> For the complete documentation index, see [llms.txt](https://docs.atfinity.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.atfinity.io/rule-language/data-types.md).

# Types and Data Structures

RuLA supports four fundamental types for working with data:

| Type                                                    | Description                            | Example                       |
| ------------------------------------------------------- | -------------------------------------- | ----------------------------- |
| [String](/rule-language/data-types/strings.md)          | Text values                            | `"Hello World"`               |
| [Number](/rule-language/data-types/numbers.md)          | Numeric values (integers and decimals) | `42`, `3.14`                  |
| [List](/rule-language/data-types/lists.md)              | Ordered collections of values          | `['a', 'b', 'c']`             |
| [Dictionary](/rule-language/data-types/dictionaries.md) | Key-value pairs                        | `{'name': 'John', 'age': 30}` |

Each type has its own syntax for creation, specific operators for manipulation, and built-in functions for common operations.

## Quick Reference

### Creating Values

```
"This is a string"      # String
42                      # Number
3.14159                 # Number
['apple', 'banana']     # List
{'x': 1, 'y': 2}        # Dictionary
```

### Common Operations

| Operation           | Strings                                                   | Numbers | Lists                                                             | Dictionaries                                                |
| ------------------- | --------------------------------------------------------- | ------- | ----------------------------------------------------------------- | ----------------------------------------------------------- |
| Length              | [`LEN`](/rule-language/operators/string-operators/len.md) | -       | [`COUNT`](/rule-language/operators/list-operators/count.md)       | [`COUNT`](/rule-language/operators/list-operators/count.md) |
| Check if empty      | `LEN(text) == 0`                                          | -       | `list == []`                                                      | `dict == {}`                                                |
| Access by index/key | `text[index]`                                             | -       | `list[index]`                                                     | `dict[key]`                                                 |
| Check containment   | `text contains "x"`                                       | -       | [`contains`](/rule-language/operators/list-operators/contains.md) | [`in`](/rule-language/operators/dictionary-operators/in.md) |


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