C++ :: Declaring And Accessing Arrays In Classes
Mar 31, 2013
We are learning how to use composition. In this project there is the Main (), resistor .cpp and .h, capacitor .cpp and .h, and filter .cpp and .h. I have 4 arrays built in the resistor.cpp that I want to print through the main(). I put the arrays in the constructor and have watched them initialize with the proper values, but as soon as the program leaves the constructor the values are wiped away and the elements are left with the value " -858993460 " in all of the them.
Here is the code:
Filter Main()
#include "Capacitor.h"
#include <conio.h>
#include "Filter.h"
#include <iostream>
#include "Resistor.h"
#include <windows.h>
#include <iomanip>
[Code] .....
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Jan 23, 2012
I'm picking up C++ by translating java code to C++. I have the completed code in java and it works perfectly. I'm not going to paste the whole code, this is a part of what I have:
Code:
class Graph
{
final int MAX_VERTS = 20;
[Code]....
I know it looks almost exactly the same as its java counterpart. I have several sources opened, but it's all bits and pieces of what I need.
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Feb 24, 2013
What is the general syntax for declaring two-way friendship in 2 classes?
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Feb 22, 2013
I have two classes, a Package class and a Person class. The Package class has two Person objects has member variables, a Sender and a Receiver. While overloading the << operator for the Package class so that it will make an output label from everything in the Package class. Here is my code...
class Package{
public:
Person Sender;
Person Reciever;
int weight;
double cost;
friend ostream &operator<<(ostream &out, Package &pack);
[Code] .....
So my problem is on that last output line, I am unable to call Sender.getName()... etc. Is there a proper syntax so that I can access the members of the Person class while overloading the << operator for the Package class?
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Oct 23, 2013
I'm just wondering, why you have to set the length of the inner arrays declaring a function. In which moment does the code needs to be sure about the length of the inner arrays accessing an cell?
I came up with this question realizing the elements of the outer array beeing pointers to the first value of each inner array. Therefore I can access e.g. the first first element of the second inner array like this:
**(arr + 1) ...regardless of the length of any array to my mind.
parallel post: [URL]...
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Apr 1, 2014
According to [URL] ....
" char myword[] = { 'H', 'e', 'l', 'l', 'o', ' ' };
char myword[] = "Hello";
In both cases, the array of characters myword is declared with a size of 6 elements of type char: the 5 characters that compose the word "Hello", plus a final null character (' '), which specifies the end of the sequence and that, in the second case, when using double quotes (") it is appended automatically."
However there are examples where word array is declared as :
char myword[] = { 'H', 'e', 'l', 'l', 'o' };
Is syntactically correct?? If yes, what is the size of myword? and does ' ' append by compiler automatically?
And is char myword[] = "abc" same as char myword[] = {'a','b','c',' '} or is it same as char myword[] = {'a','b','c'} ??
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Oct 23, 2013
i'm facing some problems with the array, as I have my .h and .cpp files so do i declare them as per norm of how we usually declare a function?
pointtwod.h
class PointTwoD {
private:
int xcord,ycord;
float civIndex;
LocationData locationdata;
[Code] ....
when i compile the error message i get was even when i i put in int xord[]; in my PointTwoD.h file:
PointTwoDImp.cpp:99:6: error: prototype for 'void PointTwoD::storedata(int*,int*,float*) does not match any in class 'PointTwoD'
PointTwoD.h:48:8: error: candidate is: void PointTwoD::storedata(int, int, float)
PointTwoDImp.cpp: 135:22: error: 'xord' was not declared in this scope
PointTwoDImp.cpp: 135:27: expected primary-expression before ']' token
PointTwoDImp.cpp: 135:30: error: 'yord' was not declared in this scope
PointTwoDImp.cpp: 135:35: expected primary-expression before ']' token
PointTwoDImp.cpp: 135:38: error: 'civ' was not declared in this scope
PointTwoDImp.cpp: 135:42: expected primary-expression before ']' token
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Feb 9, 2013
I'm creating a program to read information about class schedules at my school, reformat the information, and allow the user to search for specific semesters. There are eight fields of information. I'm reading the info from a text file using eight parallel arrays, but I'm having trouble declaring the arrays. I can run this code in one compiler (Dev-C++) with no problems, but I get errors when trying to compile it using Visual Studio stating that arrays must be declared with a constant value. I have a loop to run through the text file, with a counter to increment with each subsequent line, then I create a constant int equal to the counter, and declare the arrays of size equal to the constant int. Here's the section of code in question:
// Counting the number of lines in the text file
inFileForLines.open("CIS225HW1DA.txt");
string countLine;
int numberOfLines = 0;
//Discarding the first line of the text file containing only column headings
getline(inFileForLines, countLine);
[Code] .....
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Aug 30, 2013
I came across the below code snippet in a project and was not sure how value of variable "response" is computed. Here as we can see, pic_data holds two one dimensional arrays but "response" access both the single dimensional array as two dimensional array.
Code:
#define MAX 100
#define MAXBUF 100
u32 response;
u32 index;
}
[code]....
