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  • C++: Cannot convert from foo& to foo*

    - by Rosarch
    I have a method: odp(foo& bar); I'm trying to call it: foo baz; odp(&baz); I get a compiler error: error C2664: "odp" cannot convert parameter 1 from 'foo *' to 'foo &' What am I doing wrong? Aren't I passing in a reference to baz? UPDATE: Perhaps I have a misconception about the relationship between pointers and references. I thought that they were the same, except references couldn't be null. Is that incorrect?

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  • C++: ptr->hello(); /* VERSUS */ (*ptr).hello();

    - by Joey
    i was learning about c++ pointers... so the "-" operator seemed strange to me... instead of ptr-hello(); one could write (*ptr).hello(); because it also seems to work, so i thought the former is just a more convenient way is that the case or is there any difference?

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  • Basic help needed with pointers

    - by sbsp
    Hi, i asked some time ago on an account i cant remember how to manipulate basic pointers and someone gave me a really good demo for example char *ptr = hello (hello = a char array) so now *ptr is pointing at h ptr++ = moves the ptr to point at the next element, to get its value i do *ptr and that gives me e ok so far i hope :D but now i need to manipulate a char **ptr and was wondering how i do this in a way that mimmicks the effects of a 2d array? some basic tips would be much appreciated as i need to do an assignment that has a **ptr to immitate a 2d array and without knowing how it does this first means i cant even solve it on paper (for example, how do you dereference a **ptr, how do you get [x][y] values etc) thanks

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  • Building 16 bit os - character array not working

    - by brainbarshan
    Hi. I am building a 16 bit operating system. But character array does not seem to work. Here is my example kernel code: asm(".code16gcc\n"); void putchar(char); int main() { char *str = "hello"; putchar('A'); if(str[0]== 'h') putchar('h'); return 0; } void putchar(char val) { asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"m"(val) ) ; } It prints: A that means putchar function is working properly but if(str[0]== 'h') putchar('h'); is not working. I am compiling it by: gcc -fno-toplevel-reorder -nostdinc -fno-builtin -I./include -c -o ./bin/kernel.o ./source/kernel.c ld -Ttext=0x9000 -o ./bin/kernel.bin ./bin/kernel.o -e 0x0 What should I do?

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  • Multiple left joins, how to output in php

    - by Dan
    I have 3 tables I need to join. The contracts table is the main table, the 'jobs' and 'companies' table are extra info that can be associated to the contracts table. so, since I want all entries from my 'contracts' table, and the 'jobs' and 'companies' data only if it exists, I wrote the query like this.... $sql = "SELECT * FROM contracts LEFT JOIN jobs ON contracts.job_id = jobs.id LEFT JOIN companies ON contracts.company_id = companies.id ORDER BY contracts.end_date"; Now how would I output this in PHP? I tried this but kept getting an undefined error "Notice: Undefined index: contracts.id"... $sql_result = mysql_query($sql,$connection) or die ("Fail."); if(mysql_num_rows($sql_result) > 0){ while($row = mysql_fetch_array($sql_result)) { $contract_id = stripslashes($row['contracts.id']); $job_number = stripslashes($row['jobs.job_number']); $company_name = stripslashes($row['companies.name']); ?> <tr id="<?=$contract_id?>"> <td><?=$job_number?></td> <td><?=$company_name?></td> </tr> <? } }else{ echo "No records found"; } Any help is appreciated.

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  • How to check if the internal typedef struct of a typedef struct is NULL ?

    - by watchloop
    typedef struct { uint32 item1; uint32 item2; uint32 item3; uint32 item4; <some_other_typedef struct> *table; } Inner_t; typedef struct { Inner_t tableA; Inner_t tableB; } Outer_t; Outer_t outer_instance = { {NULL}, { 0, 1, 2, 3, table_defined_somewhere_else, } }; My question is how to check if tableA is NULL just like the case for outer_instance. It tried: if ( tmp->tableA == NULL ). I get "error: invalid operands to binary =="

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  • Cant free memory.

    - by atch
    In code: int a[3][4] = {1,2,3,4, 5,6,7,8, 9,10,11,12}; template<class T, int row, int col> void invert(T a[row][col]) { T* columns = new T[col]; T* const free_me = columns; for (int i = 0; i < col; ++i) { for (int j = 0; j < row; ++j) { *columns = a[j][i]; ++columns;//SOMETIMES VALUE IS 0 } } delete[] free_me;//I'M GETTING ERROR OF HEAP ABUSE IN THIS LINE } int main(int argc, char* argv[]) { invert<int,3,4>(a); } I've observed that while iterating, value of variable columns equals zero and I think thats the problem. Thanks for your help.

