Thread: C++: How can I update a variable

Originally Posted by cpjust

As for this for loop:

Code:

for (int (x < 100); int (x > 0); x)

Does that even compile?

Yes it compiles perfect and works with looping, 'hit' and 'block', the only problem that I get, is if I use 'hit' it will display the stats fine, with character hp being 90 and enemy hp being 5, however if when the loop comes back to ask me again, it will reset and character hp being 90 again and enemy hp being 5 still. Similar if I use 'block' the character hp will reset to 100 then decrease by 5 showing 95, and enemy hp will reset to 10 then decrease by 2 showing 8.

So from what I can tell, its working but the variables aren't updating, I don't know how to do it. One method I read was to use

Code:

(x < 100); int (x > 0); (x++))

which works, but each time the character hp increases by 1 rather than continue to decrease.

that command

Code:

(x < 100); int (x > 0); x)

is just saying that, while character hp (x) is under 100 [the starting hp] and above 0 [or he would be dead] to continue looping.

Originally Posted by tabstop

I also don't know what you think int (x < 100) does, but that isn't it, either.
stop and go back to page 1/part 1.
you are slinging around actually mean.

I answered the first one for you, and I understand what it means, it is this loop:

Code:

[for ( variable initialization; condition; variable update ) {
  // Code to execute while the condition is true
}

So its obvious that part of that, the 3rd portion is meant for the update, but I don't know what to do. The reason why I used that, is for the 1st portion which is meant for initialization, when the character gains xp or a stat boost to hp, then it will move onto the next loop accourding to the hp.

Originally Posted by cpjust

As for this for loop:

Code:

for (int (x < 100); int (x > 0); x)

Does that even compile? What's with all the int's? Since the 3rd part of the for loop does nothing, it should be an infinite loop. Usually you change the value being compared like ++x or --x or x += 5...

It'll compile. int(x<100) is interpreted as a cast from bool to int. same for int(x>0).

Originally Posted by nekkron

So from what I can tell, its working but the variables aren't updating, I don't know how to do it. One method I read was to use

Code:

(x < 100); int (x > 0); (x++))

which works, but each time the character hp increases by 1 rather than continue to decrease.

that command

Code:

(x < 100); int (x > 0); x)

is just saying that, while character hp (x) is under 100 [the starting hp] and above 0 [or he would be dead] to continue looping.

the proper syntax for that condition is:
x<100 && x>0
The condition goes between the two semicolons in a for loop.

Code:

[for ( variable initialization; condition; variable update ) {
  // Code to execute while the condition is true
}

So its obvious that part of that, the 3rd portion is meant for the update, but I don't know what to do. The reason why I used that, is for the 1st portion which is meant for initialization, when the character gains xp or a stat boost to hp, then it will move onto the next loop accourding to the hp.

Tabstop is right, whatever source you're using to learn C++, stop. Get yourself a book.

In the meantime here's a wiki link to all C++'s operators. Learn how to use them. In this case, -=, =, and both versions of -- are possible ways to decrease x.

Congratulations, you have four identical functions. Absolutely 100% identical!

That loop you've got there would be of the infinite variety.

Would you be surprised to learn that 'answer' is the only variable in that program that ever changes value?

Originally Posted by nekkron

I've been doing C++ for about 2 hours now, so please don't confuse me much

nekkron,

You are jumping-in head first and trying to write a program before learning the language. Enthusiasm is good, but this is going to get very frustrating for you, and for anyone here trying to help you.

SLOW DOWN! work-through the tutorial and get a good beginning C++ book. Once you understand variables, functions, loops, and if-statements, you can start to write interesting programs that "do something".

Originally Posted by DougDbug

Develop your code a few lines at a time.

Someday I'm going to write an essay on this topic. It seems like a lot of instructors don't really teach how to approach a programming problem. This result in lots of frustrated beginners & students. Nobody... not even experienced programmers write the whole program before trying it out!

1- Start-out with a 'Hello World" type program. You can substitute "Hello World" with some better description of the program.

2- Add one or two lines of code at a time. Compile, test-run, and debug before adding more lines.

3- Add some extra cout statements so you can "see" what the program is doing, and confirm that it's working, before you're completely done. (You can take them out, or coment them out later.)

4- When you create a function, make an empty (do-nothing) function first. Make the function prototype, the empty function definition, and the function call. Then, test-compile. If your function needs to return a value, just make it return a constant (i.e. return 10; ). It's also helpful to put a cout statement in your do-nothing function like: cout << "Now in FunctionOne() \n"; .

Now, this isn't as easy as it sounds, because you can't just write line one, then line two, then line three, of your code. (It won't compile if you do that.) The trick (the fun part, actually) is figuring-out which part of code makes sense to work on next.

Compilers can easily get confused when threre's an error (or two). Sometimes they will point to the wrong line. Sometimes one real error will cause the compiler to report several errors. Link errors are even trickier to track down.

