Merge pull request #23 from inaka/ktn_lists.delete_first

added ktn_lists:delete_first/2

Makefile

@@ -10,7 +10,7 @@ include erlang.mk
 
 COMPILE_FIRST = ktn_recipe
 
-CT_SUITES = ktn_maps ktn_recipe ktn_numbers ktn_binary
+CT_SUITES = ktn_maps ktn_recipe ktn_numbers ktn_binary ktn_lists
 
 shell: app
 	erl -pa ebin -pa deps/*/ebin -s sync

src/ktn_lists.erl

@@ -0,0 +1,22 @@
+-module(ktn_lists).
+
+-export([
+         delete_first/2
+        ]).
+
+%% @doc Returns a copy of List deleting the first Element where Fun(Element)
+%%      returns true, if there is such an element.
+%% @end
+-spec delete_first(fun((term()) -> boolean()), list()) -> list().
+delete_first(Fun, List) ->
+  delete_first(Fun, List, []).
+
+delete_first(Fun, [], Acc) when is_function(Fun, 1) ->
+  lists:reverse(Acc);
+delete_first(Fun, [Head | Tail], Acc) ->
+  case Fun(Head) of
+    false ->
+      delete_first(Fun, Tail, [Head | Acc]);
+    true -> 
+      lists:concat([lists:reverse(Acc), Tail])
+  end.

test/ktn_lists_SUITE.erl

@@ -0,0 +1,54 @@
+-module(ktn_lists_SUITE).
+
+-export([
+         all/0,
+         init_per_suite/1,
+         end_per_suite/1
+        ]).
+
+-export([
+         delete_first/1
+        ]).
+
+-define(EXCLUDED_FUNS,
+        [
+         module_info,
+         all,
+         test,
+         init_per_suite,
+         end_per_suite
+        ]).
+
+-type config() :: [{atom(), term()}].
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Common test
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+-spec all() -> [atom()].
+all() ->
+    Exports = ?MODULE:module_info(exports),
+    [F || {F, _} <- Exports, not lists:member(F, ?EXCLUDED_FUNS)].
+
+-spec init_per_suite(config()) -> config().
+init_per_suite(Config) ->
+    Config.
+
+-spec end_per_suite(config()) -> config().
+end_per_suite(Config) ->
+    Config.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% Test Cases
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+-spec delete_first(config()) -> ok.
+delete_first(_Config) ->
+    Fun = fun(N) -> 0 == N rem 2 end,
+
+    [] = ktn_lists:delete_first(Fun, []),
+    [] = ktn_lists:delete_first(Fun, [4]),
+    [4] = ktn_lists:delete_first(Fun, [4, 4]),
+    [1, 3] = ktn_lists:delete_first(Fun, [1, 3]),
+    [1, 3] = ktn_lists:delete_first(Fun, [1, 4, 3]),
+    [1, 3, 4] = ktn_lists:delete_first(Fun, [1, 4, 3, 4]).