prolog_metainference.pl -- Infer meta-predicate properties

This module infers meta-predicate properties by inspecting the clauses of predicates that call other predicates. This is extremely useful for program analysis and refactoring because many programs `in the wild' have incomplete or incorrect meta-predicate information.

See also

- This library is used by prolog_walk_code/1 to improve the accuracy of this analysis.

To be done

- Re-introduce some alias-analysis

- Not all missing meta-declarations are interesting. Notably, meta-predicates that are private and only pass meta-arguments on behalve of a public meta-predicates do not need a declaration.

 inferred_meta_predicate(:Head, ?MetaSpec) is nondet

True when MetaSpec is an inferred meta-predicate specification for Head.

 infer_meta_predicate(:Head, -MetaSpec) is semidet

True when MetaSpec is a meta-predicate specifier for the predicate Head. Derived meta-predicates are collected and made available through inferred_meta_predicate/2.

 meta_pred_args_in_clause(+Module, +Head, -MetaSpec) is nondet[private]

 annotate_meta_vars_in_body(+Term, +Module) is det[private]

Annotate variables in Term if they appear as meta-arguments.

To be done

- Aliasing. Previous code detected aliasing for

• =/2
• functor/3
• atom_concat/3
• =../2
• arg/3

- We can make this nondet, exploring multiple aliasing paths in disjunctions.

 annotate_meta_args(+Arg, +Arity, +Goal, +MetaSpec, +Module)[private]

 meta_annotation(+Head, -Annotation) is semidet[private]

True when Annotation is an appropriate meta-specification for Head.

 meta_arg(+AnnotatedArg, -MetaSpec) is det[private]

True when MetaSpec is a proper annotation for the argument AnnotatedArg. This is simple if the argument is a plain argument in the head (first clause). If it is a compound term, it must unify to _:_, otherwise there is no point turning it into a meta argument. If the module part is then passed to a module sensitive predicate, we assume it is a meta-predicate.

 combine_meta_args(+Heads, -Head) is det[private]

Combine multiple meta-specifications.