[SOLVED]

[jtst1]

It seems that Microsoft hates me lol. Basically it's giving me an error saying "cout and cin are undeclared" when i put #include <iostream> and using namespace std;. here's my code:

Code: Select all

#include <iostream>
using namespace std
int Area(int length, int width);
int main()
{
int lengthOfYard;
int widthOfYard;
int areaOfYard;
cout << "\nHow wide is your yard?";
cin >> widthOfYard;
cout << "\nHow long is your yard?";
cin >> lengthOfYard;
areaOfYard = Area(lengthOfYard, widthOfYard);
cout << "\nYour yard is "; << areaOfYard << "in square feet\n\n";
	return 0;
}

int Area(int yardLength, int yardWidth)
{
	return yardLength * yardWidth;
}

one more thing, why is it that vc++ tells me to put #include <stdafx.h> but that doesnt resolve it

[andrew]

Code: Select all

using namespace std

should be:

Code: Select all

using namespace std;

If you make your code neater it will be much easier to spot things like this.

EDIT:

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#include <iostream>

using namespace std;

int Area(int, int);

int main()
{
    int lengthOfYard;
    int widthOfYard;
    int areaOfYard;

    cout << "\nHow wide is your yard?";
    cin >> widthOfYard;

    cout << "\nHow long is your yard?";
    cin >> lengthOfYard;

    areaOfYard = Area(lengthOfYard, widthOfYard);
    cout << "\nYour yard is "; << areaOfYard << "in square feet\n\n";

    return 0;
}

int Area(int yardLength, int yardWidth)
{
   return yardLength * yardWidth;
}

There is still an error, see if you can spot it.

[hurstshifter]

I see the errrrrrooorrrr......

[jtst1]

Code: Select all

using namespace std

should be:

Code: Select all

using namespace std;

If you make your code neater it will be much easier to spot things like this.

EDIT:

Code: Select all

#include <iostream>

using namespace std;

int Area(int, int);

int main()
{
    int lengthOfYard;
    int widthOfYard;
    int areaOfYard;

    cout << "\nHow wide is your yard?";
    cin >> widthOfYard;

    cout << "\nHow long is your yard?";
    cin >> lengthOfYard;

    areaOfYard = Area(lengthOfYard, widthOfYard);
    cout << "\nYour yard is "; << areaOfYard << "in square feet\n\n";

    return 0;
}

int Area(int yardLength, int yardWidth)
{
   return yardLength * yardWidth;
}

There is still an error, see if you can spot it.

Was the error the extra ";"

Code: Select all

   cout << "\nYour yard is "; << areaOfYard << "in square feet\n\n";

Edit-------
well i read the note about stdafx.h, and i just went into the header and added #include <iostream> and using namespace std; Worked perfectly. I have to put any other header requirements into stdafx...weird eh?

[andrew]

Was the error the extra ";"

That's it.

Edit-------
well i read the note about stdafx.h, and i just went into the header and added #include <iostream> and using namespace std; Worked perfectly. I have to put any other header requirements into stdafx...weird eh?

You shouldn't need stdafx.h for this code.

[jtst1]

Was the error the extra ";"

That's it.

Edit-------
well i read the note about stdafx.h, and i just went into the header and added #include <iostream> and using namespace std; Worked perfectly. I have to put any other header requirements into stdafx...weird eh?

You shouldn't need stdafx.h for this code.

I know, it's weird but everytime i take it out and put #include <iostream> and using namespace std; it gives me an error.
O well atleast I can get back to learning!! :P

[JaxDragon]

A c++ book I have says that you NEED stdafx.h in every visual studio application. I never had to, but I guess it's true for some people.

[MarauderIIC]

If you turn off precompiled headers in your compilation options, you don't need it.

[jtst1]

If you turn off precompiled headers in your compilation options, you don't need it.

Ahh thank you Marauder.
I figured I might as well post this in this post as not to make another.
In my book it was talking about Recursion, and using the Fibonacci series, now i get the whole 1 1 2 3 5 8 13 21 thing, but I don't understand the code, and the book did a shitty job or explaining it. here's the code if anyone wants to look at it.

Code: Select all

#include "stdafx.h"

int fib (int n);

	int main()
	{
		int n, answer;

		cout << "Enter number to find: ";
		cin >> n;

		cout << "\n\n";
		answer = fib(n);

		cout << answer << " Is the " << n << "th Fibonacci number\n";
		Sleep(50000); // I added the sleep
		return 0;
	}

			int fib (int n)
		{
			cout << "Processing fib)" << n << ")...";
			if (n < 3)
			{
				cout << "Return 1!\n";
				return (1);
			}
			else
			{
				cout << "Call fib(" << n-2 << ") and fib(" << n-1 << ").\n";
				return( fib(n-2) + fib(n-1));
			}
		}

[short]

What exactly would you liked explained about the series?

[jtst1]

I would like to understand what the code does, like the n-2+n-1 I don't understand what n is, and F

[short]

First off, I made a few code changes so that it would compile with my compiler, as well as I commented on a few coding changes I made.

