Thread: Tell me about C/C++

Actually I have a question...

I'm learning C++ and right now I'm reading about ++ and --

The example it gives me is this...

Example 1:

Code:

B=3;
A=++B;
// A contains 4, B contains 4

Example 2:

Code:

B=3;
A=B++;
// A contains 3, B contains 4

I don't really understand the whole ++ and -- and how it affects the A and B variables. Can someone explain how it adds up?

Edit: Also, how does all this make up a video game engine?

increment and decrement
(Ie. add one, or subtract one)
used all the time when looping and keeping count of things

a++ means "return the value of a, and then increment it"
++a means "increment a, then return the value"

subtle (but important) differences, however the differences between the pre & post incrementation are only important if you care about the value of a variable mid-operation

Code:

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

}

and

Code:

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

}

are identical in operation
(because we do not care about the value of 'i' mid-operation

however,
say we are keeping a count of something that we later need to step back through in reverse

Code:

void increment_something(int var)
{
    old_var = var++;
}

here, we do care about the value of var mid-operation, therefore we store the "old value" of var and increment var

You can of course do this

Code:

void increment_something(int var)
{
    old_var = var;
    var++;
}

then we've split the operation into two
and now we no longer care about the return value of the increment

Originally Posted by Ynot

Code:

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

}

and

Code:

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

}

are identical in operation
(because we do not care about the value of 'i' mid-operation

Almost correct. In for loops you want to do the latter because in order to return, then increment, it has to keep a copy of it. Not a problem with ints, but with objects it can.

++ and -- are weird to learn.

b = ++a; is like this:
a = a + 1;
b = a;

b = a++; is like this:
b = a;
a = a + 1;

Err...you're using some things in there I haven't learned yet. So I think you just made it more confusing for me...

Edit: Ok that makes it a little easier to understand...

So would it be something like this for the 2nd part?

b = 1;
b = a++;

Would the result be: b = 1, a = 2? Because I already defined b to equal 1 and then a equals b which is 1, then I add a to a to get 2, right?

follow a tutorial on C++
I've always liked this one
http://www.cprogramming.com/tutorial/lesson1.html

It'll take you through the basics, and slowly build up to more complex things

*edit*
Just realised you're not the OP.....

Lol no I'm not

But I'll make good use of this thread...

Also, I'm following this tutorial so far: http://cplusplus.com/doc/tutorial/operators/

edit: but again, how does all this make up a video game engine? Or any program?

Well, we break it up. We break down the seemingly huge task of a full program and break it down into pieces which are more manageable. We then code each part, sometimes sticking the together in one executable, but more commonly, we create a complex set of dynamic libraries.

A video game engine would probably be about a quarter of a million lines of C++ code, broken up into maybe 1000 different files.

Wow...quarter of a million...

Well I guess that adds up fast seeing how small lines of code are.

A Roxxor wants me to make a simple text based game. I'm not sure how I'm going to do this...