Fix type-driven encode, more docs

README.md

@@ -29,6 +29,10 @@ Main API:
 * `serialize_typed(template(), term()) -> binary()`
 * `deserialize(binary()) -> term()`
 
+In the examples below, we use the `decode` functions, to illustrate
+how the type information is represented. The fully serialized form is
+produced by the `serialize` functions.
+
 The basic types supported by the encoder are:
 * `non_neg_integer()` (`int`   , code: 248)
 * `binary()`          (`binary`, code: 249)
@@ -88,16 +92,23 @@ Template-driven encoding
 ----
 
 Templates can be provided to the encoder by either naming an already registered
-type, or by passing a template directly. The template will then be enforced, and
-used to slightly compress the encoding.
+type, or by passing a template directly. In both cases, the encoder will enforce
+the type information in the template.
 
-In the following example, as the encoder knows that `{11,12}` is encoded as a
-tuple of two integers, it can omit the inner type tags.
+If the template has been registered, the encoder omits inner type tags (still
+inserting the top-level tag), leading to some compression of the output.
+This also means that the serialized term cannot be decoded without the same
+schema information on the decoder side.
+
+In the case of a directly provided template, all type information is inserted,
+such that the serialized term can be decoded without any added type information.
+The template types are still enforced during encoding.
 
 ```erlang
 ET = fun(Type,Term) -> io:fwrite("~w~n", [gmser_dyn:encode_typed(Type,Term)]) end.
 
-ET({int,int}, {11,12}) ->[<<0>>,<<1>>,[<<253>>,[<<11>>,<<12>>]]]
-ET({int,int}, {11,a}) ->
-** exception error: {illegal,int,a} ...
+ET([{int,int}], [{1,2}]) -> [<<0>>,<<1>>,[<<251>>,[[[<<248>>,<<1>>],[<<248>>,<<2>>]]]]]
+
+gmser_dyn:register_type(1000,lt2i,[{int,int}]).
+ET(lt2i, [{1,2}]) -> [<<0>>,<<1>>,[<<3,232>>,[[<<1>>,<<2>>]]]]
 ```