I've been given specific instructions to create an array inside a Class Matrix using a constant n. This is my class but I am getting errors. I thought that maybe I had to initialize the const and the array using the constructor function Matrix() instead of directly in the class, but I didn't have any luck with that either.
class Matrix
{
public:
Matrix();
private:
const int n=3;
int e[n][n];
};
I wanted to add that the template argument is needed because its a "special case" but if that doesn't work what would be the next best way to solve this problem. I want to be able to declare the const size of the array outside the class far removed from it actually. I'm actually going off this page
[URL] .....
Heres the code
#include <iostream>
template <int F>
class C
{
[Code]....
Please consider the following code :
#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
At the moment I am making program that will use a 2d selection of "cells" to make a "map" of sorts. However, the size will not be known until run time.
I figured using an array would good, because once the size is chosen it won't be changed. However I can't create an array without using a constant.
So the first question is, can I create a constant at run-time with a user entered value that can then be used for an array size? If so, how?
Otherwise, what are my options to achieve this? I know vectors can be used, but A, my compiler keeps giving me problems even when C&P some code bits (yes I even remembered to #include and such) and B, I noticed that vectors reserve extra memory for when the size changes but this is bad (well my dinky little program won't notice, but trying to set good habits as I learn, so I'm keeping it in mind) as I don't need and don't want to allow the size to change after creation.
Which leads to number three, if I do have to use vectors, how can I prevent any accidental size changes after the initial size is determined?
Define a constant PI that has a value of 3.14159
- Create a double variable, Radius with an initial value of 10
- Create two double variables. Circum and Area, without initialization
- Using the following formulas, compute circumference and area of the circle:
circumference = pi * r * 2 (here, r means radius)
area = pi * r * r
- Display the result using three variables (numbers must come from variables)
- Expected output: (Don’t forget to display the period at the end of the first line)
Circle with radius of 10.
Circumference = 62.8318 Area = 314.159
I'm trying to create a program that will play scales at certain frequencies, but my arrays are not initializing correctly. I've read up to double check what i'm doing but it doesn't seem to be working. My only guess is my use of a global variable.
const int NotesInScale = 8;
class Scales {
private:
//all Major Scales
int CMajor[NotesInScale];
int GMajor[NotesInScale];
[Code] ....
i'm simply trying to put the frequencies in the scales (the numbers in the array) but I keep getting an error. I feel its a simple fix but i'm not seeing it.
I've written this class and struct to create a singly linked list. The data is stored in the binary file which I've opened and read. I'm trying to load said data into a class type array. The errors I'm getting are "incompatible types in assignment of 'StatehoodInfo' to char[3]" Lines 130-134 is what I was working on.
#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <string>
#include <cstring> //For char[] string functions
[Code] .....
My Fraction.h class looks like :
class Fraction {
int num;
unsigned int den;
public:
Fraction(int = 1,int =1);
//Constants of Datatype
[Code] ....
The implementation Fraction.cpp is as follows :
#include "Fraction.h"
Fraction::Fraction(int n, int d):num(n),den(d){
cout << This is double param constructor <<endl;
}
And the application main.cpp is
int main(){
Fraction f1(3,9);
f1 = Fraction::sc_fUnity; // how to implement this ?
}
How can I write the Fraction.cpp for the constant static member ?
I would like to have a unmodifiable standard of WAVEFORMATEX defined as a member of a class of mine. Something like:
class InputTest {
public:
const WAVEFORMATEX StandardWaveFormat;
public:
void TakeInput(WAVEFORMATEX pFormat);
};
Then in my cpp file to hard-code the values:
WAVEFORMATEX InputTest::StandardWaveFormat {
//Instantiate WaveFormat -- PCM standards
StandardWaveFormat.wFormatTag = WAVE_FORMAT_PCM;
StandardWaveFormat.cbSize = 0; //extra information sent over stream. Usually ignored in PCM format.
[Code] ....
I get the following errors starting with the header file:
Error1error C2146: syntax error : missing ';' before identifier 'StandardWaveFormat'
Error2error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
both associated with the "const WAVEFORMATEX StandardWaveFormat; " line.
Here's a link to the WAVEFORMATEX struct: [URL] .....
Then the cpp source code is probably way off. Let me know if you'd like to see the errors associated with that.
