wip

2

@@ -0,0 +1,110 @@
+% @doc a word is an ordset of ltrs
+%
+% This mathematically is a cluster of letters; so in "A + B + AB", this is one
+% of the summands.
+%
+% multiplication is implied in a word
+%
+% empty word is 1
+%
+% anything times itself equals itself, so duplication is ignored
+%
+% multiplication = inclusive union
+%
+% operations assume all inputs are valid
+-module(wfc_word).
+
+-export_type([
+    word/0
+]).
+
+-export([
+    %% constructors
+    one/0,
+    validate/1,
+    from_list/1, to_list/1,
+    %% ops
+    mul/2, mul/1
+]).
+
+-opaque word() :: {w, ordsets:ordset(wfc_ltr:ltr())}.
+
+%%----------------------------
+%% constructor
+%%----------------------------
+
+-spec one() -> word().
+
+one() ->
+    {w, []}.
+
+
+-spec validate(Word) -> Result
+    when Word   :: word(),
+         Result :: ok
+                 | {error, Reason :: string()}.
+% @doc
+% check each letter in the word for validity
+%
+% also check that word shape is valid
+% @end
+
+validate(W = {w, Letters}) ->
+    case from_list(Letters) of
+        {ok, Result} when Result =:= W ->
+            ok;
+        Error ->
+            Error
+    end;
+validate(X) ->
+    {error, wfc_utils:str("wfc_word:validate: malformed word: ~tp", [X])}.
+
+
+
+-spec to_list(word()) -> Result
+    when Result :: {ok, [wfc_ltr:ltr()]}
+                 | {error, string()}.
+
+to_list({w, Ltrs}) -> {ok, Ltrs};
+to_list(Bad)       -> {error, wfc_utils:str("wfc_word:to_list: bad letter: ~tp", [Bad])}.
+
+
+
+-spec from_list(Ltrs) -> Result
+    when Ltrs :: list(wfc_ltr:ltr()),
+         Result  :: {ok, word()}
+                  | {error, Reason :: string()}.
+
+from_list(Chars) ->
+    from_list(ordsets:from_list(Chars), []).
+
+
+%% validate each letter
+from_list([Ltr | Rest], Acc) ->
+    case wfc_ltr:validate(Ltr) of
+        ok    -> from_list(Rest, [Ltr | Acc]);
+        Error -> Error
+    end;
+% done, all good
+from_list([], Acc) ->
+    {ok, {w, lists:reverse(Acc)}}.
+
+
+%%----------------------------
+%% ops
+%%----------------------------
+
+-spec mul(word(), word()) -> word().
+% @doc product of two words
+%
+% assumes the words are valid
+
+mul({w, X}, {w, Y}) ->
+    {w, ordsets:union(X, Y)}.
+
+
+-spec mul([word()]) -> word().
+% @doc multiply a list of words together
+
+mul([Word | Rest]) -> mul(Word, mul(Rest));
+mul([])            -> one().

src/wfc.erl

@@ -0,0 +1,22 @@
+% @doc
+% porcelain wfc ops
+-module(wfc).
+
+-export_type([
+    sentence/0
+]).
+
+-export([
+    
+    zero/0, one/0,
+    add/1, add/2,
+    mul/1, mul/2
+]).
+
+
+-type sentence() :: wfc_sentence:sentence().
+
+
+%% constructors
+-spec 
+zero() 

src/wfc_ltr.erl

@@ -1,4 +1,9 @@
-% @doc called ltr to disambiguate from 
+% @doc called ltr to disambiguate from "char"
+%
+% In "A + B + AB", this is one of the individual letters.
+%
+% a letter is a binary. atom is more natural representation but this is http,
+% can't be spamming the atoms table.
 %
 % mathematically, this is a variable like "a", "b", "c", etc
 -module(wfc_ltr).
@@ -78,6 +83,9 @@ new2(Acc, Rest = <<BadChar:8, _/binary>>) ->
 
 
 
--spec to_binary(ltr()) -> binary().
+-spec to_binary(ltr()) -> Result
+    when Result :: {ok, binary()}
+                 | {error, string()}.
 
