#55 implement remove_item_from_list/2

Author: nelsonic

lib/useful.ex

@@ -129,6 +129,18 @@ defmodule Useful do
     end
   end
 
+  @doc """
+  `remove_item_from_list/2` removes a given `item` from a `list` in any position.
+  """
+  def remove_item_from_list(item, list) do
+    if Enum.member?(list, item) do
+      i = Enum.find_index(list, fn it -> it == item end)
+      List.delete_at(list, i)
+    else
+      list
+    end
+  end
+
   @doc """
   `stringy_map/1` converts a `Map` of any depth/nesting into a string.
   Deeply nested maps are denoted by "__" (double underscore). See flatten_map/1

test/useful_test.exs

@@ -186,6 +186,32 @@ defmodule UsefulTest do
     end
   end
 
+  describe "remove_item_from_list/2" do
+    test "remove_item_from_list/2 removes a numeric item from a list" do
+      list = [1, 2, 3, 4]
+      # tl/1 = "tail of list" hexdocs.pm/elixir/1.15.5/Kernel.html#tl/1
+      assert Useful.remove_item_from_list(1, list) == tl(list)
+    end
+
+    test "remove_item_from_list/2 removes a numeric item in any position" do
+      list = [1, 2, 3, 4]
+      updated_list = [1, 2, 4]
+      assert Useful.remove_item_from_list(3, list) == updated_list
+    end
+
+    test "remove_item_from_list/2 removes an item from the list" do
+      list = ["don't", "panic", "about", "climate", "change"]
+      # tl/1 = "tail of list" hexdocs.pm/elixir/1.15.5/Kernel.html#tl/1
+      assert Useful.remove_item_from_list("don't", list) == tl(list)
+    end
+
+    test "attempt to remove_item_from_list/2 ignores item *not* in list" do
+      item = "save"
+      list = ["AI", "will", "destroy", "us"]
+      assert Useful.remove_item_from_list(item, list) == list
+    end
+  end
+
   describe "stringfy_map/1" do
     test "returns nil string when map is nil" do
       assert Useful.stringify_map(nil) == "nil"