X-Git-Url: https://git.xandkar.net/?a=blobdiff_plain;f=src%2Fhope_list.erl;h=f179d1a054a2dabb46351eef14bf81e64aa9bc8f;hb=a626cf31904f7d782c8c9756adc4279b0dd5db66;hp=9ce451e927d454940d3dca236266492dd6b61051;hpb=17b5d686d1b6c608c8fab801f44701bb0c6cccf3;p=hope.git

diff --git a/src/hope_list.erl b/src/hope_list.erl
index 9ce451e..f179d1a 100644
--- a/src/hope_list.erl
+++ b/src/hope_list.erl
@@ -6,13 +6,92 @@
 
 -export(
     [ unique_preserve_order/1
+    , map/2
+    , map/3  % Tunable recursion limit
+    , map_rev/2
+    , map_slow/2
+    , first_match/2
     ]).
 
 
+-define(DEFAULT_RECURSION_LIMIT, 1000).
+
+
 -type t(A) ::
     [A].
 
 
+%% @doc Tail-recursive equivalent of lists:map/2
+%% @end
+-spec map([A], fun((A) -> (B))) ->
+    [B].
+map(Xs, F) ->
+    map(Xs, F, ?DEFAULT_RECURSION_LIMIT).
+
+-spec map([A], fun((A) -> (B)), RecursionLimit :: non_neg_integer()) ->
+    [B].
+map(Xs, F, RecursionLimit) ->
+    map(Xs, F, RecursionLimit, 0).
+
+map([], _, _, _) ->
+    [];
+map([X1], F, _, _) ->
+    Y1 = F(X1),
+    [Y1];
+map([X1, X2], F, _, _) ->
+    Y1 = F(X1),
+    Y2 = F(X2),
+    [Y1, Y2];
+map([X1, X2, X3], F, _, _) ->
+    Y1 = F(X1),
+    Y2 = F(X2),
+    Y3 = F(X3),
+    [Y1, Y2, Y3];
+map([X1, X2, X3, X4], F, _, _) ->
+    Y1 = F(X1),
+    Y2 = F(X2),
+    Y3 = F(X3),
+    Y4 = F(X4),
+    [Y1, Y2, Y3, Y4];
+map([X1, X2, X3, X4, X5 | Xs], F, RecursionLimit, RecursionCount) ->
+    Y1 = F(X1),
+    Y2 = F(X2),
+    Y3 = F(X3),
+    Y4 = F(X4),
+    Y5 = F(X5),
+    Ys =
+        case RecursionCount > RecursionLimit
+        of  true  -> map_slow(Xs, F)
+        ;   false -> map     (Xs, F, RecursionLimit, RecursionCount + 1)
+        end,
+    [Y1, Y2, Y3, Y4, Y5 | Ys].
+
+
+%% @doc lists:reverse(map_rev(L, F))
+%% @end
+-spec map_slow([A], fun((A) -> (B))) ->
+    [B].
+map_slow(Xs, F) ->
+    lists:reverse(map_rev(Xs, F)).
+
+
+%% @doc Tail-recursive alternative to lists:map/2, which accumulates and
+%% returns list in reverse order.
+%% @end
+-spec map_rev([A], fun((A) -> (B))) ->
+    [B].
+map_rev(Xs, F) ->
+    map_rev_acc(Xs, F, []).
+
+-spec map_rev_acc([A], fun((A) -> (B)), [B]) ->
+    [B].
+map_rev_acc([], _, Ys) ->
+    Ys;
+map_rev_acc([X|Xs], F, Ys) ->
+    Y = F(X),
+    map_rev_acc(Xs, F, [Y|Ys]).
+
+
 -spec unique_preserve_order(t(A)) ->
     t(A).
 unique_preserve_order(L) ->
@@ -24,3 +103,13 @@ unique_preserve_order(L) ->
             end
         end,
     lists:reverse(lists:foldl(PrependIfNew, [], L)).
+
+-spec first_match([{Tag, fun((A) -> boolean())}], A) ->
+    hope_option:t(Tag).
+first_match([], _) ->
+    none;
+first_match([{Tag, F} | Tests], X) ->
+    case F(X)
+    of  true  -> {some, Tag}
+    ;   false -> first_match(Tests, X)
+    end.