The C/C++ Preprocessor

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 :)

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

Quote:

---

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?

Quote:

---

#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

Quote:

---

const int PI = 3.141592654;

---

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

Code:

---

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...

Quote:

---

#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:

Code:

---

#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 :)

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

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

Freddy

Quote:

---

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 :)

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.

Code:

---

#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. :)

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

Thanks!

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.

Thanks for the tutorial. IT really helped me!