-to_binary({c, X}) -> X.
+to_binary({c, X}) -> {ok, X};
+to_binary(Bad)    -> {error, wfc_utils:str("wfc_ltr:to_binary: bad letter: ~tp", [Bad])}.

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().

src/wfc_utils.erl

@@ -1,10 +1,12 @@
 % @doc misc utility functions
 -module(wfc_utils).
 
--export([err/2, emsg/2]).
+-export([err/2, str/2, emsg/2]).
 
 err(Fmt, Pat) ->
     {error, emsg(Fmt, Pat)}.
 
+str(X, Y) -> emsg(X, Y).
+
 emsg(Fmt, Pat) ->
     unicode:characters_to_list(io_lib:format(Fmt, Pat)).

src/wfc_word.erl

@@ -1,10 +1,17 @@
 % @doc a word is an ordset of ltrs
 %
+% This mathematically is a cluster of letters; so in "A + B + AB", this is one
+% of the summands.
+%
 % multiplication is implied in a word
 %
 % empty word is 1
 %
 % anything times itself equals itself, so duplication is ignored
+%
+% multiplication = inclusive union
+%
+% operations assume all inputs are valid
 -module(wfc_word).
 
 -export_type([
@@ -15,7 +22,7 @@
     %% constructors
     one/0,
     validate/1,
-    from_ltrs/1, to_ltrs/1,
+    from_list/1, to_list/1,
     %% ops
     mul/2, mul/1
 ]).
@@ -32,26 +39,54 @@ one() ->
     {w, []}.
 
 
-validate(_) -> error(nyi).
-to_ltrs(_)  -> error(nyi).
+-spec validate(Word) -> Result
+    when Word   :: word(),
+         Result :: ok
+                 | {error, Reason :: string()}.
+% @doc
+% check each letter in the word for validity
+%
+% also check that word shape is valid
+% @end
 
--spec from_ltrs(Ltrs) -> Result
+validate(W = {w, Letters}) ->
+    case from_list(Letters) of
+        {ok, Result} when Result =:= W ->
+            ok;
+        Error ->
+            Error
+    end;
+validate(X) ->
+    {error, wfc_utils:str("wfc_word:validate: malformed word: ~tp", [X])}.
+
+
+
+-spec to_list(word()) -> Result
+    when Result :: {ok, [wfc_ltr:ltr()]}
+                 | {error, string()}.
+
+to_list({w, Ltrs}) -> {ok, Ltrs};
+to_list(Bad)       -> {error, wfc_utils:str("wfc_word:to_list: bad letter: ~tp", [Bad])}.
+
+
+
+-spec from_list(Ltrs) -> Result
     when Ltrs :: list(wfc_ltr:ltr()),
          Result  :: {ok, word()}
                   | {error, Reason :: string()}.
 
-from_ltrs(Chars) ->
-    from_ltrs(ordsets:from_list(Chars), []).
+from_list(Chars) ->
+    from_list(ordsets:from_list(Chars), []).
 
 
 %% validate each letter
-from_ltrs([Ltr | Rest], Acc) ->
+from_list([Ltr | Rest], Acc) ->
     case wfc_ltr:validate(Ltr) of
-        ok    -> from_ltrs(Rest, [Ltr | Acc]);
+        ok    -> from_list(Rest, [Ltr | Acc]);
         Error -> Error
     end;
 % done, all good
-from_ltrs([], Acc) ->
+from_list([], Acc) ->
     {ok, {w, lists:reverse(Acc)}}.
 
 
@@ -73,3 +108,6 @@ mul({w, X}, {w, Y}) ->
 
 mul([Word | Rest]) -> mul(Word, mul(Rest));
 mul([])            -> one().
+
+
+add(