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• What is XcvPort (used in OpenPrinter function)

  - by RiskX

  I'm usin the OpenPrinter function and the first parameter the function gets called "pPrinterName" and that's it's MSDN description: [in] Pointer to a null-terminated string that specifies the name of the printer or print server, the printer object, the XcvMonitor, or the XcvPort. For a printer object use: PrinterName,Job xxxx. For an XcvMonitor, use: ServerName,XcvMonitor MonitorName. For an XcvPort, use: ServerName,XcvPort PortName. Obviously I'm interested in the bold part. What exactly is XcvPort? I know it seems like a question of lazy person but I really couldn't find info abou this concept. If I would like to open a printer on port ABC I should write: "\\MySrever,XcvPort ABC"? Thank you for your answers!

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• usage of 2 charectors in single qoutes in c

  - by user1632141

  #include<stdio.h> int main() { char ch = 'A'; printf("%d\n",'ag'); printf("%d\n",'a'); printf("%d, %d, %d, %d", sizeof(ch), sizeof('a'), sizeof('Ag'), sizeof(3.14f)); return 0; } I used to have many doubts on the output of this question while running on g++ and gcc. But I have cleared almost all the doubts by referring these links: Single and double quotes in C/C++ Single quotes vs. double quotes in C I still need to understand one thing about the output of this question. Can someone please explain the output of printf("%d\n",'ag'); mentioned above in the program. How is it actually stored in the memory? The output for the program on the Linux/GCC platform is: 24935 97 1, 4, 4, 4

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• C++ conditional compilation

  - by Shaown

  I have the following code snippet #ifdef DO_LOG #define log(p) record(p) #else #define log(p) #endif void record(char *data){ ..... ..... } Now if I call log("hello world") in my code and DO_LOG isn't defined, will the line be compiled, in other words will it eat up the memory for the string "hello world"? P.S. There are a lot of record calls in the program and it is memory sensitive, so is there any other way to conditionally compile so that it only depends on the #define DO_LOG? Thanks in advance.

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• <function> referenced from; symbol(s) not found.

  - by jfm429

  I have a piece of C code that is used from a C++ function. At the top of my C++ file I have the line: #include "prediction.h" In prediction.h I have this: #ifndef prediction #define prediction #include "structs.h" typedef struct { double estimation; double variance; } response; response runPrediction(int obs, location* positions, double* observations, int targets, location* targetPositions); #endif I also have prediction.c, which has: #include "prediction.h" response runPrediction(int obs, location* positions, double* observations, int targets, location* targetPositions) { // code here } Now, in my C++ file (which as I said includes prediction.h) I call that function, then compile (through Xcode) I get this error: "runPrediction(int, location*, double*, int, location*)", referenced from: mainFrame::respondTo(char*, int)in mainFrame.o ld: symbol(s) not found collect2: ld returned 1 exit status prediction.c is marked for compilation for the current target. I don't have any problems with other .cpp files not being compiled. Any thoughts here?

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• trying to make an accordion menu from a list - jquery indexhibit

