Get a match function working.

src/matcher.erl

@@ -3,7 +3,7 @@
 -behaviour(gen_server).
 
 %% API
--export([add_sequence/1, start_link/0]).
+-export([add/1, match/2, start_link/0]).
 
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
@@ -24,8 +24,11 @@
 start_link() ->
   gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
 
-add_sequence(Seq) ->
-  gen_server:call(?SERVER, {add_sequence, Seq}).
+add(Seq) ->
+  gen_server:call(?SERVER, {add, Seq}).
+
+match(Seq, Degree) ->
+  gen_server:call(?SERVER, {match, Seq, Degree}).
 
 %%====================================================================
 %% gen_server callbacks
@@ -51,12 +54,23 @@ init([]) ->
 %%                                      {stop, Reason, State}
 %% Description: Handling call messages
 %%--------------------------------------------------------------------
-handle_call({add_sequence, Seq}, _From, State) ->
+handle_call({add, Seq}, _From, State) ->
+  %% TODO: Remove magic numbers.
   L1 = mg_util:combinations(Seq, 1),
   L2 = mg_util:combinations(Seq, 2),
   Reply = ets:insert(?TABLE, [{X, Seq} || X <- L1++L2]),
   {reply, Reply, State};
 
+handle_call({match, Seq, Degree}, _From, State) ->
+  Cs = mg_util:combinations(Seq, Degree),
+  Ms = lists:foldl(fun(C, Acc) ->
+                       ets:lookup(?TABLE, C) ++ Acc
+                   end, [], Cs),
+  Reply = length(lists:filter(fun(Elt) -> 
+                                  mg_util:is_mutation(Seq, Elt)
+                              end, Ms)),
+  {reply, Reply, State};
+
 handle_call(_Request, _From, State) ->
   Reply = ok,
   {reply, Reply, State}.

src/mg_util.erl

@@ -1,6 +1,8 @@
 -module(mg_util).
 
--export([combinations/2]).
+-export([combinations/2, is_mutation/2]).
+
+-define(POINT, $$).
 
 combinations(Seq, Degree) when Degree > 1 ->
   L = lists:foldr(fun (Elt, Acc) -> combinations(Elt, 1) ++ Acc end,
@@ -11,9 +13,27 @@ combinations(Seq, 1) ->
   F = fun (Pos, Acc) ->
           Head = lists:sublist(Seq, Pos - 1),
           Tail = lists:nthtail(Pos, Seq),
-          [Head ++ "$" ++ Tail | Acc]
+          [Head ++ [?POINT] ++ Tail | Acc]
       end,
   lists:filter(fun(X) when X =:= Seq -> false;
                   (_) -> true
                end,
                lists:foldr(F, [], lists:seq(1, length(Seq)))).
+
+is_mutation(Seq1, {_, Seq2}) when Seq1 =:= Seq2 ->
+  false;
+is_mutation(Seq1, {_, Seq2}) when length(Seq1) =/= length(Seq2) ->
+  false;
+is_mutation(Seq1, {Key, Seq2}) ->
+  only_differs_at_points(Seq1, Key, Seq2).
+
+only_differs_at_points([], [], []) ->
+  true;
+only_differs_at_points([C|_], [?POINT|_], [C|_]) ->
+  false;
+only_differs_at_points([_|As], [?POINT|Ks], [_|Bs]) ->
+  only_differs_at_points(As, Ks, Bs);
+only_differs_at_points([C|As], [_|Ks], [C|Bs]) ->
+  only_differs_at_points(As, Ks, Bs);
+only_differs_at_points(_,_,_) ->
+  false.