caching works correctly

src/wfc_eval_context.erl

@@ -9,6 +9,7 @@
     default/0,
     default_snowflakes/0,
     define/3,
+    undefine/2,
     resolve_pattern/2,
     resolve_snowflake/2
 ]).
@@ -33,6 +34,7 @@ default() ->
 default_snowflakes() ->
     #{<<"and">>     => fun wfc:mul/1,
       <<"xor">>     => fun wfc:add/1,
+      <<"implies">> => fun snf_implies/1,
       <<"ior">> =>
             fun IOR([S1 | Rest]) ->
                     case IOR(Rest) of
@@ -46,10 +48,6 @@ default_snowflakes() ->
             fun ([S]) -> {ok, sf_not(S)};
                 (Bad) -> {error, wfc_utils:str("not/1: wrong number of arguments: ~p", [Bad])}
             end,
-      <<"implies">> =>
-            fun ([A, B]) -> {ok, sf_implies(A, B)};
-                (Bad)    -> {error, wfc_utils:str("implies/2: wrong number of arguments: ~p", [Bad])}
-            end,
       <<"impliedby">> =>
             fun ([A, B]) -> {ok, sf_impliedby(A, B)};
                 (Bad)    -> {error, wfc_utils:str("impliedby/2: wrong number of arguments: ~p", [Bad])}
@@ -60,6 +58,10 @@ default_snowflakes() ->
             end
      }.
 
+snf_implies([A, B]) -> {ok, sf_implies(A, B)};
+snf_implies(Bad)    -> {error, wfc_utils:str("implies/2: wrong number of arguments: ~p", [Bad])}.
+
+
 sf_ior(A, B) ->
     wfc_sftt:appl_ttf(fun ttf_ior/2, [A, B]).
 
@@ -93,14 +95,18 @@ define(Pat, Sentence, Ctx = #ctx{patterns = OldPatterns}) ->
     NewPatterns = maps:put(Pat, Sentence, OldPatterns),
     {ok, Ctx#ctx{patterns = NewPatterns}}.
 
+undefine(Pat, Ctx = #ctx{patterns = OldPatterns}) ->
+    NewPatterns = maps:remove(Pat, OldPatterns),
+    {ok, Ctx#ctx{patterns = NewPatterns}}.
+
 resolve_pattern(Pat, Ctx = #ctx{patterns = Patterns}) ->
     case maps:find(Pat, Patterns) of
-        error -> {error, wfc_utils:str("wfc_eval_context:resolve_pattern: not found: ~w; context: ~w", [Pat, Ctx])};
+        error -> {error, wfc_utils:str("wfc_eval_context:resolve_pattern: not found: ~s; context: ~w", [Pat, Ctx])};
         Result -> Result
     end.
 
 resolve_snowflake(SF, Ctx = #ctx{snowflakes = Snowflakes}) ->
     case maps:find(SF, Snowflakes) of
-        error -> {error, wfc_utils:str("wfc_eval_context:resolve_snowflake: not found: ~w; context: ~w", [SF, Ctx])};
+        error -> {error, wfc_utils:str("wfc_eval_context:resolve_snowflake: not found: ~s; context: ~w", [SF, Ctx])};
         Result -> Result
     end.