C++ Tutorials - Absolute n00b spoonfeed

Here is a code that is to get a single letter from the user and print it out to the screen with two functions.


Here it is:

Code: Select all


#include "stdafx.h"
#include <iostream>
using namespace std;


void prinTLetteRGiven()
{
   cout << "The letter you typed in was " << letter << endl;
}


int main()
{
   char letter;

   cout << "Please input 1 letter: ";
   cin >> letter;
   prinTLetteRGiven();

   char end;
   cin >> end;
   return 0;
}



When you figure it out. Write the new code and Say why this doesn't work.

You need to add parameters and arguments like so :

Code: Select all

#include "stdafx.h"
#include <iostream>
using namespace std;


void prinTLetteRGiven(char letter)
{
   cout << "The letter you typed in was " << letter << endl;
}


int main()
{
   char letter;

   cout << "Please input 1 letter: ";
   cin >> letter;
   prinTLetteRGiven(letter);

   char end;
   cin >> end;
   return 0;
}


The first wouldnt work, because you would be outputting a variable that wasn't declared in that scope.

That one didn't work b/c "letter" was undeclared, so the program had no way of identifying "letter" before it was inputed.

Code: Select all

#include "stdafx.h"
#include <iostream>
using namespace std;


void prinTLetteRGiven()
{
   char letter;
   cin >> letter;
   cout << "The letter you typed in was " << letter << endl;
}


int main()
{
 
   cout << "Please input 1 letter: ";
   prinTLetteRGiven();

   char end;
   cin >> end;
   return 0;
}


So it appears from asib's post that you can declare a variable inside the function's parenthesis?

Like so:

Code: Select all

void prinTLetteRGiven(char letter)

Well, you can declare parameters which are basically requirements of a function, and allow you to pass values between two scopes. Via my way, you declare your char type in main, then you hand over a "copy" of your char (the copy is called an argument), as a variable named whatever you gave your parameter name and then you use that in your function. So, whilst yours would work, you wouldn't have access the the variable later on. Alternatively, you could return that value from the function and then assign a variable to the function like so :

Code: Select all

function blah (  )
{
      char y;
      cin >> y;
     cout << y << endl;
     return y;
}

int main (  )
{
     char myChar = blah (  );

     return 0;
}


You are Right.


Great Job!!!

Interesting.

You seem confused oopalonga.

Do you have any questions?

Due to scope issues, when i code something, i tend to do nothing except a menu in the main function. I then just call other functions, and do EVERYTHING there. That way, i don't have to worry about scope, or about passing variables around

Doctor Salt wrote:Due to scope issues, when i code something, i tend to do nothing except a menu in the main function. I then just call other functions, and do EVERYTHING there. That way, i don't have to worry about scope, or about passing variables around

but in bigger programs that would get confusing , and what if you accidently use that variable in another part of your progrma/game when it might stand for something like health or lvl , or magic , then you would have a serious bug and the compiler wouldnt catch it becuase you technically did nothing wrong , so try to declare variables in functions when you need them .

correct me if im wrong Mars++ or antiRTFM

Well, i would only use those variables when i need them, making each function somewhat standalone to a degree. Of course this wouldn't work for every situation, but it might make a few a lil easier. My way, you could take a function, copy paste it into a new project, rename the fucntion name to main, then test it just like that for problems. Thats how i tested my 700 line calculator, which had a TON of problems in it first time i tested it. Though its totally up to you on how you like to code it

Both rooski and Doctor salt are both right here to a certain degree.

You want to decalare and intialize variables as close to where there needed as possible. This way it's harder for them to get mixed up in the mess.

Due to scope issues, when i code something, i tend to do nothing except a menu in the main function. I then just call other functions, and do EVERYTHING there. That way, i don't have to worry about scope, or about passing variables around

I kind of understand what your saying here. It is common for games to be passing around to different functions and avoiding main, but this in no way gets rid of the limitations of scope. If a variable is declared within a function then that variable needs to be passed through arguments in order to get into a different function. I'm not going to get into passing by value and passing by reference but either way the variable has to be within those parenthesis or they will not exist in the function that is called.

I hope that cleared it up. If not... Post away!

one last thing to say on this thread: Don't forget about classes! You could technically make global variables, immune to scope by putting those variables inside classes

Doctor Salt wrote:one last thing to say on this thread: Don't forget about classes! You could technically make global variables, immune to scope by putting those variables inside classes

Well, what do you mean? Objects (instances) of that class are also subject to the rules of scope as much as any other variable. (at least when creating them locally within a function. If you make the instance out in global space, then its just like any other global variable)

Ah.... maybe we're agreeing, and i'm just over complicating things... again...


So, to take your work as an example, you make a class, like your soldier class, or ogre class, and just make all the variables public (or not, and just do the same thing, with functions) so you should be able to use them whenever you want, and it should be the same every time you call it, too.