  - by orionrush

  Hello - Im teaching my self javascript & jquery so this might be a bit of a low brow question or entirely too much code for anyone to wade through, but Im hoping for some feedback. I have looked around and haven't found a thread that looks like it will deals neatly with my question. Im using the cms indexhibit (cant create a new tag!) and trying to create an accordion style menu from the menu list it generates. I basically have the behaviour Im after, modifying an existing bit of work but there are quite a few foibles, which are no doubt a conflict between the .click and .toggle and a confused use if statements. I basically want to start from scratch and redo this so I can a) learn from my mistakes b) understand what's happening. Im having trouble now because I dont know where to go from here, or how to trouble shoot it. Can anyone give me a quick analysis how the the script in the head of the document work together? Also any insight into the nature of the conflicts Im seeing and what approach might take to remedy them? If you were going to start afresh what would be your approach? Here is a test to see it in action (warts and all): http://stillstatic.nfshost.com/ This script goes into the document head: <script type='text/javascript'> //im not entirely clear as to what this achieves path = 'path/to/script/'; $(document).ready(function() { setTimeout('move_up()', 1); expandingMenu(0); expandingMenu(1); expandingMenu(2); expandingMenu(3); expandingMenu(4); //etc }); </script> the generated list: <ul> <li class='section-title active_menu'>blogs</li> <li><a class="active" href='#' onclick="do_click();">3</a></li> </ul> <ul> //this menu section dose not have a label: class .section-title <li><a href='#' onclick="do_click();">1</a></li> <li><a href='#' onclick="do_click();">2</a></li> </ul> <ul> //this menu section is not the 'active menu' this is achieved by the jquery script <li class='section-title'>writing</li> <li><a href='#' onclick="do_click();">4</a></li> <li><a href='#' onclick="do_click();">5</a></li> </ul> The meat of in an external script: function expandingMenu(num) { var speed = 500; var menu_title = $("#menu ul").eq(num).children(":first"); // ie. first child be the title with the class .section-title unless the user turned it off var menu_items = $("#menu ul").eq(num).children().filter(function (index) { return index 0; }); // ie. any li NOT in position 0, below li.section-title if (menu_items.is(".active") == true) { menu_title.addClass("active_menu"); //Add a class to the active list so we can style it. } if (menu_title.is(".section-title") == true){ // this if prevents interference with users who turn off the section titling if ((menu_items.is(".active") == false) && (menu_items.is(":visible")) ) { menu_items.hide(0);// first we hide the inactive exhibits } $('li').click(function (){ if ( (menu_title.is(":visible") == true) ){ menu_items.hide(speed); } if ( (menu_items.is(":hidden") == true ) && (('')) ){// ?! without this second condition things break down. . . menu_items.show(speed); } }) menu_title.css({cursor:"pointer"}).toggle( // add click functions + pointer to menu_title function () { menu_items.show(speed);//Open it up }, function () { // this function could even be empty but without the if things get weird if (menu_items.is(".xx")) menu_items.hide(speed); //Take the menu item off of active duty! } ) } }

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• Reducing template bloat with inheritance

  - by benoitj

  Does anyone have experience reducing template code bloat using inheritance? i hesitate rewriting our containers this way: class vectorBase { public: int size(); void clear(); int m_size; void *m_rawData; //.... }; template< typename T > class vector : public vectorBase { void push_back( const T& ); //... }; I should keep maximum performance while reducing compile time I'm also wondering why stl implementations do not uses this approach Thanks for your feedbacks

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• typedef declaration syntax

  - by mt_serg

  Some days ago I looked at boost sources and found interesting typedef. There is a code from "boost\detail\none_t.hpp": namespace boost { namespace detail { struct none_helper{}; typedef int none_helper::*none_t ; } // namespace detail } // namespace boost I didn't see syntax like that earlier and can't explain the sense of that. This typedef introduces name "none_t" as pointer to int in boost::detail namespace. What the syntax is? And what difference between "typedef int none_helper::*none_t" and for example "typedef int *none_t" ?

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• How to build up a lookup table in microcontroller?

  - by GiGi

  Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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• Interrupting `while loop` with keyboard in Cython

  - by linello

  I want to be able to interrupt a long function with cython, using the usual CTRL+C interrupt command. My C++ long function is repeatedly called inside a while loop from Cython code, but I want to be able, during the loop, to send an "interrupt" and block the while loop. The interrupt also should wait the longFunction() to finish, so that no data are lost or kept in unknown status. This is one of my first implementation, which obviously doesn't work: computed=0; print "Computing long function..." while ( computed==0 ): try: computed = self.thisptr.aLongFunction() except (KeyboardInterrupt, SystemExit): computed=1 print '\n! Received keyboard interrupt.\n' break; (p.s. self.thisptr is the pointer to the current class which implements aLongFunction() )

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• jQuery click event not working when mouse moves from one div to another with button held down

  - by Acorn

  I've made a page that uses jQuery to allow you to place <div>s on the page based on your mouse coordinates when you click. The page And here's the javascript: $('document').ready(function() { $("#canvas").click(function(e){ var x = e.pageX - this.offsetLeft; var y = e.pageY - this.offsetTop; $(document.createElement('div')).css({'left':x + 'px', 'top':y + 'px'}).addClass('tile').appendTo('#canvas'); }); }); I've found that if you mousedown in the div#canvas and mouseup with your pointer over a placed <div> (or vice versa) then a new <div> doesn't get placed. Why is this?

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• So, I guess I can't use "&&" in the Python if conditional. Any help?

