I am having troubles with dynamic arrays and pointers. All the errors are of that kind. I think when I am assigning malloc to an array we assign to its address.
Code:
/*Create an array of genes of the large matrix*/
gene_t gene,gene1,gene2;
gene=malloc(INITIAL*sizeof(gene2)); Code:
while(...) {
if (gene_num==current_size){
[Code] .....
I'm trying to write a function that takes a 32bit address and a data to store at this address.
I'm wanting to take the 32 bit memory address eg 0x12345678 and split it
into 4 x 2 bytes
12, 34, 56, 78
then each of the 4 entries is at most a 256 entry array.eg
FF, FF, FF, FF
So in this example, 0x12 points to 0x34 in the second array, which points to 0x56 in the third array, which finally points to 0x78 in the last array. This last array holds the actual data.
After successfully doing 0x12345678, say I might get a read for 0x1234AABB. So, the first and second pointers already exist, but I then have to create and write to dynamically created arrays.
The arrays need to have all entries set to NULL so that i know whether to follow the pointers to overwrite a previously entered value or create new arrays and pointers.
It all looks good and simple in the pseudo code I've written up but I'm having trouble coding it. I'm currently trying to deal with the first entry case, ie all array elements are NULL, but I'm getting confused with the pointers and creation of new arrays.
void cpu::store(unsigned int mem_add,unsigned int mem_val) {
int first = (mem_address&4278190080)>>24;
int second = (mem_address&16711680)>>16;
int third = (mem_address&65280)>>8;
int fourth= (mem_address&255);
[Code] .....
A1 has been declared as
int* A1[256] ;
Class with Pointers and Dynamic Arrays
View 2 Replies View RelatedI need to use dynamic memory allocation and use pointers to iterate through the arrays that I have already in this program. I am lost, nothing I do works and where to use the pointers. I am just looking for a push in the right direction so I can finish this project and how I can implement pointers in my program.
#include <iostream>
#include <string>
#include <cstdlib>
#include <iomanip>
#include <stdio.h>
using namespace std;
[Code]...
I'm writing a program in which I have to use a matrix to represent a file in code. because it's a file, the size of the matrix is undefined, and therefore the matrix has to be dynamic. I found out that my compiler doesn't like dynamic multidimensional arrays, so I was thinking of this matrix as a dynamic (monodimensional) array of other dynamic (monodimensional) arrays. My program (and thus this example) uses unsigned chars.
unsigned char variable=something;
unsigned char**matrix=new unsigned char*[lenghtOfMainArray];
for(int rowNumber=0;rowNumber<lenghtOfArray;rowNumber++)
{
[Code].....
I have a little problem with one of my functions. The function purpose is to get a number (n) and create an array (size n) with pointers to strings (each string length is 20 chars) and i don't know why but during the debugging i get a <bad ptr> message and this message :
CXX0030: Error: expression cannot be evaluated
This is my function:
Code:
char** getlist(int n) {
int i=0;
char **arr;
arr=(char**)malloc(sizeof(char)*n);
if (arr==NULL)
[Code] ....
The snippet below (or similar) compiles and runs OK but I am using Visual Studio C++ compiler. Are the lines where .nameFirst and .nameLast assigned kosher in ANSI C?
Also I am concerned about the memory allocation for these string constants. Does the runtime system put them on the heap? It doesn't seem that they are really constants since they are not defined before runtime.
Code:
#include "stdlib.h"
typedef struct
{
unsigned id;
char* nameFirst;
char* nameLast;
} myList;
[Code]...
I am attempting to declare an array of pointers dynamically based on user input. I am not sure if A) I'm implementing the syntax of declaring a dynamic array correcntly and B) if my code is set up correctly to print otherwise.
int array_size;
cout << "Please enter the size of the array: " << endl;
cin >> array_size;
if(array_size >= 8) {
cout << "Invalid array size, please enter a valid integer size";
cin >> array_size;
[Code] .....
I know that the synatx for a dynamic array of values is, for example:
int* a = new int[size];
And i understand that "a" is a pointer to the 1st element of the array on the heap.
Now, the syntax for a dynamic array of pointers is:
int** b = new int*[size];
we are currently covering double pointers and memory allocation. Currently getScrabbleWords is not working. when I compile with commented code (Main() works fine) I get a segmentation fault.
This is the purpose of getScrabbleWords:
char **getScrabbleWords(char **allWords, char letters[]):
This function takes an array of char* values (i.e. strings) representing all the words read from wordlist.txt. Each of these words is tested by callingcanWeMakeIt as a helper function, and pointers to the words that can be made are put into an array, myWords. Note, copies of the words are not made! In order to indicate the end of myWords, we terminate with a NULL pointer. Thus, if N words can be made from letters then myWords should have length N+1.
I have the following code here. My questions are:
1. Pointers can be used as pass by reference. When I dynamically allocated memory for array[50] in the run function, does that mean I am changing the size of the pArray in main as well? Or does the scope of array[50] ends with the function run? if so, should I do a delete [] Array inside the run function?
2. When I do delete[] pArray in main, what does it delete? memory for array[50]? or array[100]?
#include <iostream>
using namespace std;
void run(int* Array, int& s) {
s = 50;
Array = new int[s];
[Code] ....
Suppose I wished to reallocate memory (resize) an array of pointers. Why does the following not work?(The program runs, yet yields a faulty segmentation error message. Why?):
Code: char **ptrarr = (char**) malloc(sizeof(char*))
Code: ptrarr = (char**) realloc(ptrarr, (capacity) * sizeof(char*));
Code to allocate the memory for my arrays in the create array function.
