stdlib additions

2 files changed, 66 insertions, 2 deletions

diff --git a/gen/list.erl b/gen/list.erl
index a5df23e..1567b98 100644
--- a/gen/list.erl
+++ b/gen/list.erl
@@ -2,7 +2,7 @@
 -compile(no_auto_import).
 -include_lib("eunit/include/eunit.hrl").
 
--export([length/1, reverse/1, is_empty/1, has_member/2, head/1, tail/1, filter/2, map/2, traverse/2, drop/2, take/2, new/0, append/2, flatten/1, foldl/3, foldr/3]).
+-export([length/1, reverse/1, is_empty/1, has_member/2, head/1, tail/1, filter/2, map/2, traverse/2, drop/2, take/2, new/0, append/2, flatten/1, foldl/3, foldr/3, find/2]).
 
 length(A) ->
     erlang:length(A).
@@ -264,3 +264,32 @@ foldr(List, Acc, Fun) ->
 foldr_test() ->
     expect:equal(foldr([1, 2, 3], [], fun(X, Acc) -> [X | Acc] end), [1, 2, 3]).
 -endif.
+
+find(Haystack, F) ->
+    case Haystack of
+        [] ->
+            {error, not_found};
+
+        [X | Rest] ->
+            case F(X) of
+                {ok, X1} ->
+                    {ok, X1};
+
+                _ ->
+                    find(Rest, F)
+            end
+    end.
+
+-ifdef(TEST).
+find_test() ->
+    F = fun(X) -> case X of
+            2 ->
+                {ok, 4};
+
+            _ ->
+                {error, not_found}
+        end end,
+    expect:equal(find([1, 2, 3], F), {ok, 4}),
+    expect:equal(find([1, 3, 2], F), {ok, 4}),
+    expect:equal(find([1, 3], F), {error, not_found}).
+-endif.
diff --git a/gen/tuple.erl b/gen/tuple.erl
index 270bb29..ec38901 100644
--- a/gen/tuple.erl
+++ b/gen/tuple.erl
@@ -2,7 +2,16 @@
 -compile(no_auto_import).
 -include_lib("eunit/include/eunit.hrl").
 
--export([first/1, second/1]).
+-export([new/2, first/1, second/1, swap/1, fetch/2]).
+
+new(A, B) ->
+    {A, B}.
+
+-ifdef(TEST).
+new_test() ->
+    expect:equal(new(1, 2), {1, 2}),
+    expect:equal(new(2, <<"3">>), {2, <<"3">>}).
+-endif.
 
 first(Tup) ->
     {A, _} = Tup,
@@ -21,3 +30,29 @@ second(Tup) ->
 second_test() ->
     expect:equal(second({1, 2}), 2).
 -endif.
+
+swap(Tup) ->
+    {A, B} = Tup,
+    {B, A}.
+
+-ifdef(TEST).
+swap_test() ->
+    expect:equal(swap({1, <<"2">>}), {<<"2">>, 1}).
+-endif.
+
+fetch(Haystack, Needle) ->
+    list:find(Haystack, fun(Tuple) -> case first(Tuple) =:= Needle of
+                      true ->
+                          {ok, second(Tuple)};
+
+                      false ->
+                          {error, []}
+                  end end).
+
+-ifdef(TEST).
+fetch_test() ->
+    Proplist = [{0, <<"1">>}, {1, <<"2">>}],
+    expect:equal(fetch(Proplist, 0), {ok, <<"1">>}),
+    expect:equal(fetch(Proplist, 1), {ok, <<"2">>}),
+    expect:is_error(fetch(Proplist, 2)).
+-endif.