I wrote a template class for Matrix manipulation. The compiler cannot compile the source and complains
Matrix.h:144:41: error: expected initializer before ‘const’
What is the problem of the code enclosed below?
#ifndef MATRIX_H
#define MATRIX_H
/**
* @file Matrix.h
*The Matrix template class written for simplify the matrix manipulation.
*/
#include <cassert>
using namespace std;
template<typename T>
class Matrix {
int rows,cols;
[Code] .....
Can distinguish between character constant and string constant giving examples
View 1 Replies View RelatedSuppose I have two classes A and B so how to access object of class A in constructor of B's class as a parameter.
View 6 Replies View RelatedThis is going to seem like a stupid question but how can I count the elements of a const array. Surely c++ compilers provide a count for const arrays?
const wchar_t* ItemHandler::itemNames[] = {L"Coins", L"Matches"};
const wchar_t* ItemHandler::itemIconLocations[] = {L"./media/Items/coins.png" , L"./media/Items/matches.png"};
const bool ItemHandler::itemStackable[] = {1, 1};
I want to count the elements so if the server sends a bad item id it won't crash every client in range lol. I heard that the sizeof keyword returns the size of the array in bytes. I used to think the size of keyword would return the element count but found out it isn't.
I have the following code:
Code:
unsigned int bh = 3;
unsigned int b= 2*bh+ 1;
float s[b];
I get the following 3 compilation errors:
error C2057: expected constant expression
error C2466: cannot allocate an array of constant size 0
error C2133: 's' : unknown size
I am using Visual Studios 2010. What is wrong?
I have this code:
const BYTE original[2][4] = {
{0x00, 0x00, 0x00, 0x00},
{0xFF, 0xFF, 0xFF, 0xFF}
};
void function(const BYTE** values){
[Code] ....
You might notice that the above code doesn't compile, this is the error:
cannot convert parameter 2 from 'BYTE [2][4]' to 'BYTE *'
1>
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
Even after some search I couldn't really find an answer to my problem, how do I pass the const BYTE array which I declared above in the function as a parameter (or what structure do I need to set for the function as a parameter)?
This is my coding so far and I am confused to what the constant for array size is
//initialize arrays
string states[ARRAY_SIZE]={"Alabama", "Alaska", "Arizona"};
string capital[ARRAY_SIZE]={"Montgomery", "Juneau", "Phoenix"};
while (play again) {
//generate random index number
int index = rand () % _______
what goes after the rand () % ?
I'm currently reading the C++ Guide for Dummies
Anyway right now I'm working with pointers and classes, and when I create a new pointer for my class it looks like this...
Pen *Pointerpen = new Pen;
But in the book they threw in this...
Pen *Pointerpen = new Pen();
Can you actually designate memory space for a function? Or was this a typo on their part? It's never come up before and they didn't explain it.
I was trying to implement own vector class and wrote some code. Below is the code.
Code: #include<iostream>
#include<vector>
using namespace std;
template <typename T> class MyVector
{
T *mem;
int m_size,final_size;
public:
MyVector() : final_size(1),m_size(4)
{
[code].....
I have question on this function.
Code: myVecPush_back(T t){}
Here I was able to put elements upto any number of time, but I have allocated memory to only 4 elements in T *mem.
My question, why the program is not crashing when I tried to put elements more that 4?
Is since the variable is of type Template? Any specific reason for this?
I am currently working on a "bag" class which is sort of a common sense answer to creating a random class with difference functions. I am attempting to create a "union" function which takes two bags ie: bag1 and bag2, adds all the items in both bags and creates a new bag ie: "bag3". For some reason I keep coming up with problems instead of solutions. Maybe it's the fact I just got done with 2 days of calculus. I don't know. My code is below. Both a main(source) and header file.
Header
#ifndef BAG_H
#define BAG_H
const int BAG_CAPACITY = 20;
template <typename T>
class Bag {
private:
int count; // Number of items in the Bag
[code]....
I have a background in c# and am very frustrated with c++. If I created a class in c# like so:
public class Memory{
int x = 0;
int y = 0;
int height = 0;
int width = 0;
string firstname = "Bob";
string lastame = "Chester";
}
and then created a new instance of this class from a separate class by doing:
public class Main{
Memory mem = new Memory();
}
I have raked the internet for a way to create a new instance of a class in c++ while keeping its default values and have come up empty handed.
