product-of-empty-list-of-numbers-could-return-1

Author: inoas

CHANGELOG.md

@@ -5,6 +5,9 @@
 - The `list` module gains the `group` function.
 - The `dynamic` module is able to decode simple JavaScript objects to maps.
   So, the behaviour of the `field` and `object` functions are consistent.
+- For a given empty list as an argument `int.product` now returns `1` instead
+  of `0` and `float.product` now returns `1.0` instead of `1.0`. This mimicks
+  the behavior of Elixir's `Enum.product/1`.
 
 ## v0.26.0 - 2023-01-12
 

src/gleam/float.gleam

@@ -427,7 +427,7 @@ fn do_sum(numbers: List(Float), initial: Float) -> Float {
 ///
 pub fn product(numbers: List(Float)) -> Float {
   case numbers {
-    [] -> 0.0
+    [] -> 1.0
     _ -> do_product(numbers, 1.0)
   }
 }

src/gleam/int.gleam

@@ -465,7 +465,7 @@ fn do_sum(numbers: List(Int), initial: Int) -> Int {
 ///
 pub fn product(numbers: List(Int)) -> Int {
   case numbers {
-    [] -> 0
+    [] -> 1
     _ -> do_product(numbers, 1)
   }
 }

test/gleam/float_test.gleam

@@ -338,7 +338,7 @@ pub fn sum_test() {
 
 pub fn product_test() {
   float.product([])
-  |> should.equal(0.0)
+  |> should.equal(1.0)
 
   float.product([4.0])
   |> should.equal(4.0)

test/gleam/int_test.gleam

@@ -349,7 +349,7 @@ pub fn sum_test() {
 
 pub fn product_test() {
   int.product([])
-  |> should.equal(0)
+  |> should.equal(1)
 
   int.product([4])
   |> should.equal(4)