wip

src/wfc_sentence.erl

@@ -0,0 +1,75 @@
+% @doc a sentence is an ordset of words
+%
+% in "A + B + AB", this is the full expression
+%
+% summation is implied in a sentence
+%
+% empty sentence is 0
+-module(wfc_sentence).
+
+-export_type([
+    sentence/0
+]).
+
+-export([
+    %% constructors
+    zero/0,
+    validate/1,
+    from_list/1, to_list/1,
+    %% ops
+    add/2, add/1
+]).
+
+-opaque sentence() :: {s, ordsets:ordset(wfc_word:word())}.
+
+%%--------------------------
+%% constructors
+%%--------------------------
+
+-spec zero() :: sentence().
+
+zero() ->
+    {s, []}.
+
+
+-spec from_list(Words) -> Result
+    when Words  :: [wfc_word:word()],
+         Result :: {ok, sentence()}
+                 | {error, string()}.
+
+from_list(Words) ->
+    from_list(ordsets:from_list(Words), []).
+
+%% validate each word
+from_list([W | Rest], Acc) ->
+    case wfc_word:validate(W) of
+        ok    -> from_list(Rest, [W | Acc]);
+        Error -> Error
+    end;
+% done, all good
+from_list([], Acc) ->
+    {ok, {s, lists:reverse(Acc)}}.
+
+
+
+-spec to_list(sentence()) -> Result
+    when Result :: {ok, [wfc_word:word()]}
+                 | {error, string()}.
+
+to_list({s, Words}) -> {ok, Words};
+to_list(Bad)        -> {error, wfc_utils:str("wfc_sentence:to_list: bad sentence: ~tp", [Bad])}.
+
+
+%%---------------------------
+%% prim ops
+%%---------------------------
+
+add({s, X}, {s, Y}) -> {s, disjoint_union(X, Y)}.
+
+disjoint_union(X, Y) ->
+    ordsets:subtract(ordsets:union(X, Y),
+                     ordsets:intersection(X, Y)).
+
+
+add([S | Rest]) -> add(S, add(Rest));
+add([])         -> zero().