  - by Sergio Tapia

  Here's my code: # F. front_back # Consider dividing a string into two halves. # If the length is even, the front and back halves are the same length. # If the length is odd, we'll say that the extra char goes in the front half. # e.g. 'abcde', the front half is 'abc', the back half 'de'. # Given 2 strings, a and b, return a string of the form # a-front + b-front + a-back + b-back def front_back(a, b): # +++your code here+++ if len(a) % 2 == 0 && len(b) % 2 == 0: return a[:(len(a)/2)] + b[:(len(b)/2)] + a[(len(a)/2):] + b[(len(b)/2):] else: #todo! Not yet done. :P return I'm getting an error in the IF conditional. What am I doing wrong?

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• C optimization breaks algorithm

  - by Halpo

  I am programming an algorithm that contains 4 nested for loops. The problem is at at each level a pointer is updated. The innermost loop only uses 1 of the pointers. The algorithm does a complicated count. When I include a debugging statement that logs the combination of the indexes and the results of the count I get the correct answer. When the debugging statement is omitted, the count is incorrect. The program is compiled with the -O3 option on gcc. Why would this happen?

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• Trouble assigning a tr1::shared_ptr

  - by Max

  I've got a class that has a tr1::shared_ptr as a member, like so: class Foo { std::tr1::shared_ptr<TCODBsp> bsp; void Bar(); } In member function Bar, I try to assign it like this: bsp = newTCODBsp(x,y,w,h); g++ then gives me this error no match for ‘operator=’ in ‘((yarl::mapGen::MapGenerator*)this)->yarl::mapGen::MapGenerator::bsp = (operator new(40u), (<statement>, ((TCODBsp*)<anonymous>)))’ /usr/include/c++/4.4/tr1/shared_ptr.h:834: note: candidates are: std::tr1::shared_ptr<TCODBsp>& std::tr1::shared_ptr<TCODBsp>::operator=(const std::tr1::shared_ptr<TCODBsp>&) in my code, Foo is actually yarl::mapGen::MapGenerator. What am I doing wrong?

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• Why is this c++ string concatenation missing a space?

  - by danutenshu

  I am working with c++ strings, and am a beginner at programming. I am expecting: 99 Red Balloons But I am receiving: 99 RedBalloons Why is that? #include <string> #include <iostream> using namespace std; int main() { string text = "9"; string term( "9 "); string info = "Toys"; string color; char hue[4] = {'R','e','d','\0'}; color = hue; info = "Balloons"; text += (term + color + info); cout << endl << text << endl; return 0; }

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• What system does before launching iPhone app's main() function?

  - by Eonil

  My app takes too much time to loading. So I put a NSLog in main() function like this to measure loading time from first: int main(int argc, char *argv[]) { NSLog(@"main"); NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, nil); [pool release]; return retVal; } But, the log displayed at really later time. Default.png displayed about 5 seconds, all loading process completed in 1~2 seconds after log appeared. What's happening before executing main() function on iPhone app?

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• File in binary form

  - by Abhi

  Dear All I want to write data into the file in binary form. I was trying using the mentioned below FILE *fp = fopen("binaryoutput.rgb888", "ab+"); for(int m=0; m<height; m++) { for (int n=0; n< width; n++) { temp = (pOutputImg+m*3+n*3); // here temp is a pointer to a unsigned char fprintf(fp,"%u",*temp); } } fclose(fp); I am able to get data which is strored at pOutputImg but not in binary form. Can anyone guide me the correct step.. Thanks in advance

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• parsing/matching string occurrence in C

  - by David

  I have the following string: const char *str = "\"This is just some random text\" 130 28194 \"Some other string\" \"String 3\"" I would like to get the the integer 28194 of course the integer varies, so I can't do strstr("20194"). So I was wondering what would be a good way to get that part of the string? I was thinking to use #include <regex.h> which I already have a procedure to match regexp's but not sure how the regexp in C will look like using the POSIX style notation. [:alpha:]+[:digit:] and if performance will be an issue. Or will it be better using strchr,strstr? Any ideas will be appreciate it

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• how to parse from command line arguements in yacc ?

  - by user205688

  how to parse from command line arguements in yacc ? of course i undefined input in both lex & yacc and then wrote int input(void) { printf("in input\n:"); char c; if(target > limit) return 0; if((c = target[0][offset++]) != '\0') return (c); target++; offset =0; return (' '); } where target contains the command line arguements. But only the standard input is getting excueted how to make dis input function get executed.

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• Are raw C++ pointers first class objects?

