Preprocessor Directives

Preprocessor directives are special statements that begin with a pound # sign, and are the only ones that don't need the semi-colon ; at the end.

Preprocessor directives must be in a linear order, and BEFORE the code to keep certain errors from coming up.

There are two important directives:

#include "filename"

Includes a file to be compiled in addition to SYSTEM.VC. This is recommended to have a neat categorizing of your codes. The filename is quotes and must also have the extension at the end of the filename with it.

Example:
```
#include "draw.vc"
```
#define A B

#define is basically a seek-replace statement. Every spot the identifier A is used will be replaced with their value B, which is everything after A until the next line (so B can be an expression, a short piece of code, a symbol, etc). You can use a define like you would a string or int but since their value is substituted wherever they're found, they have a constant value during runtime. It can be used for things such as file paths, debugging code, or keeping track of numeric constants. They are also used in Verge's built-in library as scan codes and color filters, among other things.

Example:
```
#define MAX_PARTY_MEMBERS 5
int party_index[MAX_PARTY_MEMBERS]; 
```

Talkback

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Talkback #1 written by Gayo on 2004-07-15.

A few further notes on #define are warranted.

Order is important for #defines; if I #define MAX_PARTY_MEMBERS to 5, the #define statement must come before any instance of MAX_PARTY_MEMBERS in the code. For this reason, you should put all your #defines before the code that uses them. #included files are read by the compiler in the order in which they are #included, so if you #include a file containing a define, that define is valid for anything below the #include statement (including other #included files), as well as for anything below it in the included file.

The preprocessor will not redefine tokens within other #define statements. That is to say, if I code:



#define A_VALUE 1


#define ANOTHER_VALUE A_VALUE

...the compiler will return an error when trying to evaluate the second statement. A_VALUE is #defined to be 1, but the preprocessor will not change the A_VALUE in the second line since it is within the body of a #define statement.

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