Program stops working, pointer error i'm sure - c++

I have this program, and I'm still getting used to C++ pointers, so It's probably an issue with that. But I am having the program crash when the getStructData() function is called. I've probably messed up something to do with the pointer to the struct that i've used, but I'm really not sure at this point. Any tips or help are appreciated. Thanks, and before people start the mad downvoting, this isn't a homework assignment from my school, I'm just going over other schools homework to practice during the christmas break.
Prog1Struct.h
#ifndef INCLUDED_PROG1STRUCT
#define INCLUDED_PROG1STRUCT
struct Prog1Struct
{
int m_iVal;
double m_dArray[5];
char m_sLine[80];
};
#endif
Prog1Class.h
#ifndef PROG1CLASS
#define PROG1CLASS
#include "Prog1Struct.h"
class Prog1Class
{
private:
Prog1Struct myStruct[5];
public:
/*Prog1Class();
~Prog1Class();*/
void setStructData();
void getStructData(int structureArrayIndex, struct Prog1Struct *info);
void printStruct(int indexPriv);
void printData();
};
#endif
Prog1Class.cpp
#ifndef INCLUDED_PROG1CLASS
#define INCLUDED_PROG1CLASS
#include <iostream>
#include <string>
#include "Prog1Class.h"
#include "Prog1Struct.h"
#include <time.h>
using namespace std;
void Prog1Class::setStructData()
{
for (int i = 0; i<5; i++)
{
cout << "Enter an integer: ";
cin >> myStruct[i].m_iVal;
for (int j = 0; j < 5; j++)
{
cout << endl << "Enter a double: ";
cin >> myStruct[i].m_dArray[j];
}
cout << endl << "Enter a string: ";
cin.ignore(256, '\n');
cin.getline(myStruct[i].m_sLine, 80, '\n');
cout << endl;
}
}
//takes in index for array, and pointer to a struct of the type in Prog1Struct.h. Copies all data from the private struct at the given index into the struct of the pointer argument.
void Prog1Class::getStructData(int structureArrayIndex, struct Prog1Struct *info)
{
*info = myStruct[structureArrayIndex];
cout << "Printing *info from getStructData function" << endl;
cout << info;
}
void Prog1Class::printStruct(int indexPriv)
{
cout << myStruct[indexPriv].m_iVal << " ";
for (int k = 0; k < 5; k++)
{
cout << myStruct[indexPriv].m_dArray[k] << " ";
}
cout << myStruct[indexPriv].m_sLine << " ";
}
int main(void)
{
Prog1Class c;
Prog1Struct *emptyStruct = '\0';
cout << "setStructData called:" << endl;
c.setStructData();
cout << "getStructData called:" << endl;
//error comes here, at getStructData.
c.getStructData(2, emptyStruct);
cout << "printStruct called:" << endl;
c.printStruct(2);
cin.get();
}
#endif

You are trying to assign a value to a null pointer.
Prog1Struct *emptyStruct = '\0';//set emptyStruct to 0 (This means it points at address 0, not holding a 0 value)
cout << "setStructData called:" << endl;
c.setStructData();
cout << "getStructData called:" << endl;
//error comes here, at getStructData.
c.getStructData(2, emptyStruct);//emptyStruct is still = 0
So in the function, info = 0.
void Prog1Class::getStructData(int structureArrayIndex, struct Prog1Struct *info)
{
*info = myStruct[structureArrayIndex];//This line is trying to write to a section of memory you don't have access to (address 0)
I think you want this instead. (untested) This will make info point to myStruct[structureArrayIndex] (Not copy the contents of myStruct[structureArrayIndex] to info). Pointers only point to things (like structs or some other type), they cannot contain a struct.
info = &myStruct[structureArrayIndex];

