/* Part of SWI-Prolog
Author: Eva Stoewe, Guenter Kniesel and Jan Wielemaker
E-mail: pdt@lists.iai.uni-bonn.de
WWW: http://sewiki.iai.uni-bonn.de/research/pdt/start
Copyright (c) 2004-2012, CS Dept. III, University of Bonn
All rights reserved.
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modification, are permitted provided that the following conditions
are met:
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notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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*/
:- module(prolog_metainference,
[ infer_meta_predicate/2, % :Head, -MetaSpec
inferred_meta_predicate/2 % :Head, ?MetaSpec
]).
:- autoload(library(apply),[maplist/4]).
:- autoload(library(lists),[append/3]).
:- meta_predicate
inferred_meta_predicate(:, ?),
infer_meta_predicate(:, -).
:- dynamic
inferred_meta_pred/3. % Head, Module, Meta
/** <module> 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 This library is used by prolog_walk_code/1 to improve the
accuracy of this analysis.
@tbd Re-introduce some alias-analysis
@tbd 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.
inferred_meta_predicate(M:Head, MetaSpec) :-
inferred_meta_pred(Head, M, MetaSpec).
inferred_meta_predicate(M:Head, MetaSpec) :-
predicate_property(M:Head, imported_from(From)),
inferred_meta_pred(Head, From, MetaSpec).
%! 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.
infer_meta_predicate(Head, MetaSpec) :-
inferred_meta_predicate(Head, MetaSpec),
!.
infer_meta_predicate(M:Head, MetaSpec) :-
predicate_property(M:Head, imported_from(From)),
!,
do_infer_meta_predicate(From:Head, MetaSpec),
assertz(inferred_meta_pred(Head, From, MetaSpec)).
infer_meta_predicate(M:Head, MetaSpec) :-
do_infer_meta_predicate(M:Head, MetaSpec),
assertz(inferred_meta_pred(Head, M, MetaSpec)).
:- meta_predicate
do_infer_meta_predicate(:, -).
do_infer_meta_predicate(Module:AHead, MetaSpec):-
functor(AHead, Functor, Arity),
functor(Head, Functor, Arity), % Generalise the head
findall(MetaSpec,
meta_pred_args_in_clause(Module, Head, MetaSpec),
MetaSpecs),
MetaSpecs \== [],
combine_meta_args(MetaSpecs, MetaSpec).
%! meta_pred_args_in_clause(+Module, +Head, -MetaSpec) is nondet.
meta_pred_args_in_clause(Module, Head, MetaArgs) :-
clause(Module:Head, Body),
annotate_meta_vars_in_body(Body, Module),
meta_annotation(Head, MetaArgs).
%! annotate_meta_vars_in_body(+Term, +Module) is det
%
% Annotate variables in Term if they appear as meta-arguments.
%
% @tbd Aliasing. Previous code detected aliasing for
% - =/2
% - functor/3
% - atom_concat/3
% - =../2
% - arg/3
% @tbd We can make this nondet, exploring multiple aliasing
% paths in disjunctions.
annotate_meta_vars_in_body(A, _) :-
atomic(A),
!.
annotate_meta_vars_in_body(Var, _) :-
var(Var),
!,
annotate(Var, 0).
annotate_meta_vars_in_body(Module:Term, _) :-
!,
( atom(Module)
-> annotate_meta_vars_in_body(Term, Module)
; var(Module)
-> annotate(Module, m)
; true % may continue if Term is a system
). % predicate?
annotate_meta_vars_in_body((TermA, TermB), Module) :-
!,
annotate_meta_vars_in_body(TermB, Module),
annotate_meta_vars_in_body(TermA, Module).
annotate_meta_vars_in_body((TermA; TermB), Module) :-
!,
annotate_meta_vars_in_body(TermB, Module),
annotate_meta_vars_in_body(TermA, Module).
annotate_meta_vars_in_body((TermA->TermB), Module) :-
!,
annotate_meta_vars_in_body(TermB, Module),
annotate_meta_vars_in_body(TermA, Module).
annotate_meta_vars_in_body((TermA*->TermB), Module) :-
!,
annotate_meta_vars_in_body(TermB, Module),
annotate_meta_vars_in_body(TermA, Module).
annotate_meta_vars_in_body(A=B, _) :-
var(A), var(B),
!,
A = B.
annotate_meta_vars_in_body(Goal, Module) :- % TBD: do we trust this?
predicate_property(Module:Goal, meta_predicate(Head)),
!,
functor(Goal, _, Arity),
annotate_meta_args(1, Arity, Goal, Head, Module).
annotate_meta_vars_in_body(Goal, Module) :-
inferred_meta_predicate(Module:Goal, Head),
!,
functor(Goal, _, Arity),
annotate_meta_args(1, Arity, Goal, Head, Module).
annotate_meta_vars_in_body(_, _).
