Add trim func tests. Begin combinatorial funcs impl

src/gleam_community/maths/float_list.gleam

@@ -54,6 +54,7 @@ import gleam/option
 import gleam_community/maths/float as floatx
 import gleam_community/maths/int as intx
 import gleam/io
+import gleam/iterator
 
 /// <div style="text-align: right;">
 ///     <a href="https://github.com/gleam-community/maths/issues">
@@ -645,7 +646,7 @@ pub fn sum(arr: List(Float)) -> Float {
 ///
 pub fn product(arr: List(Float)) -> Float {
   case arr {
-    [] -> 0.0
+    [] -> 1.0
     _ ->
       arr
       |> list.fold(1.0, fn(acc: Float, a: Float) -> Float { a *. acc })

src/gleam_community/maths/int_list.gleam

@@ -192,7 +192,7 @@ pub fn sum(arr: List(Int)) -> Int {
 ///
 pub fn product(arr: List(Int)) -> Int {
   case arr {
-    [] -> 0
+    [] -> 1
     _ ->
       arr
       |> list.fold(1, fn(acc: Int, a: Int) -> Int { a * acc })

src/gleam_community/maths/list.gleam

@@ -81,3 +81,90 @@ pub fn trim(arr: List(a), min: Int, max: Int) -> Result(List(a), String) {
       }
   }
 }
+
+/// <div style="text-align: right;">
+///     <a href="https://github.com/gleam-community/maths/issues">
+///         <small>Spot a typo? Open an issue!</small>
+///     </a>
+/// </div>
+///
+/// Generate all $$k$$-combinations based on a given list.
+///
+/// <details>
+///     <summary>Example:</summary>
+///
+///     import gleeunit/should
+///     import gleam/list
+///     import gleam_community/maths/float_list
+///
+///     pub fn example () {
+///     }
+/// </details>
+///
+/// <div style="text-align: right;">
+///     <a href="#">
+///         <small>Back to top ↑</small>
+///     </a>
+/// </div>
+///
+pub fn combination(arr: List(a), k: Int) -> List(a) {
+  todo
+}
+
+/// <div style="text-align: right;">
+///     <a href="https://github.com/gleam-community/maths/issues">
+///         <small>Spot a typo? Open an issue!</small>
+///     </a>
+/// </div>
+///
+/// Generate all permutations based on a given list.
+///
+/// <details>
+///     <summary>Example:</summary>
+///
+///     import gleeunit/should
+///     import gleam/list
+///     import gleam_community/maths/float_list
+///
+///     pub fn example () {
+///     }
+/// </details>
+///
+/// <div style="text-align: right;">
+///     <a href="#">
+///         <small>Back to top ↑</small>
+///     </a>
+/// </div>
+///
+pub fn permutation(arr: List(a)) -> List(a) {
+  todo
+}
+
+/// <div style="text-align: right;">
+///     <a href="https://github.com/gleam-community/maths/issues">
+///         <small>Spot a typo? Open an issue!</small>
+///     </a>
+/// </div>
+///
+/// Generate a list containing all combinations of one element from each of two given lists.
+///
+/// <details>
+///     <summary>Example:</summary>
+///
+///     import gleeunit/should
+///     import gleam/list
+///     import gleam_community/maths/float_list
+///
+///     pub fn example () {
+///     }
+/// </details>
+///
+/// <div style="text-align: right;">
+///     <a href="#">
+///         <small>Back to top ↑</small>
+///     </a>
+/// </div>
+///
+pub fn cartesian_product(xarr: List(a), yarr: List(a)) -> List(a) {
+  todo
+}

test/gleam/gleam_community_maths_float_list_test.gleam

@@ -481,7 +481,7 @@ pub fn float_list_product_test() {
   // An empty list returns 0
   []
   |> float_list.product()
-  |> should.equal(0.0)
+  |> should.equal(1.0)
 
   // Valid input returns a result
   [1.0, 2.0, 3.0]

test/gleam/gleam_community_maths_int_list_test.gleam

@@ -105,7 +105,7 @@ pub fn int_list_product_test() {
   // An empty list returns 0
   []
   |> int_list.product()
-  |> should.equal(0)
+  |> should.equal(1)
 
   // Valid input returns a result
   [1, 2, 3]

test/gleam/gleam_community_maths_list_test.gleam

@@ -0,0 +1,22 @@
+import gleam/int
+import gleam/list
+import gleam/pair
+import gleam_community/maths/list as listx
+import gleeunit
+import gleeunit/should
+
+pub fn main() {
+  gleeunit.main()
+}
+
+pub fn list_trim_test() {
+  // An empty lists returns an error
+  []
+  |> listx.trim(0, 0)
+  |> should.be_error()
+
+  // Trim the list to only the middle part of list
+  [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
+  |> listx.trim(1, 4)
+  |> should.equal(Ok([2.0, 3.0, 4.0, 5.0]))
+}