#include <iostream>
#include <cstdlib>
using namespace std;
typedef int* IntPtr;
const int NUMLABS = 4;
[Code] ....
By using operator overloads i need to be able to * two dynamic arrays;
this is what i have so far
MyInt operator* (const MyInt& x, const MyInt& y) {
MyInt Temp;
int carry = 0;
if(x.currentSize > y.currentSize){
for( int i =0; i < y.currentSize; i++)
for(int j = 0; j < x.currentSize; j++)
[Code] ....
i was trying to make a dynamic array in this form :
int x;
cin>>x;
int ar[x];
my g++ (gcc) compiler on linux refused to create an array without a fixed size , however using the same code on windows on dev-cpp it was complied and executed , also it allowd me to create and use the dynamic array , i thought it was a compiler bug , however when i restarted and returned to g++ it compiled and executed the code although it never did before i tried the code on windows , how can that be and is it dangerous ?
Im trying to create a function that searches my array for a specific string, and then displays that string and the other content associated with it. I'm basically searching for a keyword within an array that has multiple strings with in each element.
View 4 Replies View RelatedI have recently bought a copy of "Jumping into C++" and have come to chapter 14 ( dynamic memory location) and have a question.
On page 153-154 an example of dynamic allocation is given for array's of int. How would the code look like for strings or structs ?
The allocation was given by:
Code:
int *growArray (int* p_values, int *size)
{
*size *= 2;
int *p_new_values = new int[ *size ];
for ( int i = 0; i < *size; ++i )
{
p_new_values[ i ] = p_values[ i ];
}
delete [] p_values;
return p_new_values;
}
Sample Code I tried to use this for an array of structs but failed completely....
I used the following struct Code:
struct user{
int days;
string name;
};
and the allocation function (which does not work):
Code:
struct user *growarray (struct user *p_values, int *size) {
*size *= 2;
struct user *p_new_values = new struct user[ *size ];
for ( int i = 0; i < *size; ++i )
[Code].....
Say I have a class called Play now I have a constructor called Play(int, char, int); I create Play play=new Play[2]()//default const Now i want to initialise different values of play objects using play(int char int) Whats the syntax? play[i](vale, value value); ? Its not working..
View 5 Replies View RelatedSo I'm trying to wrap my head around dynamic arrays, and I've finally figured out how to build one, using
int arraysize = randomnumber;
int* arrayname = new int[arraysize];
Now, how to delete the array. Can I free the whole array from any scope in my program using a simple line like delete arrayname;?
Also, since I'm working in heap, I can't rely on the debugger to show me when I'm doing something wrong, If I create a struct such as :
struct twoints {int one, int two};
and then try to create a dynamic array of said struct using
int arraysize = 5;
twoints* arrayname = new twoints[arraysize];
Am I basically creating an array of 5 two ints?
//is it the same as doing this?
twoints arrayname[5];
I have become overwhelmed an frustrated at these current operator overloads!
Currently I still can not get my +,* or istream operators working at all!
#include <iostream>
#include <cstring>
#include "myint.h"
[Code]....
I started to practice some C++. I use to program in C and a little C++. Anyway, I am writing code that creates a dynamic array. I would like to be able to do something like
galaxyobject[object] -> uniqueid = in the class but I do not think I have it setup right.
Question.
1. Is the code correct?
2. Why can't I use the above line without a compile error or segment fault?
int main() {
cout << "ProteusCore Server" << endl;
// create a galaxy system with a certain amount of objects
galaxy galaxysystem;
galaxysystem.IntializeGalaxy(100);
[Code] ....
I made the code available to see on sourceforge as Proteus 3d Game Engine. It is something I would like to work on.
Do I really need to create a separate pointer to point to dynamic arrays?
T* temp = new T[capacity_ * 2];
T* tIter = &temp; //Do these need to be here?
T* dIter = &data; //Or can I use *(temp + i) and *(data + i)?
(for unsigned int i = 0; i < size_; i++) {
*(tIter + i) = *(dIter + i);
}
We are supposed to create a menu with an option to add a car (make, model etc) to inventory. I have the structure format set up as far as adding the car, but I am stuck on how to make it a dynamic array of structures or whatnot (I'm not really sure on what I'm trying to do in the first place!) Basically, the user can choose to add a car and its info in. How do you set up the array to add whatever number of cars is needed? Will it be able to add more cars should the user come back to the program later?
This is the instruction of this portion of the project :
Menu Application
Add a car to inventory
Prompted to add
Make, Model and Year, Color, Miles, Price
Finish (adds the car to the file)
Cancel takes you to the main menu
I need to create subfunctions to do basic Matrix mathematics (addition, subtraction, etc.) I need to be able to pass bot of my Matrices to subfunctions. I started with the addition sub function and I cant get the code to run. I keep getting expected primary-expression before ']' token error for line 75.
#include <iostream>
#include <stdio.h>
using namespace std;
[Code].....
I cant get with part of it is wrong, i want to sum every row, too.
// Color Number.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include<conio.h>
#include<iostream>
[Code].....
So when if you want to change the values themselves for example in an array (just for example) this is valid;
void test(int* test)
{
test[0] += 10;
}
int bob[] {1, 3, 5};
If you did that bob[0] would not equal 11. All well and good right?
Now if you do this?
int sally = 33;
test(sallay);
This wouldn't work at all you actually have to use
void test(int& test)
{
test += 10;
}
how the memory addresses etc. are working here? I don't understand why you need to use & the reference operator if it's not an array? Why wouldn't that still work?