "status": "ACTIVE", "result": false, "isworking": false, "margin": 1, "employee": { "111": { "val1": 5.7000000000000002, "val2": "9/2", "val3": 5.7000000000000002 }, "222": { "val1": 31.550000000000001, "val2": "29/1", "val3": 31.550000000000001 } } } how the problem is when i am trying to decode above json response in php using json_decode($res,true) { true param for associative array } i am getting following result as few fields like "result":false is not "result":"false" i.e. at many of the places doubles quotes are missing in values of json. see in val1 and val3 fields resultant data after decoding in php (associative array) Array ( [status] = ACTIVE [result] = [isworking] = [margin] = 1 [employee] = Array ( [111] = Array ( [val1] = 5.7 [val2] = 9/2 [val3] = 5.7 ) [222] = Array ( [val1] = 31.55 [val2] = 29/1 [val3] = 31.55 ) ) ) please help me on how would i insert double quotes in values ? Thanks

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• Baffled by PHP escaping of double-quotes in HTML forms

  - by rjray

  I have a simple PHP script I use to front-end an SQLite database. It's nothing fancy or complex. But I have noticed from looking at the records in the database that anything I enter in a form-field with double-quotes comes across in the form-processing as though I'd escaped the quotes with a backslash. So when I entered a record with the title: British Light Utility Car 10HP "Tilly" what shows up in the database is: British Light Utility Car 10HP \"Tilly\" I don't know where these are coming from, and what's worse, even using the following preg_replace doesn't seem to remove them: $name = preg_replace('/\\"/', '"', $_REQUEST['kits_name']); If I dump out $name, it still bears the unwanted \ characters.

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• Function template accepting nothing less than a bidirectional iterator or a pointer

  - by san

  I need a function template that accepts two iterators that could be pointers. If the two arguments are random_access iterators I want the return type to be an object of std::iterator<random_access_iterator_tag, ...> type else a std::iterator<bidirectional_iterator_tag, ...> type. I also want the code to refuse compilation if the arguments are neither a bidirectional iterator, nor a pointer. I cannot have dependency on third party libraries e.g. Boost Could you help me with the signature of this function so that it accepts bidirectional iterators as well as pointers, but not say input_iterator, output_iterator, forward_iterators. One partial solution I can think of is the following template<class T> T foo( T iter1, T iter2) { const T tmp1 = reverse_iterator<T>(iter1); const T tmp2 = reverse_iterator<T>(iter2); // do something } The idea is that if it is not bidirectional the compiler will not let me construct a reverse_iterator from it.

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• pointer delegate in STL set.

  - by ananth

  hi. Im kinda stuck with using a set with a pointer delegate. my code is as follows: void Graph::addNodes (NodeSet& nodes) { for (NodeSet::iterator pos = nodes.begin(); pos != nodes.end(); ++pos) { addNode(*pos); } } Here NodeSet is defined as: typedef std::set NodeSet; The above piece of code works perfectly on my windows machine, but when i run the same piece of code on a MAC, it gives me the following error: no matching function for call to 'Graph::addNode(const boost::shared_ptr&)' FYI, Node_ptr is of type: typedef boost::shared_ptr Node_ptr; can somebody plz tell me why this is happening?

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• Escaping and unescaping a string with single and double quotes in Javascript

  - by Reina

  I have a search box that a user can search for any string including single AND double quotes, once they have searched, the backend is passing the keyword back to me so I can put it back in the box. I don't know what the string is so I can't escape quotes myself, below is an example: var keyword = "hello"; $("#selectionkeywords").val(); The issue I am having is that if the user enters "hello" the keyword becomes ""hello"" and I get this error: missing ) after argument list [Break On This Error] jQuery("#selectionkeywords").val(""hello""); The user could also enter single quotes so that rules it out as well. I tried using escape unescape but I still have the same issue e.g. escape(""hello"") I could get the value in an unescaped format e.g. "hello" but I don't know what to do with it, escape doesn't work on it I end up with this %26%23034%3Bhello%26%23034%3B So I'm pretty much stuck at the moment as I can't do anything to the string, any ideas?

