I was struggling the last 2 days with this C script supposing to open a list of strings (input as fopen(argv[1])and allowing to access to any element of the list. I created an array *gcm[10000] and a pointer *(*gcm_ptr[10000] = &gcm. However, when I try to list whatever n[i], it always gives me the last entry.
View 4 Repliesi have been fiddling with pointers but I don't understand how the proper syntax is written when I want to acces an element of an array through a pointer to a pointer...The code is all mostly just random bs for learning purposes. I marked the problem "// THIS LINE"
Code:
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#define MAX_DATA 100
int find_average(char *iden, ...) {
[Code]...
This is a sample program that declares a Matrix as a structure with an array as a pointer to a pointer. The following program is supposed to store a matrix in the structure "_Matrix" and later print the matrix just entered but it fails giving me a "segmentation fault". The sample code is given below
Code:
#include <stdio.h>
#include <stdlib.h>
struct _Matrix {
int row_size;
int col_size;
int **mat;
[Code] ......
I have the records "File attached"
My query is
from c in JOB_HISTORies join d in DEPARTMENTs on c.DEPARTMENT_ID equals d.DEPARTMENT_ID select new {d.DEPARTMENT_NAME,c.START_DATE,c.END_DATE}
How do i put the record Accounting in the same row to avoid duplication.
I have a C# program going and want to be able to call the DLL and receive back the data requested through a pointer.Below is the DLL import within my C# code.
Code:
[DllImport("MyTest.dll")]
public static extern int ReadNetwork(Byte[] ROM_ID); Below is the code in the DLL Code: int _stdcall ReadNetwork(unsigned char* Array1)
{
ReadDevice(readBackArray);
for(i = 0; i < 20; i++)
{
Array1[i] = readBackArray[i];
}
[code]....
I've tried changing the return values in the DLL's ReadNetwork() function and that works ok, so I know I'm calling the DLL and it runs ok, but printing the result back is where I'm having the problem.
I am trying to retrieve the first three bits of a number. The code that I am using should work but it isn't giving me the correct result when trying certain numbers. Below is the code I am using:
unsigned short num1, num2 = 0;
unsigned short num = 65535// binary 111111111111111
num1 = num && 0x07;// gives me 1 but should give 7(111)
num2 = num >>3;//gives me 8191, which is correct
Why I am not getting the first three correct bits(111)?
When i execute the program it gets the right data for the first array but the scound either doesn't work at all or just gets to much data. i've tryed using getline and the "cin" for what the file would be in this case "myfile" there is also one more array that must be retrieved from the file.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
[Code].....
I have the following code :
Code:
#ifndef TDYNAMICARRAY_H
#define TDYNAMICARRAY_H
namespace Massive {
template<class T>
T **AllocateDynamic2DArray(int nRows,int nCols)
[Code] .....
I wish to know how to traverse or loop through a dynamic 2D array using pointer to pointer as returned by the code above. Like I would in a static T[20][20] 2D array.
I have a text file config.txt which has:
"red = true"
"blue = false"
"children = 10"
I want to write a code that reads the values of these variables red, blue and children when executing the code.
I have something like this:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main () {
ifstream Configure;
[Code] .....
I want to read the read the values of red, blue and children in and use them when the program executes.
I'm writing a simple text adventure style program in order to practice C++. I originally used char to get whether the user wanted to go north, south etc, requiring they enter W, A, S, or D, and then I used a switch statement, rather than a bunch of else if blocks to move in the appropriate direction. Last night I started updating the code and wanted to require the user type an actual string like "go north" to move, so I'm in the process of converting it over to getline();.
The way it works is the user will input "go north", and if the string is equal to "go north" it will set a variable to 1, 2, 3, or 4, so I can keep the switch statement. The program compiles but whenever it asks for user input, it always hangs waiting for 2 separate lines of input regardless of whether or not you put a space between your command. The move function is as follows:
void movement() {
bool loop = true;
int roomNorth = 0;
int roomWest = 0;
int roomSouth = 0;
int roomEast = 0;
int dirOption;
string dir = "";
[code]....
I read that it could be an issue with getline and the new line characters, which is why I added the cin.ignore in there...so yea the code will wait for 2 separate lines of input and then always outputs "Invalid direction!" regardless of the input.
I have a vc++ project file which reads data from access 2007 database.
I have successfully declared and opened connectionPtr and recordSetPtr objects.
The follwoing code is giving an error message that "item cannot be found in the collection"
stringVar = (recordSet->Fields->GetItem("[String]")->GetValue()).bstrVal;
If i replace "[String]" with "String" then above statement executed successfully.
How can i execute the above statement with "[String]" without errors?
I have issues for the following piece of code :
Code:
#include <string>
#include <fstream>
#include <iostream>
#include <cstdlib>
[Code] ....
I get errors retrieving the grade values extracted, and then I get a run time fault.
I want to get or view the SIM card number from the dongle (the dongle will b already connected to the computer where the SIM card will be inserted into it) but the coding should be done by C programming / Language.
View 5 Replies View RelatedI am supposed to make this phone book save to a file and then be able to retrieve it.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Phonebook_Contacts
{
char FirstName[20];
char LastName[20];
char PhoneNumber[20];
} phone;
}
[code]....
