# eval

## Function

Compiles and executes a string script, returning the value of the script's explicit `return` or `exit`.

## Syntax

```bt
eval(source)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| source | String | No | '' | BT source code to be executed. |

## Return value

| Type | Description |
| ------ | ------ |
| Any/Empty | The corresponding value is returned when the script is executed to `return` or `exit`; Empty is returned when normal execution ends or the source code is empty. |

## Example

```bt
result = eval('return 3')

// Output: 3
print result
```

## Notes

- eval shares the global environment of the current VM.
- This capability is suitable for REPL, debugging, and scenarios where dynamic scripting is clearly required.