C++...wtf?

EXreaction · January 17th, 2006, 04:24 PM

I have been making a BlackJack program with C++...and I am really stumped on this part...

For some reason, I noticed that the totals for how many times you have won were getting screwed up...starting at -1 instead of 0...so, I went through, and I found this part to be the problem:

Code:

	for (int g=1; g<6; g++)
	{
		youCard[g]=-1;
		compCard[g]=-1;
	}

That is the part that is screwing everything up...and just to show you, if you run this:

Code:

#include<iostream.h>

int youWin=0, compWin=0, bothLose=0, tie=0, numHands=0;

int youCard[5], compCard[5];

int main()
{
	cout<<endl<<endl<<"You have won "<<youWin<<" times."<<endl;
	cout<<"The computer has won "<<compWin<<" times."<<endl;
	cout<<"Both of you have lost "<<bothLose<<" times."<<endl;
	cout<<"You have tied "<<tie<<" times."<<endl;

	for (int g=1; g<6; g++)
	{
		youCard[g]=-1;
		compCard[g]=-1;
	}

	cout<<endl<<endl<<"You have won "<<youWin<<" times."<<endl;
	cout<<"The computer has won "<<compWin<<" times."<<endl;
	cout<<"Both of you have lost "<<bothLose<<" times."<<endl;
	cout<<"You have tied "<<tie<<" times."<<endl;

	return(0);
}

It outputs this in the console:

Quote:

You have won 0 times.
The computer has won 0 times.
Both of you have lost 0 times.
You have tied 0 times.

You have won -1 times.
The computer has won 0 times.
Both of you have lost 0 times.
You have tied 0 times.
Press any key to continue

If you play with it, and try:

Code:

for (int g=1; g<5; g++)

instead of:

Code:

for (int g=1; g<6; g++)

It doesn't screw up the totals...but I need to set all the numbers in the arrays to -1...otherwise it gets errors in other sections...

Any ideas?

I can set the arrays to have 6 numbers in them...and it will work in the program(since I only use the first 5)...but wtf is going on?

oliver w · January 18th, 2006, 06:13 PM

um... im guessing you're meant to get all answers showing 0? and mustn't have any -1's?
i got all zeros and i tried some other numbers and they ended up the same...
maybe try a different compiler (i got dev-c++) or something in the other part of the program is stuffing it up :S

Peter M · January 18th, 2006, 06:56 PM

That's because C and C++ have array indices starting with 0.

You want to say

for (i=0; i<N; i++) {

there (N being the length of the array, 6 in your case).

Know your pointer arithmetics: stuff[n] is equal to *(stuff+n). Your loop is overrunning the end of the array, and screws up other data - which happens to be one of your totals.

Oh, and DON'T declare variables mid-code. That'll get you an F--- in coding style.

EXreaction · January 18th, 2006, 07:19 PM

Quote:

Originally Posted by Peter M

That's because C and C++ have array indices starting with 0.

You want to say

for (i=0; i<N; i++) {

there (N being the length of the array, 6 in your case).

Know your pointer arithmetics: stuff[n] is equal to *(stuff+n). Your loop is overrunning the end of the array, and screws up other data - which happens to be one of your totals.

Oh, and DON'T declare variables mid-code. That'll get you an F--- in coding style.

Oh, I get it now...so it is really 0-4 for an array of 5! xD Makes sense now.

You mean declaring them in the loop? Whats so bad about that? I am only using it for the loop...

Peter M · January 19th, 2006, 09:05 AM

Don't obfuscate -

for (int i = 0, ...

does exactly that. Say

int i;

...

for ( i= ...

Also, pull your data into main(). Global variables are badbadbad as well. That'll get you less than an F.

C++ is about making objects and keeping data encapsuled with the code that handles it. Keeping everything in globals is the exact opposite of good C++.

EXreaction · January 19th, 2006, 02:07 PM

Oh, ya, I can do that.

Well, I started coding with VB...and we always used globals...but I will work on it...

jkrohn · January 19th, 2006, 02:10 PM

Just out of curiosity, did someone actually TEACH you to use globals? Or is this something that you taught yourself.

Jkrohn

EXreaction · January 19th, 2006, 02:19 PM

I taught myself...I learned how to do it in VB...and just tried it in C++.

I like doing it...but a lot of people don't like it!

VHockey86 · January 19th, 2006, 02:20 PM

Ya, you should never need to use globals in a program like that.

If your data is only used inside a function (i.e. main()), then it shouldnt ever need a higher scope than that function. If you want to use that in other functoins, pass the value as a parameter.

Rootstonian · January 19th, 2006, 04:30 PM

You know, after programming for 10+ years, it's just a "rule" professors have to make kids use pointers and pass by reference. LOL

I want to use a global (or 50) in a program I'm writing, I'll use it dang it. Trash that heap!!!

I'm not doing this for a grade. Worry about problems down the road? Ha! I"ll be gone before I have to fix it. My legacy to all the nice 60's, 70's et al programmers that left me to fix all that Y2k crap!