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Aug 31, 2014
How do i access the private array? I tried this and it's not working. Want i want to do is create class object in main and pass the string to constructor, and set m_make, m_model to that string. Then call the member function to output that.
const int BUFLEN = 256;
// class declaration
class CVehicle
{
[Code].....
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Feb 9, 2014
I'm confused about accessing elements from arrays. Supposed I have an array of pointers to char:
char *names = { "John", "Rose", "Steven" };
To access one of the strings, should I use names[ 0 ][ i ], where i is an index in the set ( 0, 1, 2 ), or should I use names[ i ]? I would think it would be the first option, because this array has 1 dimension that contains others arrays, right?
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Mar 1, 2014
I'm working on a project where I have the user enter storm data about hurricanes for multiple seasons. I need to make separate arrays for:
1. the month, wind speed, and min. press.
2. the category of the storm
What I'm having trouble understanding is how to make the software take an input, assuming from a scanf, and put it in an array. Then taking that value and output-ing it back out when needed.
So here is piece of my code. Note: Disregard the commented sections of the code, my current project is building off a previous one, where in the last project we were using loops, now we are using arrays.
case 1:
{
if (year > 0) //begins counting
{
/*num_trop_storms = 0*/ num_hurricanes = 0, year = 0, wind_speed = 0,
hcat1 = 0, hcat2 = 0, hcat3 = 0, hcat4 = 0, hcat5 = 0, hrun = 1, totalhurr = 0;
knots = 0, cummwindspeed = 0.0;
[Code] ....
In the code above, how exactly the scanf takes the inputs from the user and then stores them for me to access. So, I want my array to be 3 columns, for months , wind_speed, & minpress. The array has a undetermined amount of rows. I think if I figure out the first array, I can handle the second.
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Jun 26, 2014
Here's the problem. I want to generate an array of objects from classes.
brick[] tile = new brick[5] // originally wanted an array of 500 to play with but I thought I'd start small first
I wanted to make a draw() function in my "level01" class to generate a map (so I wouldn't have to build them in photoshop then manipulate rectangle bounding boxes). I tried several things...
First, I found a thread that worked to get rid of the null value in the array ("not set to reference of an object" error).
After that, within a for loop, I tried to initiate my values...
for (int i=0; i < tile.Length; i++) {
tile[i] = new brick(); // calling the object
piece[i] = new PictureBox(); // calling the object's container
//tile[i].brick1X = 38; // already had a default set to it so I commented this out to see if it made
// any difference... it didn't
tile[i].brick1Y += 32; // if this worked, it would have drawn a 32x32 tile down the Y axis every 32
// pixels
[Code] ....
In my Form.cs, I declared my first level map as:
level01 L01 = new level01();
Under the form's constructor, I instructed it to
L01.draw();
so that it would initiate on the game screen.
Needless to say, I get the game screen and the frame, the menu bar I have pops up. But, no tiles.
I even went so far as to get rid of the null values for [i] in the array (using the above for loop but with fewer tasks within the loop) and created a counter that would count up += 1 every time it would make an object.
if (counter < 5) {
And would put in the above tasks inside of the logic loop. I would either get nothing drawn on the screen or it would throw an exception.
I could easily make this using XNA Game Studio in Visual Studio 2010 but I'm using VS2013 and wanted to do a program straight in C# instead of using XNA.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.Windows.Forms;
[Code] ....
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Apr 12, 2013
A company uses two text files: one to store employees' details and another to log their sign in/out time.
The details file - called details.txt" has the following format: ID, Name, Date of Birth, SSN, Department, Position - separated by spaces.
An extract from the file looks like this:
10 alice 4/23/1972 123-45-6789 support assistant
3 bob 6/7/1980 111-12-1134 logistics manager
1 carol 10/2/1963 987-123-1143 admin ceo
2 dave 10/3/1974 902-22-8914 admin cfo
17 erin 6/13/1991 126-83-1942 technology supervisor
15 frank 2/22/1987 303-12-1122 logistics assistant
"timelog.txt" contains daily logs of when employees arrive and leave. It has the following format: ID, Date, Arrival Time, Departure Time - separated by spaces. An extract from the file looks like this:
10 2/11 0900 1700
3 2/11 0930 1730
1 2/11 1100 2000
2 2/11 1000 1530
17 2/11 0900 1700
10 2/12 1000 1830
3 2/12 0930 1730
1 2/12 1100 1900
2 2/12 1030 2000
17 2/12 0900 1700
15 2/12 1100 1600
I have to write a program that searches for specific records using some search parameter, and displays them. Ok first i have to read the data from the files and store them. this is what i have so far....
#include <iostream> //Accesses libaries for console input and output
#include <fstream> //Needed to access the fstream object to read files
#include <string> //Needed to access the string class
#include <cstdlib>
[Code] ....
I know my class and array code is totally wrong i dont know how to store the data for the info is in integer and string form... do i use strings, arrays?
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Oct 5, 2013
I have an array of (Student)classes created in Manager.h, which contains a new instance of class Name (name),(in Student.h)How would I go about accessing the SetFirstName method in Name.cpp if I was in a class Manager.cpp? I have tried using Students[i].name.SetFirstName("name");
// In Manager.h
#include"Student.h"
class Manager
{
[Code]....
