Declare predicates to suspend on certain modes. The argument is,
like meta_predicate/1, a comma-separated list of modes
(BlockSpecs). Calls to the predicate is suspended if at least one
of the conditions implies by a blockspec evaluated to true. A
blockspec evaluated to true iff all arguments specified as `-' are
unbound.
Multiple BlockSpecs for a single predicate can appear in one or more
:- block declarations. The predicate is suspended untill all mode
patterns that apply to it are satisfied.
The implementation is realised by creating a wrapper that checks the
block conditions and either calls the original predicate immediately
(if none of the block conditions were true) or uses attributed
variables to delay re-evaluating the block condition until any of
the arguments in question are bound.
- Compatibility
- - SICStus Prolog
