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Miloslav Ciz 2024-03-30 00:11:50 +01:00
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@ -1113,7 +1113,7 @@ int main()
`#define ARRAY_SIZE 10` creates a macro that can be seen as a constant named `ARRAY_SIZE` which stands for `10`. From this line on any occurence of `ARRAY_SIZE` that the preprocessor encounters in the code will be replaced with `10`. The reason for doing this is obvious -- we respect the [DRY](dry.md) (don't repeat yourself) principle, if we didn't use a constant for the array size and used the direct numeric value `10` in different parts of the code, it would be difficult to change them all later, especially in a very long code, there's a danger we'd miss some. With a constant it is enough to change one line in the code (e.g. `#define ARRAY_SIZE 10` to `#define ARRAY_SIZE 20`).
The macro substitution is literally a copy-paste text replacement, there is nothing very complex going on. This means you can create a nickname for almost anything (for example you could do `#define when if` and then also use `when` in place of `if` -- but it's probably not a very good idea). By convention macro names are to be `ALL_UPPER_CASE` (so that whenever you see an all upper case word in the source code, you know it's a macro).
The macro substitution is literally a glorified copy-paste text replacement, there is nothing very complex going on. This means you can create a nickname for almost anything (for example you could do `#define when if` and then also use `when` in place of `if` -- but it's probably not a very good idea). By convention macro names are to be `ALL_UPPER_CASE` (so that whenever you see an all upper case word in the source code, you know it's a macro).
Macros can optionally take parameters similarly to functions. There are no data types, just parameter names. The usage is demonstrated by the following code: