wip

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])}.