wfc stuff

src/wfc_word.erl

@@ -0,0 +1,82 @@
+% @doc a word is an ordset of wfchars
+%
+% multiplication is implied in a word
+%
+% empty word is 1
+%
+% anything times itself equals itself, so duplication is ignored
+-module(wfc_word).
+
+-export_type([
+    word/0
+]).
+
+-export([
+    %% constructors
+    one/0,
+    validate/1,
+    from_wfchars/1, to_wfchars/1,
+    %% ops
+    mul/2, mul/1
+]).
+
+-opaque word() :: {w, ordsets:ordset(wfc_wfchar:wfchar())}.
+
+%%----------------------------
+%% constructor
+%%----------------------------
+
+-spec one() -> word().
+
+one() ->
+    {w, []}.
+
+
+validate(_)   -> error(nyi).
+to_wfchars(_) -> error(nyi).
+
+-spec from_wfchars(WfChars) -> Result
+    when WfChars :: list(wfc_char:wfchar()),
+         Result  :: {ok, word()}
+                  | {error, Reason :: string()}.
+
+from_wfchars(Chars) ->
+    from_wfchars(ordsets:from_list(Chars), []).
+
+
+%% validate each char
+from_wfchars([WfChar | Rest], Acc) ->
+    case wfc_wfchar:validate(WfChar) of
+        ok    -> from_wfchars(Rest, [WfChar | Acc]);
+        Error -> Error
+    end;
+% done, all good
+from_wfchars([], Acc) ->
+    {ok, {w, lists:reverse(Acc)}}.
+
+
+%%----------------------------
+%% ops
+%%----------------------------
+
+-spec mul(word(), word()) -> Result
+    when Result :: {ok, word()}
+                 | {error, Reason :: string()}.
+% @doc product of two words
+
+mul({w, X}, {w, Y}) ->
+    case from_wfchars(ordsets:union(X, Y)) of
+        Result = {ok, _} -> Result;
+        Error            -> Error
+    end.
+
+
+-spec mul(Words) -> Result
+    when Words  :: [word()],
+         Result :: {ok, word()}
+                 | {error, Reason},
+         Reason :: string().
+% @doc multiply a list of words together
+
+mul([Word | Rest]) -> mul(Word, mul(Rest));
+mul([])            -> {ok, one()}.