error C2064

[ftball22]

I am testing out a simple template, but every time i try it, this error C2064 : term does not evaluate to a function taking 0 arguments, pops up. Seen as i am very new to C++, it will probabily be something stupid, but if i don't ask i'll never find out.

#include <iostream>;
#include <cstdlib>;

using namespace std;

int main()
{
 int input;
   
  cout<<"1. Play game\n";
  cout<<"2. Load game\n";
  cout<<"3. Play multiplayer\n";
  cout<<"4. Exit\n";
  cout<<"Selection: ";
  cin>> input;
  switch ( input ) {
  case 1:            
    playgame();
    break;
  case 2:           
   loadgame();
    break;
  case 3:           
    playmultiplayer();
    break;
  case 4:           
    cout<<"Thank you for playing!\n";
    break;
  default:          
    cout<<"Error, bad input, quitting\n";
    break;
  }
  cin.get();
}

Thanks for help in advance.

[Elysia]

Which line?
Is it one of the

playgame();
loadgame();
playmultiplayer();

?

[ftball22]

Sorry should have mentioned that. Unfortunately it's all three.

[Elysia]

Then it's because you haven't defined those functions. You cannot call a function that does not exist, can you?
Also,

#include <iostream>;
#include <cstdlib>;

should be

#include <iostream>
#include <cstdlib>

[ftball22]

Then it's because you haven't defined those functions

Sorry like i said i'm new, how do you mean?

[anon]

Those functions have to be declared before you use them.

void playgame();
//etc

And then they need to be implemented somewhere

void playgame()
{
    //implementation
}

[Elysia]

Sorry like i said i'm new, how do you mean?

Essentially, you haven't created the functions. They don't exist.

[Michael432000]

I saw from your previous thread that you were struggling with functions.

Here, the function menu() uses the return statement to return choice: Notice the function is declared above main() and implemented below.

#include <cstdlib>
#include <iostream>
using namespace std;

int menu();

int main(){
    int choice = menu();
    cout << "You chose option " << choice << endl;
    
    system ("pause"); // temp to stop console closing
    return 0;
}

int menu(){
    int choice;

    cout << " **** Menu ****" << endl << endl;
    cout << "(1) Option 1." << endl;
    cout << "(2) Option 2." << endl;
    cout << "(3) Option 3." << endl;
    cout << "(4) Redisplay menu." << endl;
    cout << "(5) Quit." << endl << endl;

    cout << ": ";
    cin >> choice;
    return choice;
}

In your select statement, there is no value to be returned, so in this case you would use a void type for the function and declare and implement it as anon has pointed out above.

To be honest, as a beginner myself, I’m not sure why this is referred to as a function.

[novacain]

The way I understand it is.....

The compiler 'reads' from the top of the code down.

It has to have already 'read' what a function does before you can use the function (well, at least the function name, input and output).

If you declare a function twice, the first one is over-written by the second one. So you can just declare an empty 'prototype' for the function and fill the details in later in the code.

You could also just write the functions in a different order (but this gets impossible to do in big programs).

#include <cstdlib>
#include <iostream>
using namespace std;

//we need to use menu() in main() so it must appear before main() 
int menu()
{
    int choice;

    cout << " **** Menu ****" << endl << endl;
    cout << "(1) Option 1." << endl;
    cout << "(2) Option 2." << endl;
    cout << "(3) Option 3." << endl;
    cout << "(4) Redisplay menu." << endl;
    cout << "(5) Quit." << endl << endl;

    cout << ": ";
    cin >> choice;
    return choice;
}

int main()
{
    int choice = menu();
    cout << "You chose option " << choice << endl;
    
    system ("pause"); // temp to stop console closing
    return 0;
}

[Elysia]

The compiler will parse a file top to bottom. To use something, or call a function, we must first make the compiler aware of that identifier, such as a type or a function.
This is done by declaring an identifier. This basically introduces the identifier to the compiler. The compiler now knows this identifier exists, but it has as of yet no idea what it is, or what it contains. Under certain circumstances, this is fine. For functions, for example, it is fine.
Then comes the "definition" part, which formally introduces this identifier to the compiler. The definition will tell the compiler exactly what this identifier is.
Lastly comes the implementation. This is basically the code inside a function. It is not necessary to be associated with an identifier. The compiler can generate code to call a function without knowing what it contains or does. But you do, of course, have to tell the compiler at some point what the function contains. How else can it generate the appropriate code for the program?

Examples of declarations are function prototypes. They are enough for a compiler to call a function.
An example of a definition is a struct or class. You can just type "class myclass;", but when you use the class, the compiler must know what this type is. So the whole information about the contents of the class is the definition. And finally, the code inside any of the class's functions are the implementation.

Sometimes, declarations, definitions and implementations can be combined. Examples are when you're creating your struct. You don't have to type "struct mystruct;" first. Another example is a function, like menu above. It is a declaration and an implementation. When you create a variable, you are declaring and defining it.