Add from/to_list and at functions

src/glearray.gleam

@@ -1,9 +1,28 @@
 pub type Array(a)
 
 @external(erlang, "glearray_ffi", "new")
-@external(javascript, "./glearray_ffi.mjs", "new_array")
+@external(javascript, "./glearray_ffi.mjs", "newArray")
 pub fn new() -> Array(a)
 
+@external(erlang, "erlang", "list_to_tuple")
+@external(javascript, "./glearray_ffi.mjs", "fromList")
+pub fn from_list(list: List(a)) -> Array(a)
+
+@external(erlang, "erlang", "tuple_to_list")
+@external(javascript, "./gleam.mjs", "toList")
+pub fn to_list(array: Array(a)) -> List(a)
+
 @external(erlang, "erlang", "tuple_size")
-@external(javascript, "./glearray_ffi.mjs", "array_length")
-pub fn length(array: Array(a)) -> Int
+@external(javascript, "./glearray_ffi.mjs", "arrayLength")
+pub fn length(of array: Array(a)) -> Int
+
+pub fn at(in array: Array(a), get index: Int) -> Result(a, Nil) {
+  case index >= 0 && index < length(array) {
+    True -> Ok(do_at(array, index))
+    False -> Error(Nil)
+  }
+}
+
+@external(erlang, "glearray_ffi", "at")
+@external(javascript, "./glearray_ffi.mjs", "at")
+fn do_at(array: Array(a), index: Int) -> a

src/glearray_ffi.erl

@@ -1,5 +1,7 @@
 -module(glearray_ffi).
 
--export([new/0]).
+-export([new/0, at/2]).
 
 new() -> {}.
+
+at(Array, Index) -> element(Index + 1, Array).

src/glearray_ffi.mjs

@@ -1,7 +1,15 @@
-export function new_array() {
+export function newArray() {
   return [];
 }
 
-export function array_length(array) {
+export function fromList(list) {
+  return list.toArray();
+}
+
+export function arrayLength(array) {
   return array.length;
 }
+
+export function at(array, index) {
+  return array[index];
+}

test/glearray_test.gleam

@@ -1,13 +1,60 @@
+import gleam/list
 import gleeunit
 import gleeunit/should
-import glearray
+import glearray.{type Array}
 
 pub fn main() {
   gleeunit.main()
 }
 
 pub fn empty_array_test() {
-  glearray.new()
+  assert_empty(glearray.new())
+}
+
+pub fn from_to_list_test() {
+  []
+  |> glearray.from_list
+  |> assert_empty
+  |> glearray.to_list
+  |> should.equal([])
+
+  let list = [1, 2, 3, -8, 8954]
+  list
+  |> glearray.from_list
+  |> assert_length(5)
+  |> glearray.to_list
+  |> should.equal(list)
+}
+
+pub fn at_test() {
+  let list = ["a", "B", "fdsau", "rh3892wfd", "äèëå亣", "Another ONE!"]
+  let array = glearray.from_list(list)
+  list.index_map(
+    list,
+    fn(index, element) {
+      array
+      |> glearray.at(index)
+      |> should.equal(Ok(element))
+    },
+  )
+
+  glearray.at(array, -1)
+  |> should.be_error
+  glearray.at(array, glearray.length(array))
+  |> should.be_error
+  glearray.at(array, 100)
+  |> should.be_error
+}
+
+fn assert_empty(array: Array(a)) -> Array(a) {
+  assert_length(array, 0)
+  should.equal(array, glearray.new())
+  array
+}
+
+fn assert_length(array: Array(a), length: Int) -> Array(a) {
+  array
   |> glearray.length
-  |> should.equal(0)
+  |> should.equal(length)
+  array
 }