%! annotate_meta_args(+Arg, +Arity, +Goal, +MetaSpec, +Module)
annotate_meta_args(I, Arity, Goal, MetaSpec, Module) :-
I =< Arity,
!,
arg(I, MetaSpec, MetaArg),
arg(I, Goal, Arg),
annotate_meta_arg(MetaArg, Arg, Module),
I2 is I + 1,
annotate_meta_args(I2, Arity, Goal, MetaSpec, Module).
annotate_meta_args(_, _, _, _, _).
annotate_meta_arg(Spec, Arg, _) :-
var(Arg),
!,
annotate(Arg, Spec).
annotate_meta_arg(0, Arg, Module) :-
!,
annotate_meta_vars_in_body(Arg, Module).
annotate_meta_arg(N, Arg, Module) :-
integer(N),
callable(Arg),
!,
Arg =.. List,
length(Extra, N),
append(List, Extra, ListX),
ArgX =.. ListX,
annotate_meta_vars_in_body(ArgX, Module).
annotate_meta_arg(Spec, Arg, _) :-
is_meta(Spec),
compound(Arg),
Arg = Module:_,
var(Module),
!,
annotate(Module, m).
annotate_meta_arg(_,_,_).
annotate(Var, Annotation) :-
get_attr(Var, prolog_metainference, Annot0),
!,
join_annotation(Annot0, Annotation, Joined),
put_attr(Var, prolog_metainference, Joined).
annotate(Var, Annotation) :-
put_attr(Var, prolog_metainference, Annotation).
join_annotation(A, A, A) :- !.
join_annotation(A, B, C) :-
( is_meta(A), \+ is_meta(B)
-> C = A
; \+ is_meta(A), is_meta(B)
-> C = B
; is_meta(A), is_meta(B)
-> C = (:)
; C = *
).
attr_unify_hook(A0, Other) :-
get_attr(Other, prolog_metainference, A1),
!,
join_annotation(A0, A1, A),
put_attr(Other, prolog_metainference, A).
%! meta_annotation(+Head, -Annotation) is semidet.
%
% True when Annotation is an appropriate meta-specification for
% Head.
meta_annotation(Head, Meta) :-
functor(Head, Name, Arity),
functor(Meta, Name, Arity),
meta_args(1, Arity, Head, Meta, HasMeta),
HasMeta == true.
meta_args(I, Arity, Head, Meta, HasMeta) :-
I =< Arity,
!,
arg(I, Head, HeadArg),
arg(I, Meta, MetaArg),
meta_arg(HeadArg, MetaArg),
( is_meta(MetaArg)
-> HasMeta = true
; true
),
I2 is I + 1,
meta_args(I2, Arity, Head, Meta, HasMeta).
meta_args(_, _, _, _, _).
is_meta(I) :- integer(I), !.
is_meta(:).
is_meta(^).
is_meta(//).
%! meta_arg(+AnnotatedArg, -MetaSpec) is det.
%
% 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.
meta_arg(HeadArg, MetaArg) :-
get_attr(HeadArg, prolog_metainference, MetaArg),
MetaArg \== m,
!.
meta_arg(HeadArg, :) :-
compound(HeadArg),
HeadArg = M:_,
get_attr(M, prolog_metainference, m),
!.
meta_arg(_, *).
%! combine_meta_args(+Heads, -Head) is det.
%
% Combine multiple meta-specifications.
combine_meta_args([], []) :- !.
combine_meta_args([List], List) :- !.
combine_meta_args([Spec,Spec|Specs], CombinedArgs) :-
!,
combine_meta_args([Spec|Specs], CombinedArgs).
combine_meta_args([Spec1,Spec2|Specs], CombinedArgs) :-
Spec1 =.. [Name|Args1],
Spec2 =.. [Name|Args2],
maplist(join_annotation, Args1, Args2, Args),
Spec =.. [Name|Args],
combine_meta_args([Spec|Specs], CombinedArgs).