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  • Using C++ is a Linked-List implementation without using pointers possible or not?

    - by sonicoder
    My question is very simply, can one using C++, implment a link-list data structure without using pointers (next nodes)? To further qualify my question, I'm mean can one create a Linked-List data structure using only class instantiations. A common node definition might be like so: template<typename T> struct node { T t; node<T>* next; node<T>* prev; }; I'm aware of std::list etc, I'm just curious to know if its possible or not - and if so how? code examples will be greatly appreciated.

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  • Vector of objects

    - by Paul
    I've got a abstract class class A { public: virtual void somefunction() = ; }; and some different classes that inherit this class: class Ab { public: void somefunction(); }; etc. I want to make a vector containing some objects of these classes (how many depends on input parameters) so I can access these easily later. However I'm a bit lost on how to do this. My best idea is vector<A> *objectsVector; Ab AbObject; objectsVector.push_back(AbObject); However this gives me a huge amout of errors from various .h files in /usr/include/c++ How should i solve this?

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  • C++ calculation evaluated to 0

    - by Alexander Stolz
    I'm parsing a file and trying to decode coordinates to the right unit. What happens is that this code is evaluated to 0. If I type it into gdb the result is correct. int pLat = (int)( (argv[6].data() == "plus" ? 1 : -1) * ( atoi(argv[7].data()) + atoi(argv[8].data()) / 60. + atoi(argv[9].data()) / 36000.) * 2.145767 * 0.0001); P.s. If someone knows a better title for this question, please change it

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  • C++ Compound Interest Exercise

    - by Lameste
    I'm a beginner trying to learn C++ using "C++ Primer Plus Sixth Edition". I'm on Chapter 5, going over loops. Anyways I was doing this programming exercise from the book, the problem is: Daphne invests $100 at 10% simple interest.That is, every year, the investment earns 10% of the original investment, or $10 each and every year: interest = 0.10 × original balance At the same time, Cleo invests $100 at 5% compound interest.That is, interest is 5% of the current balance, including previous additions of interest: interest = 0.05 × current balance Cleo earns 5% of $100 the first year, giving her $105.The next year she earns 5% of $105, or $5.25, and so on.Write a program that finds how many years it takes for the value of Cleo’s investment to exceed the value of Daphne’s investment and then displays the value of both investments at that time. Here is the code I have written for this exercise, I'm not getting good results though. #include <iostream> #include <array> double Daphne(int, double, double); double Chleo(double, double); int main() { using namespace std; int p = 100; //Principle double i1 = 0.1; // 10% interest rate double i2 = 0.05; // 5% interest rate double dInv = 0; //Daphnes investment double cInv = 0; // Chleos investment int t=1; //Starting at year 1 double s1 = 0; //Sum 1 for Daphne double s2 = 0; // Sum 2 for Chleo s1 = p + 10; //Initial interest (base case after year 1) for Daphne s2 = p + (i2*p); //Initial interest (base case after year 1) for Chleo /*cout << s1 << endl; cout << s2 << endl;*/ while (cInv < dInv) { dInv = Daphne(p, i1, s1); cInv = Chleo(i2, s2); t++; } cout << "The time taken for Chleos investment to exceed Daphnes was: " << t << endl; cout << "Daphnes investment at " << t << " years is: " << dInv << endl; cout << "Chleos invesment at " << t << " years is: " << cInv << endl; system("pause"); return 0; } double Daphne(int p, double i, double s1) { s1 = s1 + (p*i); return s1; } double Chleo(double i, double s2){ s2 = s2 + (s2*i); return s2; } Output from console: The time taken for Chleos investment to exceed Daphnes was: 1 Daphnes investment at 1 years is: 0 Chleos invesment at 1 years is: 0 Press any key to continue . . . Can anyone explain why I'm getting this current result? The while loop is supposed to continue executing statements until Chleo's investment exceeds Daphnes.

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  • Are doubles faster than floats in c#?

    - by Trap
    I'm writing an application which reads large arrays of floats and performs some simple operations with them. I'm using floats because I thought it'd be faster than doubles, but after doing some research I've found that there's some confusion about this topic. Can anyone elaborate on this? Thanks.