Related

Semantic error in the selection condition of the type of LED lamps

I have a class of light bulbs. There are methods and constructors in this class. There is even a destructor) The problem is that I have to determine and display information about class members with type "n" in the TEST() method (LED lamps).
To implement this task, he developed the gettype() method, which returns the type of an object, and, in fact, the TEST() method, which displays information about light bulbs.
The problem is that nothing works for me. I tried a lot of things, but it doesn’t work out for me to implement this task. I'm new to programming (
Code:
#include <iostream>
using namespace std;
class lamp
{
public:
// methods
void TEST(void);
char* gettype (void);
void INIT(void);
void SHOW(void);
// construcrors
lamp();
lamp(const char *t, int powe, const char *c, double cos);
lamp(const lamp & obj);
// destructor
~lamp();
private:
// data
char type[100]; // LED, energy-saving or incandescent lamp
int power; // LED lamp - "n"
char color[100];
double cost;
};
lamp::lamp() {
cout << "This object was created in the default constructor.\n";
strcpy(type, "");
power = 0;
strcpy(color, "");
cost = 0;
}
lamp::lamp(const char *t, int powe, const char *c, double cos) {
cout << "This object was created in the constructor with parameters.\n";
strcpy(type, t); //*t
power = powe;
strcpy(color, c); //*c
cost = cos;
}
lamp::lamp(const lamp & obj) {
cout << "This object was created in the copy constructor.\n";
strcpy(type, obj.type);
power = obj.power;
strcpy(color, obj.color);
cost = obj.cost;
}
lamp::~lamp() {
cout << "Deletion of object by destructor.\n";
}
void lamp::SHOW(void) {
cout << "Lamp Information:\n";
cout << "\nType > " << type;
cout << "\nPower > " << power;
cout << "\nColor > " << color;
cout << "\nCost > " << cost << endl;
}
void lamp::INIT(void) {
cout << "Enter lamp information:\n";
cout << "\nType (if LED, then n) > "; cin >> type;
cout << "\nPower > "; cin >> power;
cout << "\nColor > "; cin >> color;
cout << "\nCost > "; cin >> cost;
}
char* lamp::gettype (void) {
return type;
}
void lamp::TEST(void) {
cout << "\nType > " << type;
cout << "\nPower > " << power;
cout << "\nColor > " << color;
cout << "\nCost > " << cost << endl;
}
void main() {
setlocale(0, "");
// default constructor for 1 class instance
lamp l1;
cout << "Entering data for the first product." << endl;
l1.INIT();
// constructor with parameters for 2 class instances
cout << endl << "Information about the second object: \n";
lamp l2("n", 950, "yellow", 1580);
// copy constructor for the third object
cout << endl << "Information about the third object: \n";
lamp l3(l2);
// Derived information about all the lamps using the method SHOW
l1.SHOW();
l2.SHOW();
l3.SHOW();
// I create an array of two objects using the default constructor
lamp la[2];
I enter data into an array of objects using the method INIT
cout << "Fill an array of objects with 2 elements." << endl;
for(int i = 0; i < 2; i++) {
la[i].INIT();
}
// I output data from an array of objects using the method SHOW
cout << "Showing items." << endl;
for (int i = 0; i < 2; i++) {
la[i].SHOW();
}
// looking for and displaying information about LED lamps
cout << "Search and display information about LED lamps." << endl;
for (int i = 0; i < 3; i++) {
if (la[i].gettype() == "n") {
cout << endl << " lamp number : " << (i + 1) << endl;
la[i].TEST();
cout << endl;
}
}
system("pause");
}
There are several errors in your code:
strcpy is included in <cstring> which is missed. You need to add it in the beginning:
#include <cstring>
main() function should be declared as int main() and you need to add a return statement
int main() {
//YOUR CODE HERE
return 0;
}
You missed a comment sign at line 104
lamp la[2];
//I enter data into an array of objects using the method INIT
cout << "Fill an array of objects with 2 elements." << endl;
After fixed, your code should be able to run.

