---
sidebar_position: 7
title: List
---

### make
```
List.make: (number, 'a) => list<'a>
```
Returns an array of size ``n`` filled with value ``e``. 

```js
List.make(4, 1) // creates the list [1, 1, 1, 1]
```

See [Rescript implementation](https://rescript-lang.org/docs/manual/latest/api/belt/array#make)

### toString
```
toString: (list<'a>) => string
```

### length
```
length: (list<'a>) => number
```

### up to
```
List.upTo: (low:number, high:number) => list<number>
```
```js
List.upTo(0, 5) // creates the list [0, 1, 2, 3, 4, 5]
```

Syntax taken from [Ruby](https://apidock.com/ruby/v2_5_5/Integer/upto). 

### first
```
first: (list<'a>) => 'a
```

### last
```
last: (list<'a>) => 'a
```

### reverse
```
reverse: (list<'a>) => list<'a>
```

### map
```
map: (list<'a>, a => b) => list<'b>
```

See [Rescript implementation](https://rescript-lang.org/docs/manual/latest/api/belt/array#map).

### reduce
```
reduce: (list<'b>, 'a, ('a, 'b) => 'a) => 'a 
```
``reduce(arr, init, f)``

Applies ``f`` to each element of ``arr``. The function ``f`` has two paramaters, an accumulator and the next value from the array.

```js
reduce([2, 3, 4], 1, {|acc, value| acc + value}) == 10
```

See [Rescript implementation](https://rescript-lang.org/docs/manual/latest/api/belt/array#reduce).

### reduce reverse
```
reduceReverse: (list<'b>, 'a, ('a, 'b) => 'a) => 'a 
```

Works like ``reduce``, but the function is applied to each item from the last back to the first.

See [Rescript implementation](https://rescript-lang.org/docs/manual/latest/api/belt/array#reducereverse).