Overview

Directly writing constants into our code is referred to as using magic numbers.

We try to avoid this lol

C lang

Example

Bad - wtf is 52?

for (int i = 0; i < 52; i++) {
 // deal card
}

Better, but introduces another problem
- What if some other function manipulates this number?

int deck_size = 52;
for (int i = 0; i < deck_size; i++) {
 // deal card
}

Best
- C has a preprocessor directive (also called a macro) for creating symbolic constants
- Use preprocessor directives!

#define DECK_SIZE 52
 
... // some code
 
for (int i = 0; i < DECK_SIZE; i++) {
 // deal card
}

Preprocessor Directives

#define NAME REPLACEMENT
#define PI 3.14159265

At the time your program is compiled, #define goes through your code and replaces NAME with REPLACEMENT
if #include is similar to copy/paste, then #define is analogous to find/replace
NO semicolon!
Convention
- All caps to make it clear that it’s a constant and not a variable