# Runes

The Runes module provides enhanced `Map` and `Array` implementations that return `Option` types instead of `undefined` or `-1` for operations that might not find a value.

## $map

Creates a `RunicMap` instance with Option-returning methods.

```typescript
import { $map } from 'funkcia/runes';

const map = $map([
  ['key1', 'value1'],
  ['key2', 'value2'],
]);

// Returns Option<string> instead of string | undefined
const value = map.get('key1');
// Some('value1')

const missing = map.get('key3');
// None
```

## $array

Creates a `RunicArray` instance with Option-returning methods.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array([1, 2, 3]);

// Returns Option<number> instead of number | undefined
const item = arr.at(0);
// Some(1)

const missing = arr.at(10);
// None
```

### RunicArray

An `Array` subclass with Option-returning methods for safer array operations.

#### at

Returns `Some` with the item at the specified index if it exists, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array([1, 2, 3]);

const first = arr.at(0);
// Some(1)

const last = arr.at(-1);
// Some(3)

const missing = arr.at(10);
// None
```

#### find

Returns `Some` with the first element matching the predicate, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array([1, 2, 3, 4, 5]);

const even = arr.find((n) => n % 2 === 0);
// Some(2)

const large = arr.find((n) => n > 10);
// None
```

#### findIndex

Returns `Some` with the index of the first element matching the predicate, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array(['a', 'b', 'c']);

const index = arr.findIndex((item) => item === 'b');
// Some(1)

const missing = arr.findIndex((item) => item === 'z');
// None
```

#### indexOf

Returns `Some` with the index of the first occurrence of a value, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array(['a', 'b', 'c', 'b']);

const index = arr.indexOf('b');
// Some(1)

const missing = arr.indexOf('z');
// None
```

#### lastIndexOf

Returns `Some` with the index of the last occurrence of a value, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array(['a', 'b', 'c', 'b']);

const index = arr.lastIndexOf('b');
// Some(3)
```

#### pop

Removes and returns `Some` with the last element if it exists, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array([1, 2, 3]);

const last = arr.pop();
// Some(3)
// arr is now [1, 2]

const empty = $array<number>([]);
const nothing = empty.pop();
// None
```

#### shift

Removes and returns `Some` with the first element if it exists, otherwise `None`.

```typescript
import { $array } from 'funkcia/runes';

const arr = $array([1, 2, 3]);

const first = arr.shift();
// Some(1)
// arr is now [2, 3]
```


---

# 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://funkcia.lukemorales.io/modules/runes.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.