c++ vector of structs inside class

hello all i am working on a school prject called inventory inquisitor. the specifications are as follows:
enter image description here
so far i have created a class in which contains a struct and a vector of this struct.
all im trying to do so far is get the class to display the struct just to know it works but when i compile it and run it nothing happens. here is the code. excuse whatever rookie mistakes i have made i am very new with classes, and vectors. thanks you in advance!
//Inventory Inquisitor.cpp
#include <iostream>
#include <string>
#include <cctype> //for toupper
#include <fstream>
#include <vector>
using namespace std;
class Inventory
{
private:
struct item
{
string Description = " ";
double Quantity = 0;
double Wholesalescost = 0;
double Retailcost = 0;
string Dateadded = " ";
};
vector<item> Inv;
public:
void Display();
};
void Inventory::Display()
{
Inv[0].Description = "english";
Inv[0].Quantity = 1;
Inv[0].Wholesalescost = 100;
Inv[0].Retailcost = 200;
Inv[0].Dateadded = "3/8/2018";
cout << Inv[0].Description << endl;
cout << Inv[0].Quantity << endl;
cout << Inv[0].Wholesalescost << endl;
cout << Inv[0].Retailcost << endl;
cout << Inv[0].Dateadded << endl;
}
int main()
{
Inventory inst1;
inst1.Display();
}
You have to put something into the vector before accessing it:
// Create an item
item i;
i.Description = "english";
i.Quantity = 1;
i.Wholesalescost = 100;
i.Retailcost = 200;
i.Dateadded = 3/8/2018;
// The vector is empty, size() == 0
// Add it to the vector
Inv.push_back(i);
// Now the vector has 1 item, size() == 1
// Now you can print it
cout << Inv.at(0).Description << endl;
cout << Inv.at(0).Quantity << endl;
cout << Inv.at(0).Wholesalescost << endl;
cout << Inv.at(0).Retailcost << endl;
cout << Inv.at(0).Dateadded << endl;
According to your assignment, you will most likely change to function to print an existing item. You will have another function to add items to the vector.
void Inventory::Display(int index)
{
// Print an item already in the vector
if (index >= 0 && index < Inv.size()) {
cout << Inv.at(index).Description << endl;
cout << Inv.at(index).Quantity << endl;
cout << Inv.at(index).Wholesalescost << endl;
cout << Inv.at(index).Retailcost << endl;
cout << Inv.at(index).Dateadded << endl;
}
}

C++ Using array and for loop to output from multiple classes

I am asked to do this code and i need to use array or something similar to print out different classes. The only way i know is individually doing every single class is there a faster way of doing this. Following is the way i am using at the moment.
Ground_Transport Gobj;
Air_Transport Aobj;
Sea_Transport Sobj;
Car Cobj;
Train Tobj;
Bus Bobj;
Gobj.estimate_time();
Gobj.estimate_cost();
cout << Gobj.getName() << endl;
Bobj.estimate_time();
Bobj.estimate_cost();
cout << Bobj.getName() << endl;
Sobj.estimate_time();
Sobj.estimate_cost();
cout<<Sobj.getName()<<endl;
Aobj.estimate_time();
Aobj.estimate_cost();
cout << Aobj.getName() << endl;
Cobj.estimate_time();
Cobj.estimate_cost();
cout << Cobj.getName() << endl;
Tobj.estimate_time();
Tobj.estimate_cost();
cout << Tobj.getName() << endl;
Transport_KL_Penang Kobj;
cout << Kobj.getName() << endl;
This is the header file Transport_KL_Penang
#include <iostream>
#include <string>
using namespace std;
class Transport_KL_Penang
{
public:
Transport_KL_Penang() {}
virtual string getName() {
return Name;
}
int Time_in_hours1 ;
int Time_in_hours2 ;
int Cost_in_RM1 ;
int Cost_in_RM2 ;
void estimate_time() ;
void estimate_cost() ;
private:
static string Name;
};
void Transport_KL_Penang::estimate_time()
{
cout << "It takes " << Time_in_hours1 << "-" << Time_in_hours2 <<
" hours if you use " << Name << endl;
}
void Transport_KL_Penang::estimate_cost()
{
cout << "It will cost around " << Cost_in_RM1 << "-" << Cost_in_RM2 <<
"RM if you use " << Name << endl;
}
If you don't need a specific object name, you can write something as a code below, creating a multiples generics objects:
#include <iostream>
#include <cstdlib>
#include <time.h>
class Myclass {
private:
int randTime;
float cost;
public:
void estimate_time(){
randTime = rand()%100;
}
void estimate_cost(){
cost = randTime * 0.2;
}
float getEstimateCost(){
return cost;
}
};
int main(){
srand(time(NULL));
int numberOfObjects = 7;
Myclass obj[numberOfObjects];
//input
for(int i = 0; i < numberOfObjects; i++){
obj[i].estimate_time();
obj[i].estimate_cost();
}
// printing
for(int i = 0; i < numberOfObjects; i++){
std::cout << obj[i].getEstimateCost() << std::endl;
}
return 0;
}