Suppose your program has many concrete subtypes of Person, and each person will have their own file saved, with their type stored in that file. When reading the files to create the people again (of their proper types), what is the best method to maximize performance (and elegance by shortening the code)? Here is what I have so far.
First I used if statements, which is terrible, and now I've improved the performance logarithmically using std::map. I still suspect there is a better way, especially if there are going to be hundreds of different classes. If you want to test it, you can change the PATH constant to whatever path you want, or just leave it as an empty string, and the files will be created in the same directory as your cpp file. The part I'm trying to improve is pointed out in the comments.
struct Person {
std::string name;
Person (const std::string& newName) : name (newName) {}
virtual ~Person() = default;
};
struct Guy : Person {using Person::Person;};
struct Girl : Person {using Person::Person;};
[Code] ....
I have to store large amount of data and retrieve the same data then write into file in C++. Currently I am using vector to store and retrieve. But vector is taking more time to store and retrieve the element. Is any other best data structure to store and retrieve large amount of data in unordered way?
Example code:
int I1 = 700,I2 = 32, I3 = 16;
//declare and resize the vector size
vector< vector < vector < vector<DOUBLE> > > > vPARAM;
vPARAM.resize(I1, vector< vector < vector<DOUBLE> > >
[Code] ....
My specific request is for retrieving values that are stored to a CompactFlash card. I am able to store values (we call them recipes) to the CompactFlash card as .csv file. I just haven't been able to figure out the code to retrieve this information back to the touchscreen.
Code:
// Create a new folder if it doesn't exist
CreateDirectory("/recipes");
//Create the file if it doesn't exist
CreateFile("/recipes/recipe.csv");
//open the file
hfile = OpenFile("/recipes/recipe.csv", 2);
[Code]....
Now with that said, I would like to retrieve these values from the .csv file.
I am trying to retrieve the parameters from externally connected pendrive. I have been using WMI to achieve this but not able to separate the pendrive's parameters from the other USB devices (such as USBcamera,USBHub etc) ....
View 2 Replies View RelatedWhat is the efficiency of the two assignments (line 1 and 2), i.e. (function calls, number of copies made, etc), also the Big O notation. I know there are function calls for retrieving the size of each string in order to produce a new buffer for the concatenated string...any difference between line 1 and 2 in terms of efficiency?
String s("Hello");
String t("There");
1. s = s + t;
2. s += t;
I would like to have 2 functions. (FYI, I haven't even tested these because I don't have a compiler on this PC, so don't know what they'll do. I'm also new to C++, self-teaching.)
My question is, I'm sure that oFile should be type object (of some sort), not int, but I'm not sure how to reference it correctly so that it passes from FileOpen to main to FileClose.
Code:
#include <iostream> //I/O
using namespace std;
#include <fstream> //files
using namespace ios;
int FileOpen(string fileName) {
ifstream oFile (fileName); //attempt to open file
[Code] ....
In my refference book I have got a example with a part saying to access the a[4][0] element of the array (named a) with pointer this can be written:
*((int*)a+4)
I wonder if the cast is really required. The book says it is required so that the pointer arithmetic can be done properly. However I am not sure about it. When I work with pointers defined by myself I don't use casts similar to this one. Is there a difference between a self defined pointer and array name?
I have written this code, and at first glance it does what I want, however I am worried that
a) I am overwriting the array that is apssed from chord.getPattern()
b) Im getting a memory leak that I want to get rid of, and
c) is there generally a /what is the neater way to do it:
Code:
uint8_t* ChordBuilder::invert(uint8_t count, Chord chord) {
temp = chord.getPattern();
chord.invert(true);
//TODO count is how many times to invert. Moves root aswell however
for (uint8_t i = 0; i < count; i++){
[Code] ....
temp is a member variable of ChordBuilder - and is expressed as: Code: uint8_t* temp; I dont want the pattern that chord stores, and passes with getPattern() to change - I fear it is at the moment?
I would rather not use the "new" but I cant think how to get rid of it, however Im not sure where I would need to put the "delete"?
What is the correct method of declaring pointer to multidimensional array
Code:
int array[3][4];
int *p = array;
The above code works but it shows warning. Is it an invalid way of using the pointer? the array is an address then why am i getting warning?
I have the following situation:
Code:
void myFun(float *pfMyPtr) {
float Val[] = {0.234, 0,432, 0.322, 0762, 0.984};
pfMyPtr = Val;
}
int main() {
float *pfPtr;
pfPtr = (float*) calloc (5,sizeof(float));
myFun(pfPtr);
}
I would like pfPtr to contain the values of array Val. What am I missing here?
int * ptr = new int[5];
p += 2; //p now stores address of 3rd element in array
delete [] p;
what will be deleted??? all 5 elements or just 3rd, 4th and 5th elements of array(in result making a memory leak)
Why would you ever assign a pointer to an existing array?Take this link for example. URL....I understand that pointers use dynamic memory allocation so they are much more flexible then a built in array, but if you already have an existing array, don't you already have static memory allocation for that array? Why bother assigning a pointer? Regardless of the pointer, doesn't the program still allocate static memory to the array anyway?
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