  - by Shailesh Kumar

  According to Wikipedia: An object is first-class when it: can be stored in variables and data structures can be passed as a parameter to a subroutine can be returned as the result of a subroutine can be constructed at runtime has intrinsic identity (independent of any given name) Somebody had once told me that raw pointers are not first class objects while smart pointers like std::auto_ptr are. But to me, a raw pointer (to an object or to a function) in C++ does seem to me to satisfy the conditions stated above to qualify as a first class object. Am I missing something?

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• Why doesn't Perl threading work when I call readdir beforehand?

  - by Kevin

  Whenever I call readdir before I create a thread, I get an error that looks like this: perl(2820,0x7fff70c33ca0) malloc: * error for object 0x10082e600: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Abort trap What's strange is that it happens when I call readdir before I create a thread (i.e. readdir is not called in any concurrent code). I don't even use the results from readdir, just making the call to it seems to screw things up. When I get rid of it, things seem to work fine. Some example code is below: opendir(DIR, $someDir); my @allFiles = readdir(DIR); close(DIR); my $thread = threads-create(\&sub1); $thread-join(); sub sub1 { print "in thread\n" }

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• Operator + for matrices in C++

  - by cibercitizen1

  I suppose the naive implementation of a + operator for matrices (2D for instance) in C++ would be: class Matrix { Matrix operator+ (Matrix other) const { Matrix result; // fill result with *this.data plus other.data return result; } } so we could use it like Matrix a; Matrix b; Matrix c; c = a + b; Right? But if matrices are big this is not efficient as we are doing one not-necessary copy (return result). Therefore, If we wan't to be efficient we have to forget the clean call: c = a + b; Right? What would you suggest / prefer ? Thanks.

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• SSL_CTX_set_cert_verify_callback vs. SSL_CTX_set_verify

  - by BreakPoint

  Hello, Can anyone tell me what is the difference between SSL_CTX_set_cert_verify_callback and SSL_CTX_set_verify? From OpenSSL docs: SSL_CTX_set_cert_verify_callback() sets the verification callback function for ctx. SSL objects that are created from ctx inherit the setting valid at the time when SSL_new(3) is called. and: SSL_CTX_set_verify() sets the verification flags for ctx to be mode and specifies the verify_callback function to be used. If no callback function shall be specified, the NULL pointer can be used for verify_callback. So I'm trying to understand which callback to send for each one (from client side). Thanks experts.

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• OpenGL texture not showing up on some computers, problem with auxDIBImageLoad?

  - by CptanPanic

  I have a simple openGL GUI that has uses a bmp as a texture. The problem is on some computers the texture doesn't show up. But on ones with newer OpenGL drivers it works. How can I make it more compatible. I think the problem may be with auxDIBImageLoad. When I inspect the result, I see the x,y correct, but the data pointer points to memory bank with all zeros. What could be wrong?

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• Unit testing with serialization mock objects in C++

  - by lhumongous

  Greetings, I'm fairly new to TDD and ran across a unit test that I'm not entirely sure how to address. Basically, I'm testing a couple of legacy class methods which read/write a binary stream to a file. The class functions take a serializable object as a parameter, which handles the actual reading/writing to the file. For testing this, I was thinking that I would need a serialization mock object that I would pass to this function. My initial thought was to have the mock object hold onto a (char*) which would dynamically allocate memory and memcpy the data. However, it seems like the mock object might be doing too much work, and might be beyond the scope of this particular test. Is my initial approach correct, or can anyone think of another way of correctly testing this? Thanks!

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• Column.DbType affecting runtime behavior

  - by leppie

  Hi According to the MSDN docs, the DbType property/attribute of a Column type/element is only used for database creation. Yet, today, when trying to submit data to an IMAGE column on a SQLCE database (not sure if only on CE), I got an exception of 'Data truncated to 8000 bytes'. This was due to the DbType still being defined as VARBINARY(MAX) which SQLCE does not support. Changing the type to IMAGE in the DbType fixes the issue. So what other surprises does Linq2SQL attributes hold in store? Is this a bug or intended? Should I report it to MS? UPDATE After getting the answer from Guffa, I tested it, but it seems for NVARCHAR(10) adding a 11 char length string causes a SQL exception, and not Linq2SQL one. The data was truncated while converting from one data type to another. [ Name of function(if known) = ] A first chance exception of type 'System.Data.SqlServerCe.SqlCeException' occurred in System.Data.SqlServerCe.dll

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