pushing fewd

2025-09-29 11:52:59 -07:00
parent 5e559b540b
commit 91f0064a5b
3 changed files with 39 additions and 41 deletions
@@ -0,0 +1,83 @@
+% @doc called ltr to disambiguate from 
+%
+% mathematically, this is a variable like "a", "b", "c", etc
+-module(wfc_ltr).
+
+-export_type([
+    ltr/0
+]).
+
+-export([
+    validate/1,
+    from_binary/1, to_binary/1
+]).
+
+% @doc
+% a character is binary data that would be a valid atom
+%
+% [a-z][A-Za-z0-9_]+
+%
+% - leads with lowercase letter
+% - underscores ok
+% - numbers ok
+% - no non-ascii chars
+
+-opaque ltr() :: {c, binary()}.
+
+%%-----------------------
+%% constructors/destructors
+%%-----------------------
+
+-spec validate(Ltr) -> Result
+    when Ltr    :: ltr(),
+         Result :: ok
+                 | {error, Reason :: string()}.
+% @doc validate if a candidate ltr is well-formed and the inner binary is
+% legal
+
+validate({c, Binary}) ->
+    case from_binary(Binary) of
+        {ok, {c, X}} when X =:= Binary ->
+            ok;
+        Error ->
+            Error
+    end;
+validate(Term) ->
+    Error = wfc_utils:emsg("wfc_ltr:validate failed; malformed ltr: ~p", [Term]),
+    {error, Error}.
+
+
+-spec from_binary(Binary) -> Result
+    when Binary :: binary(),
+         Result :: {ok, ltr()}
+                 | {error, Reason :: string()}.
+% @doc
+% make sure the binary is a legal ltr and wrap it in a {c, Binary} tuple
+% @end
+
+%% initial char must be [a-z]
+from_binary(<<L:8, Rest/binary>>) when $a =< L, L =< $z ->
+    new2(<<L>>, Rest);
+from_binary(Char = <<L:8, _/binary>>) ->
+    {error, wfc_utils:emsg("wfc_ltr:from_binary(~p): illegal lead character: ~p", [Char, L])};
+from_binary(Char) ->
+    wfc_utils:err("wfc_ltr:from_binary(~p): malformed argument", [Char]).
+
+%% rest must be [A-Za-z0-9_]
+new2(Acc, <<L:8, Rest/binary>>) when       ($A =< L andalso L =< $Z)
+                                    orelse ($a =< L andalso L =< $z)
+                                    orelse ($0 =< L andalso L =< $9)
+                                    orelse (L =:= $_) ->
+    new2(<<Acc/binary, L>>, Rest);
+new2(Acc, <<>>) ->
+    {ok, {c, Acc}};
+new2(Acc, Rest = <<BadChar:8, _/binary>>) ->
+    WholeChar = <<Acc/binary, Rest/binary>>,
+    Error     = wfc_utils:emsg("wfc_ltr:new2(~p, ~p): illegal character in ltr: ~p; WholeChar: ~p", [Acc, Rest, BadChar, WholeChar]),
+    {error, Error}.
+
+
+
+-spec to_binary(ltr()) -> binary().
+
+to_binary({c, X}) -> X.