Programming error in C++ - c++

I recently started learning C++ but I came across a problem. The program given below is not giving me the desired result as I only see 'Hi' in the result but not what's written in the void function. Please tell me the reason that this is happening along with the solution.
I am using Xcode 6.3.1 and the I have selected the language C++.
#include <iostream>
using namespace std;
void ABC () {
cout << "Hey there ! \n";
}
int main () {
cout << "Hi \n";
void ABC ();
return 0;
}

You are redeclaring a void ABC() function inside main(). Just call ABC(); without the void.
You can take a look at this question about declaring a function within the scope of another.

In your code your function call was wrong.
When you call your function you don't need to add the return type:
#include
void ABC () {
cout << "Hey there ! \n";
}
int main () {
cout << "Hi \n";
ABC ();
return 0;
}

you need to call your method and not declare it inside main
#include <iostream>
using namespace std;
void ABC () {
cout << "Hey there ! \n";
}
int main ()
{
cout << "Hi \n";
ABC ();
return 0;
}
EDIT 1:
Since you started learning C++ i recommend the following recommendations to make sure your code is cleaner. Please note , these are not rules by any mean , but more of best practices and a style of coding.
Use meaningful names for your variables, methods, functions , classes
... So instead of ABC() name it something that if you (or someone
else is reading it) will now what it suppose to do.
When calling methods and functions try to declare them with the
appropriate returning value. Void by definition doesn't return any
value it just process the code inside of it. so your methods/function
should return appropriate values of do what it suppose to.
Here's version 2 of your code with examples of 3 different methods and calls:
#include <iostream>
using namespace std;
int sum;
string MethodReturningString()
{
return "Hey there i am the result of a method call !";
}
int MethodReturningInt()
{
return 5;
}
void CalculateSum(int x,int y)
{
sum=x+y;
}
int main()
{
cout << MethodReturningString() << endl;
cout << MethodReturningInt() << endl;
cout << "Calculating sum:" ;
CalculateSum(5,4);
cout << sum << endl;
return 0;
}
Happy coding

In C++, like pretty much any other language, you do not specify the return type when calling a function. So change the line that reads:
void ABC ();
to:
ABC();

Try this:
#include <iostream>
using namespace std;
void ABC () {
cout << "Hey there ! \n";
}
int main () {
cout << "Hi \n";
ABC();
return 0;
}
You should call a function simply by stating its name and adding parentheses.

instead of using void ABC() for calling the function ABC() in main(), use the following code:
#include
void ABC ()
{
cout << "Hey there ! \n";
}
int main ()
{
cout << "Hi \n";
ABC ();
return 0;
}

Related

C++ endl not printing new line when called from a method

New to C++
My understanding is endl will add a new line. So with the following piece of code:
#include <iostream>
using namespace std;
void printf(string message);
int main()
{
cout << "Hello" << endl;
cout << "World" << endl;
printf("Hello");
printf("World");
return 0;
}
void printf(string message) {
cout << message << endl;
}
I expect the output to be:
Hello
World
Hello
World
But, strangely, the output is:
Hello
World
HelloWorld
Looks like, when called from the user-defined method, endl is not adding new line..??
What is wrong with my understanding here. Please advise.
The problem is that due to overload resolution the built in printf function is selected over your custom defined printf function. This is because the string literal "Hello" and "World" decays to const char* due to type decay and the built in printf function is a better match than your custom defined printf.
To solve this, replace the printf calls with :
printf(std::string("Hello"));
printf(std::string("World"));
In the above statements, we're explicitly using std::string's constructor to create std::string objects from the string literal "Hello" and "World" and then passing those std::string objects by value to your printf function.
Another alternative is to put your custom printf inside a custom namespace. Or you can name your function other than printf itself.
It's using the inbuilt printf method.
Try to explicitly use std::string so that it'll call custom printf method.
printf(std::string("Hello"));
printf(std::string("World"));
Or you can put your method in a different namespace:
#include <iostream>
namespace test
{
extern void printf(const std::string& message);
}
int main()
{
std::cout << "Hello" << std::endl;
std::cout << "World" << std::endl;
test::printf("Hello");
test::printf("World");
return 0;
}
void test::printf(const std::string& message) {
std::cout << message << std::endl;
}
try renaming the "printf" function to "print" it works fine-
#include <iostream>
using namespace std;
void print(string message);
int main()
{
cout << "Hello" << endl;
cout << "World" << endl;
print("Hello");
print("World");
cout <<endl;
return 0;
}
void print(std::string message) {
cout << message << endl;
}
You should pick function name other than printf(); like Print().