Error Variable is Protected

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
using namespace std;
void armySkirmish();
void battleOutcome();
string commander = "";
int numberOfHumans = 0;
int numberOfZombies = 0;
class ArmyValues
{
protected:
double attackPower;
double defensePower;
double healthPoints;
public:
void setAttackPower(double a)
{
attackPower = a;
}
void setDefensePower(double d)
{
defensePower = d;
}
void setHealthPoints(double h)
{
healthPoints = h * (defensePower * .1);
}
};
class Zombies: public ArmyValues
{
};
class Humans: public ArmyValues
{
};
int main(int argc, char ** argv)
{
cout << "Input Commander's Name: " << endl;
cin >> commander;
cout << "Enter Number of Human Warriors: " << endl;
cin >> numberOfHumans;
cout << "Enter Number of Zombie Warriors: " << endl;
cin >> numberOfZombies;
armySkirmish();
battleOutcome();
return 0;
}
void armySkirmish()
{
cout << "\nThe Humans tense as the sound of the undead shuffle towards them." << endl;
cout << commander << " shuffles forward with a determined look." << endl;
cout << "The undead form up into ranks and growl a war chant!" << endl;
cout << commander <<" shouts, CHARGE!!!" << endl;
cout << endl;
cout << "Warriors from both sides blitz across the field!" << endl;
cout << endl;
cout << "*The Carnage has begun!*" << endl;
cout << "*Steal, Sparks, and Flesh flies" << endl;
}
void battleOutcome()
{
int zombieLives = numberOfZombies;
int humanLives = numberOfHumans;
int randomNumber = 0;
int humanDeath = 0;
int zombieDeath = 0;
double newHumanLife = 0;
double newZombieLife = 0;
Zombies zombieBattleData;
Humans humanBattleData;
srand(time(NULL));
zombieBattleData.setAttackPower(20.0);
humanBattleData.setAttackPower(35.0);
zombieBattleData.setDefensePower(15.0);
humanBattleData.setDefensePower(20.0);
zombieBattleData.setHealthPoints(150.0);
humanBattleData.setHealthPoints(300.0);
while(zombieLives && humanLives > 0)
{
randomNumber = 1+(rand()%10);
if(randomNumber < 6)
{
newHumanLife = humanBattleData.healthPoints - zombieBattleData.attackPower;
if(newHumanLife <= 0)
{
humanLives--;
humanDeath++;
}
}else
{
newZombieLife = zombieBattleData.healthPoints - humanBattleData.attackPower;
if(newZombieLife <= 0)
{
zombieLives--;
zombieDeath++;
}
}
}
if(zombieLives <= 0)
{
cout << "Humans have emerged victorious!" << endl;
cout << "Human Deaths: " << humanDeath << "Zombie Deaths: " << zombieDeath << endl;
}else if(humanLives <= 0)
{
cout << "Zombies have emerges victorious!" << endl;
cout << "Human Deaths: " << humanDeath << "Zombie Deaths: " << zombieDeath << endl;
}
I know the code wont run properly as of now. What I was doing was a test run to make sure I was receiving no errors. The two errors I'm getting are:
armySimulatorMain.cpp:25:10: error: 'double ArmyValues::healthPoints' is protected
armySimulatorMain.cpp:115:67: error: within this context.
newHumanLife = humanBattleData.healthPoints - zombieBattleData.attackPower;
This is the case for Attack Power and Health Power however, Defense power is clearing the errors. i don't understand why they are getting flagged. I'm changing the variable through the public function so shouldn't this be allowed?
Also, I'm calling three variables outside of all functions because they are being used by multiple functions. How can I plug those variables somewhere I don't like that they are floating freely above everything?
Thanks guys I can't believe I forgot about getters... Anyway the code runs now much appreciated I'll make sure to remember this time xD
It's not complaining about the line where you set the values; as you say, that uses a public function. But here, you try to read the protected member variables:
newHumanLife = humanBattleData.healthPoints - zombieBattleData.attackPower;
You only try to read two variables, and those are the ones it complains about.
You'll need a public getter function to read the values.
You need to do something like:
public:
double gethealthPoints()
{
return healthPoints;
}
because attackPower, defensePower, healthPoints are all protected, so if you want to access to any of them you need a getter, otherwise you will always receive an protect error