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  • Fetching a result twice with deferend name

    - by user1799842
    I have 1 table with tasks named opentask:columns: id,title,description,expires,creator_id,creator_name, executer_id, executer_name, priority_id, status_id1 table with users named user: with columns: user_id, username What I want is to create a query where there will be all columns from opentask table where the executer_id will be equal to the user_id of user table AND the creator_id will be equal to the user_id again. This creates a confusion because the first equality excludes the second.So I need somehow to create a query where I will include the usernames for the executer with something like where "opentask.executer_id=user_user_id" and at the same time I will include the username again (as a differend name?) for the creator with something like "where opentask.executer_id=user_user_id"So I try this, which of course I know that is missing something, can you help? SELECT DISTINCT id, title, description, expires, creator_id, executer_id, oc_opentask.priority_id, oc_opentask.status_id, priority_name, status_name, user_id, username, (SELECT username FROM oc_opentask, oc_user WHERE oc_opentask.creator_id=oc_user.user_id) AS username2 FROM oc_opentask, oc_opentask_priority, oc_user, oc_opentask_status WHERE oc_opentask.priority_id=oc_opentask_priority.priority_id AND oc_opentask.executer_id=oc_user.user_id AND oc_opentask.status_id=oc_opentask_status.status_id ORDER BY oc_opentask.expires DESC

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  • How do game trainers change a address in memory thats dynamic?

    - by GameTrainersWTF
    Lets assume i am a game and i have a global int* that contains my health. A game trainers job is to modify this value to whatever in order to achieve god mode. I've looked up tutorials on game trainers to understand how they work, and the general idea is to use a memory scanner to try and find the address of a certain value. Then modify this address by injecting a dll or whatever. But i made a simple program with a global int* and its address changes every time i run the app, so i don't get how game trainers can hard code these addresses? Or is my example wrong? What am i missing?

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  • How do game trainers change an address in memory that's dynamic?

    - by GameTrainersWTF
    Lets assume I am a game and I have a global int* that contains my health. A game trainer's job is to modify this value to whatever in order to achieve god mode. I've looked up tutorials on game trainers to understand how they work, and the general idea is to use a memory scanner to try and find the address of a certain value. Then modify this address by injecting a dll or whatever. But I made a simple program with a global int* and its address changes every time I run the app, so I don't get how game trainers can hard code these addresses? Or is my example wrong? What am I missing?

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  • C++ sort array of char pointes

    - by user69514
    Can you tell me what's wrong with my method? I ends up putting the same thing everywhre and it's actually not sorting. void sortArrays(){ int i, j; for(i=0; i<counter; i++){ for( j=0; j<i; j++){ if( strcmp(title_arr[i], title_arr[j]) < 0){ char* title_temp = title_arr[i]; title_arr[j] = title_temp; } } }

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  • Heap Error in C++

    - by BobAlmond
    Dear all, I'm a beginner programmer in C++. Recently, I'm working on image processing thing using C++. but I have some problem that I want to ask. Suppose I have some code as follow: for (int i=0;i<100000;i++) { int * a = new int[10000]; //do something delete [] a; } When I executed that code, I receive runtime error, Heap Error... Is there anything wrong with that code, I mean, can I allocate memory and release it in the same loop? Thanks in advance...

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  • C++ sort array of char pointers

    - by user69514
    Can you tell me what's wrong with my method? I ends up putting the same thing everywhre and it's actually not sorting. void sortArrays(){ int i, j; for(i=0; i<counter; i++){ for( j=0; j<i; j++){ if( strcmp(title_arr[i], title_arr[j]) < 0){ char* title_temp = title_arr[i]; title_arr[j] = title_temp; } } }

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  • Getting touchpad to work in desktop ubuntu

    - by kamziro
    I bought a small touchpad to stick on top of the keyboard, and it works fine on the windows computer, but not on my ubuntu desktop. I mean, when I do "xinput list" it shows the following: ? Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? PIXART USB OPTICAL MOUSE id=8 [slave pointer (2)] ? ? Logitech USB-PS/2 Optical Mouse id=11 [slave pointer (2)] ? ? Microsoft Wired Keyboard 600 id=13 [slave pointer (2)] ? ? Macintosh mouse button emulation id=14 [slave pointer (2)] ? ? Cirque Corporation 9925 AG Touchpad id=15 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Power Button id=7 [slave keyboard (3)] ? No brand SP04-A1 id=9 [slave keyboard (3)] ? Elite Silicon USB Audio Device id=10 [slave keyboard (3)] ? Microsoft Wired Keyboard 600 id=12 [slave keyboard (3)] The Cirque Corporation touchpad (I'm assuming that's the component name) is the touchpad. Is there anything I'm missing?

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