So, it really helps to test-run and test-compile after every one or two lines. As you gain experience, you can write whole functions before testing. But, as you gain experience your programs generally will get longer and more complex, so you still won't be writing the whole program before testing & debugging.

Originally Posted by nekkron

Code:

{ 
  int x = 0;  
  while ( x => 0 ) {
    cout<< x << endl;
  }
}

While loop will go on forever because value of x never changes. So x == 0 all the time, and so it continues to loop.
Oh and that's a syntax error. => should be >=.
endl is the same as '\n' figuratively speaking, because they do the same thing - print a new line.

For your functions, I'd say get rid of them. Just do normal +, -, * and /. The thing is also that just because you pass a and b to the functions, local copies are made and you never store the result so, it's kindof like this:

Code:

int a = 1, b = 2;
a + b;

See? You never store the result, so a and b will never change.

Thanks, thats starting to make sense now. Still a little bit puzzled about using a loop though, i'm still testing out various functions and what they can do, so hopefully I can find a way to do it all.

EDIT: I've found a use for the 'for' loop, and this script isn't meant for it, the 'while' works perfect, with some more addons i've done more functions so my new code is like this:

Code:

#include <iostream>
#include <string>

using namespace std;

int main()
{
	string answer;
	string name;
	string e1;
	string build;
	int x(100); // char base hp
	int y(30); // enemy base hp
	int a(2); // char base blo.
	int b(5); // char base att.
	int c(1); // char secondary blo.
	int d(4); // char secondary att.


	cout<<"what is your name? ";
	cin>>name;
	cout<<"what would you like to call the enemy? ";
	cin>>e1;
	cout<<"what stat build would you prefer?\n";
	cout<<"build 1: +5 att. +1 block. +20 hp.\n";
	cout<<"build 2: +1 att. +3 block. +40 hp.\n";
	cout<<"build 3: +3 att. +5 block. +60 hp.\n";
	cin>>build;
	if (build=="1"||"build 1") {
		(b=10); // inc. att. +5
		(a=3); // inc. blo. +1
		(d=9); // inc. secondary att. +4
		(c=2); // inc. secondart blo. +0
		(x=120); // inc. hp +20
	while (x >= 1&&y >= 1) {
	cout<<"do you want to hit or block "<<e1<<"? ";
	cin>>answer;
	if (answer=="hit") {
			cout<<e1<<" recieved "<<(b)<<" damage\n";
			cout<<name<<" revieved "<<(a)<<" damge\n";
			(--x);
			(--x);
			(--x);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
	}
	else if (answer=="block") {
			cout<<e1<<" recieved "<<(d)<<" damage\n";
			cout<<name<<" revieved "<<(c)<<" damge\n";
			(--x);
			(--x);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
	}
	else {
		cout<<"please use only hit or block\n";
	}
	cout<<"\n";
	cout<<name<<" has "<<(x)<<" health remaining\n";
	cout<<e1<<" has "<<(y)<<" health remaining\n";
	cout<<"\n";
	}
	}
	cin.get();
}

My full script, has 3 different character builds, and I'm still unable to work out how to update the stat variables based on which character build I choose, they all seem to use the first build. I think perhaps a 'while' loop with 'do' constraint would work, but i'm not sure. So more trial and error for me. But thanks for the info it works fine.

Your indentation still needs some improvement. For example, that if... it's hard for me to see where it actually ends because you've failed to indent the code in that block properly.
The rule is to always do indention at each new block (things that begin with { and end with }).
Now, as for the code...

Originally Posted by nekkron

Code:

	int x(100); // char base hp
	int y(30); // enemy base hp
	int a(2); // char base blo.
	int b(5); // char base att.
	int c(1); // char secondary blo.
	int d(4); // char secondary att.

I'm assuming you're initializing these variables? I'd rather prefer to see int x = 100, because it's much clearer what you're trying to do. I almost mistook it that you wanted to write an array. So think about it a little.

Code:

	if (build=="1"||"build 1") {

If doesn't quite work that way.
It's If (condition1 || condition2). That line might just give you a warning, because "build 1" is a const char*, which is always != 0, thus always true. Thus the IF will always execute. You should do if (build == "1" || build == "build 1") or something depending on what you want.

Code:

		(b=10); // inc. att. +5
		(a=3); // inc. blo. +1
		(d=9); // inc. secondary att. +4
		(c=2); // inc. secondart blo. +0
		(x=120); // inc. hp +20

This does not do what you think it does. It assigns 10 b, 3 to a, 9 to d, 2 to c and 120 to x. If you want to increase it, just do a += 3 or a = a +3 (basic math!). And use better variables names. b, a, d, c, x... well, they just don't tell me anything that's stored in those variables at all.

Code:

			(--x);
			(--x);
			(--x);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);

I'm also confused, besides what cpjust mentioned, why you decrement those variables so many times. Also, basic math applies here as well: y = y - 10 or y -= 10.

Code:

			(--x);
			(--x);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);
			(--y);

Same here...