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• C Structure Pointer Problem

  - by Halo

  I have this struct; #define BUFSIZE 10 struct shared_data { pthread_mutex_t th_mutex_queue; int count; int data_buffer_allocation[BUFSIZE]; int data_buffers[BUFSIZE][100]; }; and I want to allocate one of the data_buffers for a process, for that purpose I execute the following function; int allocate_data_buffer(int pid) { int i; for (i = 0; i < BUFSIZE; i++) { if (sdata_ptr->data_buffer_allocation[i] == NULL) { sdata_ptr->data_buffer_allocation[i] = pid; return i; } } return -1; } but the compiler warns me that I'm comparing pointer to a value. When I put a & in front of sdata_ptr it calms down but I'm not sure if it will work. Isn't what I wrote above supposed to be true?

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• how do you find the exact variable of a null pointer exception

  - by OVERTONE

  I've been at this one for a bit now. I've got a null pointer exception so im guessing somethings not been initialized. AdminMessages.inbox1.setText(messageRsetArray[0]); thats my code where its targetting. but i cant find what inside it hasnt been initiazed. AdminMessages is a class which contains a JTextField called inbox1, messageRsetArray is an array which has taken variables from an array. also inbox1 is static. i coulndt get the getters and setter to work. i know its bad practice though.

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• custom ListView --Null pointer exception

  - by raghs

  this code throws a Null pointer exception. It was thrown by getChildAt(i). The getCount() returns the number of items in listView. But getChildAt(i) returns only if item is present in current list view. For example in a scrollable list view assume that there are 20 items. The getCount() returns 20. But getChildAt(20) returns null. Because it doesnot fit in listview. How to solve this problem?? int i,j=object.getCount(); View v=getListView(); CheckBox chk=null; for(i=0;i<j;i++) { chk=((CheckBox)((ViewGroup) v).getChildAt(i).findViewById(R.id.checkBox1)); if(chk.isChecked()) { //download the contents to specific folder in sd card } }

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• Propor usage of double and single quotes?

  - by Phox

  I'm talking about the performance increase here. From all I know you can echo variables in double quotes ("), like so: <?php echo "You are $yourAge years old"; ?> But single quotes will just return You are $yourAge years old. But what about performance differences? I've always gone by the rule that single quotes are faster because the PHP interpreter doesn't have to search through the string for variables. But I'm seeing more and more blog and forum posts on the web saying differently. Does anyone actually have any information on this subject? Perhaps benchmark tests or something? Cheers.

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• NULL pointer dereference in C

  - by user554125

  hey ive got this piece of code. It dereferences a null pointer here. But then there is an and with unsigned int. I really dont understand the whole part. Can someone explain the output.?? struct hi { long a; int b; long c; }; int main() { struct hi ob={3,4,5}; struct hi *ptr=&ob; int num= (unsigned int) & (((struct hi *)0)->b); printf("%d",num); printf("%d",*(int *)((char *)ptr + (unsigned int) & (((struct hi *)0)->b))); } The o/p i get is 44 .But how does it work?

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• Syncronizing indices of function pointer table to table contents

  - by Thomas Matthews

  In the embedded system I'm working on, we are using a table of function pointers to support proprietary Dynamic Libraries. We have a header file that uses named constants (#define) for the function pointer indices. These values are used in calculating the location in the table of the function's address. Example: *(export_table.c)* // Assume each function in the table has an associated declaration typedef void (*Function_Ptr)(void); Function_Ptr Export_Function_Table[] = { 0, Print, Read, Write, Process, }; Here is the header file: *export_table.h* #define ID_PRINT_FUNCTION 1 #define ID_READ_FUNCTION 2 #define ID_WRITE_FUNCTION 3 #define ID_PROCESS_FUNCTION 4 I'm looking for a scheme to define the named constants in terms of their location in the array so that when the order of the functions changes, the constants will also change. (Also, I would like the compiler or preprocessor to calculate the indices to avoid human mistakes like typeo's.)

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