# Pre Processor

C-style preprocessor running before parsing: macros, conditional compilation, file inclusion.

## Defines

```cpp
#define MAX_HP 100
#define SQUARE(x) ((x) * (x))

int32 hp = MAX_HP;
int32 area = SQUARE(5);  // 25
```

## Conditional Compilation

Directives: `#ifdef`, `#ifndef`, `#else`, `#elif`, `#endif`, `#undef`, `#pragma`.

```cpp
#ifdef DEBUG
    println("debug mode");
#else
    // release mode
#endif
```

Define preprocessor symbols from the SDK:

```cpp
define(engine, "DEBUG", "1");
define(engine, "PLATFORM", "windows");
```

Then use in scripts:

```cpp
#ifdef PLATFORM
    println("platform defined");
#endif
```

## Include

Include another source file. The contents are inserted at the include point.

```cpp
#include "common.em"
#include "types.em"
```

Include paths are configured from the SDK:

```cpp
add_include_path(engine, "includes/");
```


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