> For the complete documentation index, see [llms.txt](https://hadeslang.gitbook.io/doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hadeslang.gitbook.io/doc/language-spec/other/preprocessor-statements.md).

# Preprocessor statements

## `set` statement

The set statement, sets a preprocessor variable to a value. The values of preprocessor variables are not bound to types. 

```csharp
%set VERSION 0.7.1%
%set APPLICATION_NAME My Application%
```

Some variables are set by the Hades interpreter.

| Variable       | Content                                                                        |
| -------------- | ------------------------------------------------------------------------------ |
| OS             | The operating system, a script is being ran on (can be: NT, Mac, Linux, Other) |
| OS\_VERSION    | The version of the operating system as int (417, 1803, 10136, etc...)          |
| HADES\_VERSION | The version of the Hades interpreter the script is being ran on as int         |
| HAS\_EVAL      | 1 if the Hades runtime has the `eval` function, 0 if not                       |
| HAS\_INTERNALS | 1 if the Hades runtime has the `std:internals` library, 0 if not               |

## `if-else if-fi` statement

The `if-elif-fi` block has a couple special commands to compare values to each other.

| Command | Full name         | Returns true if                                       |
| ------- | ----------------- | ----------------------------------------------------- |
| `eq`    | Equals            | Variables are equal                                   |
| `ne`    | Not equals        | Variables are not equal                               |
| `gt`    | Greater than      | First variable is greater than second variable        |
| `lt`    | Lower than        | First variable is lower than second variable          |
| `ge`    | Greater or equals | First variable is greater or equal to second variable |
| `le`    | Lower or equals   | First variable is lower or equal to second variable   |

```swift
with os from std:os
with console from std:io

var listCommand

%if eq OS Windows%
listCommand = "dir"
%else if eq OS Linux%
listCommand = "ls"
%else%
console.out("OS not recognized!")
os.exit(-1)
&fi%

%if ge OS_VERSION 1803%
os.exec("wslpath 'c:\users'")
%fi%

os.exec(listCommand)
```

## `import` statement

The import statement copies the content of the specified file and pastes it into the source code (works recursively).

### function.hd

```swift
func print(...a)
    for(var arg in a)
        console.out(arg)
    end
end
```

### classDef.hd

{% code title="" %}

```swift
class printer
%import function.hd%
end
```

{% endcode %}

### main.hd

```javascript
with console from std:io

%import classDef.hd%

printer().print("Hello","world")
```

### Result

**main.hd** is being converted to:

```javascript
with console from std:io

class printer
    func print(...a)
        for(var arg in a)
            console.out(arg)
        end
    end
end

printer().print("Hello","world")
```