C++ How to implement this code into the heap properly

I am working on a class assignment to create three classes nested inside each other. I need to make constructors and deconstructors for each that have a message that goes along with them. Finally, I need to create an instance of each class using new and call the display() function to show their message, followed by delete.
I have completed the assignment but in the wrong way, and I am confused about how I can properly put the code into the heap instead of the stack (as I was advised by my course tutor).
This is what I started with: (this code seems to work well, but does not fulfill the assigned project)
#include <string>
#include <iostream>
#include <fstream>
using namespace std;
class Hen {
public:
Hen();
~Hen();
string display(void) {
return ("Im a Hen");
}
class Nest;
friend Nest;
class Nest {
public:
Nest();
~Nest();
string display(void) {
return ("Im a Nest");
}
class Egg;
friend Egg;
class Egg {
public:
Egg();
~Egg();
string display(void) {
return ("Im an egg");
}
};
};
};
Hen::Hen() {
cout << "I construct Hens" << endl;
}
Hen::~Hen() {
cout << "I deconstruct Hens" << endl;
}
Hen::Nest::Nest() {
cout << "I construct Nests" << endl;
}
Hen::Nest::~Nest() {
cout << "I deconstruct Nests" << endl;
}
Hen::Nest::Egg::Egg() {
cout << "I construct Eggs" << endl;
}
Hen::Nest::Egg::~Egg() {
cout << "I deconstruct Eggs" << endl;
}
int main() {
Hen hone;
Hen::Nest none;
Hen::Nest::Egg eone;
string h, n, e;
h = hone.display();
n = none.display();
e = eone.display();
cout << h << "\n" << n << "\n" << e << endl;
}
Where I am stuck is when I try to implement my code inside the heap, it seems to break by the second class:
#include <string>
#include <iostream>
#include <fstream>
using namespace std;
class Hen {
public:
void display() {
cout << "Im a Hen" << endl;
}
class Nest;
friend Nest;
class Nest {
public:
void display() {
cout << "Im a Nest" << endl;
}
class Egg;
friend Egg;
class Egg {
public:
void display() {
cout << "Im an egg" << endl;
}
};
};
};
int main() {
Hen *hone = new Hen();
Hen::Nest *none = new Nest();
hone -> display();
none -> display();
}
Question 1:
If I remove all the information related to nest, the program runs Hen just fine and returns the "I'm a hen" statement. But, when I add in nest, the warning I recieve is
"error: expeected type-specifier before 'Nest'
Hen::Nest *none = new Nest();"
I do not understand what I am doing wrong as I did the exact same process for Hen and it worked. I do know that the error must be in the way Nest gets called through hen?
I apologize if this question is obvious, but I am just starting c++ and do not understand why I am getting these messages...
Thanks for your help!

How do I get my constructor and functions to work so my main() is able to display both the string and int data?

