The C/C++ Preprocessor

[White_Eskimo]

Well, it defiently took me a long time to write this tutorial...it covers the preprocessor and what it does and how to use it. Also, this tutorial will cover how to make comments in C++ using preprocessor directives. We will learn how to write named macros and parameterized macros and how to make header files and how to use them in your programs. Because i was bored, at the end i included all of the Escape Characters i could think up of and i made a list of books that helped me learn C++ when i was young and that i would recommend. Anyways, download the .zip file and unzip it. Then open up Pre-processor.doc. If you don't have Microsoft Word, just save it as a Rich Text File (.rtf). The tutorial is pretty long, 7 pages to be exact, but i think it is worth reading. Anyways, enjoy guys...i spent a lot of my weekend writing this

[slarty]

Nice tutorial. Anyway I'm going to be a pedantic bastard as usual

const int PI = 3.141592654;

How exactly is an int going to contain a number which isn't an integer then? Does your compiler not give this as an error?

#include <iostream.h>

Shouldn't we use iostream these days (as numerous other threads have mentioned) ? And std::cout ? Just like Mr. Stroustrup tells us to?

Cheers

Slarty

[White_Eskimo]

const int PI = 3.141592654;

slatry, thanks for pointing that out...lol i meant to type

const double PI = 3.141592654;

damn that was an embarrassing mistake...well when you type a tutorial that long you gotta make a small errors like that orelse you are too perfect to be human...

#include <iostream.h>

Yes, once again you are correct, but i didnt feel like doing it Because i was using the #define directive a lot, i thought it might have confused the reader if my code looked like:

#include <iostream>
using std::cout;
using std::endl;
using std::cin;
#define PI 3.141592654

more lines that i just didnt need (although it might have made my code a little bit more up to date)...both ways work correctly. If you have any questions about the using directives, feel free to PM me slarty...

by the way----sorry memorY

[Al76484]

Nice tutorial. I have been teaching my nephew the basics of C++ programming. This doc was a valuable read for him. (Although even he pointed out that an integer cannot store decimal places! - obviously some of the basics I have already taught him have sunk in).

Thanks for spending your time to help others.

Cheers for now,
Al76484

[Fred Brown]

Great tutorial W.Eskimo. I'm learning some good stuff. Thanks. When the next one coming out?

Freddy

[White_Eskimo]

When the next one coming out?

well i dont know what to write my next one about...i have already covered pointers and reading/writting to files. Anyways if you have anything that you want to learn, maybe i already know it, just let me know and ill write one up

[kryptonite0110]

you said header files end with the extention of .h but they very well can end with .hpp... otherwise it is a great tutorial...

you also wrote:

#define CUBE(x) (x*x*x)

when i think it should be:

#define CUBE(x) ((x)*(x)*(x))

because it would be bad practice. Consider the following:

#define x 2 + 4
#define CUBE (x*x*x)

then your code would look like this after the preproccessor looks at it
instead of CUBE (x*x*x)
it would be CUBE (2+4*2+4*2+4)
the answer you would be looking for is not (2+4*2+4*2+4) but ((2+4)*(2+4)*(2+4))

if that explanation makes any sense... that is just somthing that annoys me a lot.

[White_Eskimo]

#include <iostream.h>
#define CUBE(x) (x*x*x)

int main (void)
{
	double x;
	x=2;
	cout << x << " cubed ";
	cout << "is " << CUBE(x);
}

you are correct kryptonite but if you look at the example, x is just 2.0 so my there wont be any confusion. However, if the programmer was lame enough to add #define x 2+4 to his code, then he will not get the answer he had expected. In the tutorial i explained the importance of parenthesis. I didnt need to do #define CUBE(x) ((x)*(x)*(x)) because i was just multiplying 2.0 with itself 3 times, but like you said, if i wanted to multiply 2+4 together 3 times, i should have added parenthesis.

[Tedob1]

Damme White_Eskimo that really is one hell of a tutorial. Very nice work.

Thanks!

[positivemayhem]

well whatever .. i gess its gonna be a nice one .. am gonna mail to mah home .. yeap thut means me'z workin from me wrkplce.