I've just recently moved from Visual Basic 6 over to C++ and decided that I would try and write a class to mimic the Get/Set behavior seen in a variety of other programming languages. So instead of just using an overloaded function, i.e:
Code:
class NoProp {
LPCWSTR m_Title;
public:
void Title(LPCWSTR NewValue) {m_Title = NewValue;};
LPCWSTR Title() {return m_Title;};
[code].....
So far this code only works with the LPCWSTR type (const wchar_t*). Unfortunately I got to this stage using only that type, and now when I try another type, such as int, it fails. When using the int type I believe it creates an error because the constructor of InitProp expects a type of pointer to be parsed. When I try using it with int* type (the private variable then becoming int **m_Variable) it compiles, thought I cannot access the property like a normal int.
My best guess from here is that I probably have to overload the InitProp constructor in a way that it can setup the Property classes for base-types and pointer-types, and then also modify the Property class to handle both.
I have defined a class in a header file; just the class, no templates involved. I have a program where I'm reading in data in string format. Each string consists of a word, a delimiter, and a variable name. Example:
cajun/mustard
I want to take that string and make it the variable name of that class type. It would be implemented along the lines of:
Code:
string str;
//read/process string here, get:
str = "mustard";
createName(str);
//pass string to creator function When the function is called, I should get the variable:
Class mustard;
Thing is, I'm not supposed to know beforehand what the variable names are, only that I create them as they are read in. It could be mustard, it could be Maynard_James_Keenan, it could even be bazinga.
My problem is, what do I do for createName()? I've looked into the concepts of pairing, Factory implementation, and maps, but I don't think they answer my question.
(P.S. if I run into the same variable name being read in twice, what steps can I take to make sure that a duplicate variable isn't created? Do I need to add in code, or does the compiler know to watch for multiple variables of the same name?)
Creating the methods for class List
main.cpp Code: #include "List.h"
int main( )
{
List la; // create list la
la.push_front( "mom" );
la.push_back( "please" );
la.push_back( "send" );
la.push_back( "money" );
la.push_front( "hi" );
cout << "
la contains:
" << la << '
[code]...
I recently posted a question related to creating a heap template class. The ultimate goal is to create a series of classes that serve a purpose that was overlooked in the Qt library that I need for my current project.
The current "end goal" is a PriorityQueue template that uses a comparer class which is inherited from a "template interface". Basically a pure virtual class template. Perhaps that is the mistake to begin with but hopefully not. (Is this a valid approach?)The problem I am getting is that when I compile the code, it says my derived comparer class is abstract.
I will include all related classes here. I doubt it is relevant but the templates and the classes based off them are in different namespaces.Here is the comparer "template interface":
// in global namespace
template<class T>
class IIMQOBJECTS_EXPORT IQComparer {
virtual int compare(T& a, T& b) = 0;
virtual bool equals(T& a, T& b) = 0;
virtual bool isGreaterThan(T& a, T& b) = 0;
virtual bool isLessThan(T& a, T& b) = 0;
};
Here is the class that is supposed to be non-abstract but isn't recognized as such:
// in the application namespace AND IN SAME project that has the NetEventInfo class
// all functions ARE defined/implemented in a cpp file
class APPCORE_EXPORT NetEventInfoComparer : ::IQComparer<NetEventInfo*> {
public:
NetEventInfoComparer();
~NetEventInfoComparer();
[code].....
Let's say I reference a dll in my project that has an abstract class in it:
public abstract class Module {
public string type;
public abstract string doSomething();
}
And then I have an Assembly object, loaded from a dll that is not referenced in project, but rather loaded during run-time, containing:
public class Tester : Module
{
public static string type = "Test";
public override void doSomething() {
//Stuff being done
return "hello";
}
}
How can I get the value of "type" in the class that is loaded during runtime? How do I use the "doSomething" method of it and get the returned object?
The only difficulty im having is creating a class and methods & being able to access them from my win form app. Can i get a few tips on the do's and donts of creating classes / methods and accessing them from form app.
This is what i have put together so far.
public partial class Form1 : Form {
private Image[] dicePics;
private int[] diceNum;
private Random randomize;
public Form1() {
InitializeComponent();
[code]....