- [x] Attributed variables using the SICStus Prolog interface and
semantics. Adding coroutines like `dif/2`, `freeze/2`, etc.
is straightforward with attributed variables.
- ... * [x] Support for `verify_attributes/3`
- ... * [x] Support for `attribute_goals/2` and `project_attributes/2`
- ... * [x] `call_residue_vars/2`
+ - [x] Support for `verify_attributes/3`
+ - [x] Support for `attribute_goals/2` and `project_attributes/2`
+ - [x] `call_residue_vars/2`
- [x] `if_` and related predicates, following the developments of the
paper "Indexing `dif/2`".
- [x] All-solutions predicates (`findall/{3,4}`, `bagof/3`, `setof/3`, `forall/2`).