I am learning about functions and classes, and wrote my own code. I used the constructor to just initialize the variables. I have a function that is supposed to get the info I initialized with the constructor and allow me to display it. However, it doesn't want to work. I am not really sure what I am doing wrong. My error code says that I have unresolved externals because of my "void" function. I thought my function was not returning anything but rather just displaying the input it got from the initialization of the constructor.
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
class Berries {
string Nameofberries;
int Price;
public:
Berries (string N,int B)
{
Nameofberries = N;
Price = B;
}
void GetBerryInfo(const Berries& B)
{
cout << B.Nameofberries << endl;
cout << B.Price << endl;
}
};
void GetBerryInfo (const Berries& B);
int main ()
{
Berries Berryinfo1( "Raspberries", 7);
cout << GetBerryInfo;
system("pause");
return 0;
}
There are several mistakes.
void GetBerryInfo(const Berries& B)
{
cout << B.Nameofberries << endl;
cout << B.Price << endl;
}
should be
void GetBerryInfo()
{
cout << Nameofberries << endl;
cout << Price << endl;
}
==================================================================
void GetBerryInfo (const Berries& B);
should be removed.
==================================================================
cout << GetBerryInfo;
should be
Berryinfo1.GetBerryInfo();
==================================================================
All computer langauges are fussy, you have to get the details right, as well as understand the concepts.
This will do what you wanted:
# include <iostream>
# include <iomanip>
# include <string>
using namespace std;
class Berries {
string Nameofberries;
int Price;
public:
Berries (string N,int B)
{
Nameofberries = N;
Price = B;
}
void GetBerryInfo()
{
cout << Nameofberries << endl;
cout << Price << endl;
}
};
int main ()
{
Berries Berryinfo1( "Raspberries", 7);
Berryinfo1.GetBerryInfo();
system("pause");
return 0;
}
A couple of points on your mistakes:
GetBerryInfo() was declared inside the class. You don't need to re-declare it in the global scope. That 2nd declaration should be removed.
To be invoked, functions (like GetBerryInfo) must have () at the end of them like so: GetBerryInfo().
There is no point for GetBerryInfo() to take Berries as a paremeter. It is a member function that is part of the class Berries. It has access to all data members of a Berries instance already.
You don't need to use cout here: cout << GetBerryInfo; because the function body already sends the data members to cout. This function returns void so it doesn't make sense to send this to cout anyway.

no match for operator '<<' Can someone aid with void function error? [c++]

This post treats the same error, but the poster isn't have trouble with a void function.
This post concerns the "void" type of function, but the poster is advised to change the function type to "string", which does not help my case.
My code executes fine, except for a literal "0" at the end of the output. When I change the function type to "void", I am met with the above error.
I have been through the tutorial on this numerous times, and have searched thoroughly, yet have been unable to resolve this issue.
//my code
#include <iostream>
using namespace std;
int intervalcountdown (int a, int b) {
for(a; a>0; a = a - b) {
cout << a;
if(a<=b) {
break;
}
cout << ",";
}
cout << ".";
return 0;
}
int main () {
cout << intervalcountdown(20,3);
return 0;
}
Just don't print what you don't want.
#include <iostream>
using namespace std;
void intervalcountdown (int a, int b) { // change return type to void
for(; a>0; a = a - b) { // meaningless a is removed
cout << a;
if(a<=b) {
break;
}
cout << ",";
}
cout << ".";
// remove the return statement because the return type is now void
}
int main () {
intervalcountdown(20,3); // remove extra printing
return 0;
}

Can someone explain why only one of my functions prints to console?

Here is my code in C++:
#include <iostream>
using namespace std;
int tuna = 20; // this is global
//main function
int main()
{
int tuna = 69; // this is local
cout << tuna << endl;
}
//fish function
int fish()
{
cout << tuna << endl; // this should print global?
}
The fish function doesn't print to the console when I run it. I am not sure why and it doesn't make sense to me.
You are not calling fish() so it doesn't seem strange its body is is not executed.
Try with:
int main()
{
fish();
return 0;
}
because main() is the only possible entry point for your program and the only way to call other, user-defined, functions.
Do you ever call the function (fish) ? Not in your sample.
Because you don't call it at all.