# 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")
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://hadeslang.gitbook.io/doc/language-spec/other/preprocessor-statements.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.