Trying to make string array passed through methods C++

I'm trying to read names and ages from user, until user inputs "stop". Then just print all these values. Please help me , I'm just the beginner in C++
// Pass.cpp
// Reading names and ages from user and outputting them
#include <iostream>
#include <iomanip>
#include <cstring>
using std::cout;
using std::cin;
using std::endl;
using std::setw;
using std::strcmp;
char** larger(char** arr);
int* larger(int* arr);
void read_data(char*** names, int** ages);
void print_data(char*** names, int** ages);
int main()
{
char** names = new char*[5];
char*** p_names = &names;
int* ages = new int[5];
int** p_ages = &ages;
read_data(p_names,p_ages);
print_data(p_names,p_ages);
}
void read_data(char*** names, int** ages)
{
const char* sent = "stop";
const int MAX = 15;
int count = 0;
char UI[MAX];
cout << "Enter names and ages."
<< endl << "Maximum length of name is " << MAX
<< endl << "When stop enter \"" << sent << "\".";
while (true)
{
cout << endl << "Name: ";
cin.getline(UI,MAX,'\n');
if (!strcmp(UI, sent))
break;
if (count + 1 > sizeof (&ages) / sizeof (&ages[0]))
{
*names = larger(*names);
*ages = larger(*ages);
}
*names[count] = UI;
cout << endl << "Age: ";
cin >> *ages[count++];
}
}
void print_data(char*** names, int** ages)
{
for (int i = 0; i < sizeof(*ages) / sizeof(*ages[0]);i++)
{
cout << endl << setw(10) << "Name: " << *names[i]
<< setw(10) << "Age: " << *ages[i];
}
}
char** larger(char** names)
{
const int size = sizeof(names) / sizeof(*names);
char** new_arr = new char*[2*size];
for (int i = 0; i < size; i++)
new_arr[i] = names[i];
return new_arr;
}
int* larger(int* ages)
{
const int size = sizeof(ages) / sizeof(*ages);
int* new_arr = new int[2 * size];
for (int i = 0; i < size; i++)
new_arr[i] = ages[i];
return new_arr;
}
You are really over complicating things.
Given the original problem:
Write a program that reads a number (an integer) and a name (less than
15 characters) from the keyboard. Design the program so that the data
is done in one function, and the output in another. Store the data in
the main() function. The program should end when zero is entered for
the number. Think about how you are going to pass the data between
functions
The problem wants you to think about passing parameters to functions. A simple solution would be:
#include "stdafx.h"
#include <iostream>
#include <iomanip>
using namespace std;
// Pass in a char array and an integer reference.
// These values will be modified in the function
void read_data(char name[], int& age)
{
cout << endl << "Age: ";
cin >> age;
cin.ignore();
cout << endl << "Name: ";
cin.getline(name, 16);
}
// Pass a const array and an int value
// These values will not be modified
void print_data(char const *name, int age)
{
cout << endl << setw(10) << "Name: " << name
<< setw(10) << "Age: " << age;
}
int main()
{
char name[16];
int age;
cout << "Enter names and ages."
<< endl << "Enter 0 age to quit.";
do {
read_data(name, age);
print_data(name, age);
} while (0 != age)
}
EDIT: Modified per user3290289's comment
EDIT2: Storing data in an array