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Nov 6, 2014
I am putting a instance o the Vehicle Class inside the constructor of the Calculate Class then calling it later. I get a warning saying the variable is not used and a error when I try to used the functions from the vehicle class saying use of undeclared identifier.
Code:
#include <iostream>
#include "Calculate.h"
#include "Vehicle.h"
#include <fstream>
Calculate::Calculate(){
[Code] ....
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Jun 5, 2013
I am a bit confused about how specific one must be with arguments when declaring a function. I'll show you two functions from the book I'm using to learn C to show you what I mean.
Example 1 (greatest common denominator function):
Code:
void gcd (int u, int v) {
int temp;
printf ( "
[Code] ....
So in that function, there are exactly two arguments, because that's how many arguments the algorithm to find the gcd takes. No problem there, makes sense to me. Then further in the chapter on functions I run into this,
Example 2 (square root function):
Code:
float absoluteValue (float x) {
if ( x < 0 )
x = -x;
return x;
[Code] ....
In this second example, we have a square root function that is preceded by an absolute value function. The absolute value function has the one argument, "float x", however when this function is called within the square root function, the arguments "guess * guess * -x" are passed to it. I'm confused how this absolute value function is working with all of that inside it, when it was originally declared with just "x." The only possibility I can think of is that this expression is treated as a single unit, but I'm not sure.
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Apr 4, 2013
Code:
if (IS_LEAP_YEAR(year))
const int days_per_month[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
else
const int days_per_month[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; Is it ok to declare the array in this manner or is it bad?
And i have to ask the user for a date to enter in my program. So should I use scanf or should I store the date in a string and then use sscanf. I have to check for valid input for everything like day, month, year etc. I did it as below..
Code:
int assignments;
assignments = scanf("%d / %d / %d", &month, &day, &year);
fflush(stdin);
if (assignments != 3)
{
printf("Retry: ");
}
else
error checking.
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Aug 1, 2013
Code:
#include <stdio.h>
int main(void){
int a=0;
for(;a<=10;)
int b;
return 0;
}
I have got a code like this. I don't expect to get an output but just assumed I would see the command screen until I terminated it. What I want to do is just declare a variable b in a endless loop. But what I got from the compiler is this error: error: expected expression before 'int'. I am using Code::Blocks and I think the compiler is GCC.
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Jun 13, 2014
I'm using some rather large external libraries, and I want to load them in my .cpp file only. so, my header looks like this:
namespace {
// hidden declarations
namespace geometry {
class Point;
class Polygon;
class Box;
//etc
}
}
In the declaration of the main class in that header, I merely use these as pointers or references. The .cpp file looks as follows:
// Boost
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
[Code] .....
This doesn't work however:
error C2371: '`anonymous-namespace'::geometry::Point' : redefinition; different basic types
1> e:..........NavigationMesh.h(10) : see declaration of '`anonymous-namespace'::geometry::Point'
What can I do to forward declare external classes like this?
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Jun 30, 2014
We have been assigned to create an iTunes library. Everything compiles in my other .h file but my main is not happy with my object declaration. It keeps stating "primary expression before '{'". Here is my main code:
#include<iostream>
#include<string>
#include<fstream>
#include"myTunes.h"
using namespace std;
//function protocols
void read(string);
[Code] ......
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Mar 18, 2013
I'm writing this program that basically interprets the rottentomatoes website. I am however having a problem declaring if it is rotten or fresh according to the rating the user enters.
I'm outputting it here:
void PrintAll(const string titles[], const int ratings[], int count) {
WriteLine('=', 50);
cout << "PRINT ALL" << endl;
WriteLine('-', 50);
[Code] .....
And here is my condition:
string RatingToString(const int ratings[], int count) {
string rank;
for(int i = 0; i < count; i++) {
[Code]....
Here is the output:
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950
==================================================
MENU
1. Add Movie
2. Print All
3. Exit
--------------------------------------------------
Enter 1-3 : 1
Title : Hitch
Rating : 90
==================================================
[Code]....
My condition works when there is only one movie, but when I add more, it gives it the new movies "ROTTEN" or "FRESH" rank.
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Sep 26, 2014
Is it permissible to declare, for example, `std::valarray<int&>`? If so, how do I initialize such if the `valarray` is a class member?
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Oct 29, 2013
I have the following code:
struct mystruct {
char fieldA[5];
char fieldB[7];
};
void dosomething(struct mystruct* pms) {
[Code] ....
Is there any problem doing that, even for a C89/90 compiler?
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Oct 21, 2012
I can not set the size of my array while running porgrama. Is there any way to do this in C + +?
---- code ------
#include <iostream>
#include <string>
using namespace std;
[Code].....
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Sep 9, 2014
see these sample:
Code:
#include <iostream>
#include <string>
using namespace std;
class test{
public:
virtual void ola() {
[Code] .....
Like you see, i don't re-declare the 'ola' function in 'test1' class, only in 'test' class. The compiler tell me the 'ola' isn't member of 'test1'. in 'test' i put it 'virtual', but forgetting that, how can i override it without re-declare it?
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