Code: Select all

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

int fib (int n);

int main()
{
	int n, answer;

	cout << "Enter number to find: ";
	cin >> n;

	cout << "\n\n";
	answer = fib(n);

	cout << answer << " Is the " << n << "th Fibonacci number\n";
	//Sleep(50000); // I added the sleep
	cin >> answer; // I changed this because calling sleep is an awful habit to get into. It is very cpu intensive,
	// calling cin just waits for an input thats not null then exits in this case.
	return 0;
   }

int fib(int n)
{
	cout << "Processing fib)" << n << ")...";
	if (n < 3)
	{
		cout << "Return 1!\n";
		return(1);
	}
	else
	{
		cout << "Call fib(" << n-2 << ") and fib(" << n-1 << ").\n";
		return( fib(n-2) + fib(n-1));
	}
}

Note: I'm awful at explaining things.

The fib(int n) function calls itself in the return statement You can see that

Code: Select all

 return (fib(n-2) + fib(n-1))

The Fibonacci series is found using recursion.
Mathematically it can be shown as . You can see that the series is defined using Fib(n-1) + Fib(n-2), the same as your return statement.

When your return statement is called, it calls fib using n-1, without actually ever finishing the return statement. Instead it goes on to call fib(n-1), creating a sort of back order or stack of functions that have been called. These are stored on the computers stack, which you will learn about later on. It keeps on doing this until eventually the base case is reached (n < 3). Every time it calls fib(n-1) it creates a stack of function calls. You know each function is never finished until the base case is reached. One the base case is reached, fib finally returns a value of 1. Once this happens, it has a "stack" of fib calls to return through, finally able to close all those open function calls until it gets back to the very first fib(n) call where it returns a value to answer which is then printed to the screen. As you can see on every return call it calls fib twice. I don't exactly remember how it handles both calls, of whether or not it handles the fib(n-2) after all the fib(f-1) have returned or not.

If someone knows feel free to remind me.

Also, I realize my explanation may be confusing, It's a hard concept to grasp, but even harder to explain (for me personally). I suggest you do some looking up on recursion, and if you really want an understanding take a look at induction. It's a way to prove things mathematically. Hopefully someone will come along and can explain it a little bit better then I can. Let me know if anything doesn't make sense and I will try.

[jtst1]

First off, I made a few code changes so that it would compile with my compiler, as well as I commented on a few coding changes I made.

Code: Select all

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

int fib (int n);

int main()
{
	int n, answer;

	cout << "Enter number to find: ";
	cin >> n;

	cout << "\n\n";
	answer = fib(n);

	cout << answer << " Is the " << n << "th Fibonacci number\n";
	//Sleep(50000); // I added the sleep
	cin >> answer; // I changed this because calling sleep is an awful habit to get into. It is very cpu intensive,
	// calling cin just waits for an input thats not null then exits in this case.
	return 0;
   }

int fib(int n)
{
	cout << "Processing fib)" << n << ")...";
	if (n < 3)
	{
		cout << "Return 1!\n";
		return(1);
	}
	else
	{
		cout << "Call fib(" << n-2 << ") and fib(" << n-1 << ").\n";
		return( fib(n-2) + fib(n-1));
	}
}

Note: I'm awful at explaining things.

The fib(int n) function calls itself in the return statement You can see that

Code: Select all

 return (fib(n-2) + fib(n-1))

The Fibonacci series is found using recursion.
Mathematically it can be shown as . You can see that the series is defined using Fib(n-1) + Fib(n-2), the same as your return statement.

When your return statement is called, it calls fib using n-1, without actually ever finishing the return statement. Instead it goes on to call fib(n-1), creating a sort of back order or stack of functions that have been called. These are stored on the computers stack, which you will learn about later on. It keeps on doing this until eventually the base case is reached (n < 3). Every time it calls fib(n-1) it creates a stack of function calls. You know each function is never finished until the base case is reached. One the base case is reached, fib finally returns a value of 1. Once this happens, it has a "stack" of fib calls to return through, finally able to close all those open function calls until it gets back to the very first fib(n) call where it returns a value to answer which is then printed to the screen. As you can see on every return call it calls fib twice. I don't exactly remember how it handles both calls, of whether or not it handles the fib(n-2) after all the fib(f-1) have returned or not.

If someone knows feel free to remind me.

Also, I realize my explanation may be confusing, It's a hard concept to grasp, but even harder to explain (for me personally). I suggest you do some looking up on recursion, and if you really want an understanding take a look at induction. It's a way to prove things mathematically. Hopefully someone will come along and can explain it a little bit better then I can. Let me know if anything doesn't make sense and I will try.

I sort of understand what you are saying, and as you said it's a hard thing to grasp. Honestly i'm not understanding how it gets that "blank" is the n'th number in the fib series. But you did help me sort of understand it, so Thank you. I'll go look up recursion and induction.

[short]

blank?

[jtst1]

The blank was for a number any number. How does it know that 8 is the 6th number in the fib series? or 10 is some other number in the series.