// Simplify by storing data in a struct (so we don't have to manage 2 arrays)
struct Person {
char name[16];
int age;
};
// Returns how many People were input
int read_data(Person*& arr)
{
int block = 10; // How many persons to allocate at a time
arr = NULL;
int arr_size = 0;
int index = 0;
while (true) {
if (index == arr_size) {
arr_size += block;
arr = (Person *)realloc(arr, arr_size * sizeof(Person)); // Reallocation
// Should check for error here!
}
cout << endl << "Age: ";
cin >> arr[index].age;
cin.ignore();
if (0 == arr[index].age) {
return index;
}
cout << endl << "Name: ";
cin.getline(arr[index++].name, 16);
}
}
void print_data(Person *arr, int count)
{
for (int i = 0; i < count; i++) {
cout << endl << setw(10) << "Name: " << arr[i].name
<< setw(10) << "Age: " << arr[i].age;
}
}
int main()
{
Person *arr;
int count = read_data(arr);
print_data(arr, count);
free(arr); // Free the memory
}
try this:
#include <iostream>
#include <iomanip>
#include <vector>
#include <sstream>
using std::cout;
using std::cin;
using std::endl;
using std::setw;
using std::strcmp;
void read_data(std::vector<std::string> &names, std::vector<int> &ages);
void print_data(std::vector<std::string> &names, std::vector<int> &ages);
int main()
{
std::vector<std::string> names;
std::vector<int> ages;
read_data(names, ages);
print_data(names, ages);
}
void read_data(std::vector<std::string> &names, std::vector<int> &ages)
{
const char* sent = "stop";
cout << "Enter names and ages."
<< endl << "When stop enter \"" << sent << "\".";
while (true)
{
std::string input;
cout << endl << "Name: ";
std::getline(cin, input);
if (!strcmp(input.c_str(), sent))
break;
names.push_back(input);
cout << endl << "Age: ";
std::string age;
std::getline(cin, age);
ages.push_back(atoi(age.c_str()));
}
}
void print_data(std::vector<std::string> &names, std::vector<int> &ages)
{
for (int i = 0; i < names.capacity() ; i++)
{
cout << endl << setw(10) << "Name: " << names.at(i)
<< setw(10) << "Age: " << ages.at(i);
}
}
One problem I see is this if statement:
if (count + 1 > sizeof (&ages) / sizeof (&ages[0]))
&ages is the address of an int**, a pointer, and so it's size is 8 (usually) as that is the size of a pointer type. The function does not know the size of the array, sizeof will only return the correct answer when ages is declared in the same scope.
sizeof(&ages) / sizeof(&ages[0])
will always return 1
I believe one natural solution about this problem is as follows:
create a "std::map" instance. Here std::map would sort the elements according to the age. Here my assumption is after storing the data into the container, you would like to find about a particular student age/smallest/largest and all various manipulation with data.Just storing and printing the data does not make much sense in general.
create a "std::pair" and take the both input from the user into the std::pair "first" and "second" member respectively. Now you can insert this "std::pair" instance value into the above "std::map" object.
While printing, you can now fetch the each element of "std::map" in the form of "std::pair" and then you can display pair "first" and "second" part respectively.