/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 1985-2024, University of Amsterdam VU University Amsterdam SWI-Prolog Solutions b.v. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright 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 the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 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; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(toplevel_variables, [ print_toplevel_variables/0, verbose_expansion/1, '$replace_toplevel_vars'/4, '$save_toplevel_vars'/1, % +Bindings '$switch_toplevel_mode'/1 % +Mode ]). :- dynamic verbose/0. % define the operator globally :- op(1, fx, user:($)). %! '$replace_toplevel_vars'(+Query0, -Query, +Bindings0, -Bindings) is det. % % These predicates realise reuse of toplevel variables using the % $Var notation. These hooks are normally called by toplevel.pl. % If the user defines rules for these hooks in the user module, % these implementations may be called (or not) to define the % interaction with the user hooks. '$replace_toplevel_vars'(Query, Expanded, Bindings, ExpandedBindings) :- expand_vars(Bindings, Query, Expanded, NewBindings), term_variables(Expanded, Free), delete_bound_vars(Bindings, Free, ExpandedBindings0), '$append'(ExpandedBindings0, NewBindings, ExpandedBindings), ( verbose, Query \=@= Expanded -> print_query(Expanded, ExpandedBindings) ; true ). print_query(Query, Bindings) :- bind_vars(Bindings), writeq(Query), write('.'), nl, fail. % undo bind_vars/2. print_query(_, _). bind_vars([]). bind_vars([Name=Value|Rest]) :- Name = Value, bind_vars(Rest). %! expand_vars(+Bindings, +Query, -Expanded, -NewBindings) is det. % % Replace $Var terms inside Query by the toplevel variable term % and unify the result with Expanded. NewBindings gets Name=Value % terms for toplevel variables that are bound to non-ground terms. % % @error existence_error(answer_variable, Name) expand_vars(Bindings, Query, Expanded, NewBindings) :- current_prolog_flag(toplevel_var_size, Count), Count > 0, !, phrase(expand_vars(Bindings, Query, Expanded), NewBindings). expand_vars(Bindings, Query, Query, Bindings). expand_vars(_, Var, Var) --> { var(Var) }, !. expand_vars(_, Atomic, Atomic) --> { atomic(Atomic) }, !. expand_vars(Bindings, $(Var), Value) --> { name_var(Var, Bindings, Name), ( toplevel_var(Name, Value) -> ! ; throw(error(existence_error(answer_variable, Name), _)) ) }, [ Name = Value ]. expand_vars(Bindings, Term, Expanded) --> { compound_name_arity(Term, Name, Arity), !, compound_name_arity(Expanded, Name, Arity), End is Arity + 1 }, expand_args(1, End, Bindings, Term, Expanded). expand_args(End, End, _, _, _) --> !. expand_args(Arg0, End, Bindings, T0, T) --> { arg(Arg0, T0, V0), arg(Arg0, T, V1), Arg1 is Arg0 + 1 }, expand_vars(Bindings, V0, V1), expand_args(Arg1, End, Bindings, T0, T). name_var(Var, [VarName = TheVar|_], VarName) :- Var == TheVar, !. name_var(Var, [_|T], Name) :- name_var(Var, T, Name). delete_bound_vars([], _, []). delete_bound_vars([H|T0], Free, [H|T1]) :- H = (_Name = Value), v_member(Value, Free), !, delete_bound_vars(T0, Free, T1). delete_bound_vars([_|T0], Free, T1) :- delete_bound_vars(T0, Free, T1). v_member(V, [H|T]) :- ( V == H ; v_member(V, T) ). %! '$save_toplevel_vars'(+Bindings) is det. % % Save toplevel variable bindings. '$save_toplevel_vars'(Bindings) :- ( current_prolog_flag(toplevel_var_size, Count), Count > 0 -> assert_bindings(Bindings) ; true ). assert_bindings([]). assert_bindings([Var = Value|Tail]) :- assert_binding(Var, Value), assert_bindings(Tail). assert_binding(Var, Value) :- ( ( nonvar(Value) ; attvar(Value)) -> update_var(Var, Value) ; true ). update_var(Name, Value) :- current_prolog_flag(toplevel_mode, recursive), !, ( nb_current('$topvar', Bindings), Bindings \== [] -> true ; Bindings = '$topvar'{} ), put_dict(Name, Bindings, Value, NewBindings), b_setval('$topvar', NewBindings). update_var(Name, Value) :- delete_var(Name), set_var(Name, Value). delete_var(Name) :- forall(recorded('$topvar', Name = _, Ref), erase(Ref)). set_var(Name, Value) :- current_prolog_flag(toplevel_var_size, Count), !, ( '$term_size'(Value, Count, _) -> recorda('$topvar', Name = Value, _) ; true ). set_var(Name, Value) :- recorda('$topvar', Name = Value, _). toplevel_var(Var, Binding) :- current_prolog_flag(toplevel_mode, recursive), !, nb_current('$topvar', Bindings), Bindings \== [], get_dict(Var, Bindings, Binding). toplevel_var(Var, Binding) :- recorded('$topvar', Var=Binding). %! '$switch_toplevel_mode'(+Mode) is det. % % Migrate the variable database when switching to a new toplevel % mode. Alternatively we may decide to wipe it as the semantics of % the variables may be slightly different. '$switch_toplevel_mode'(recursive) :- findall(Name-Value, retract_topvar(Name, Value), Pairs), dict_pairs(Bindings, '$topvar', Pairs), b_setval('$topvar', Bindings). '$switch_toplevel_mode'(backtracking) :- ( nb_current('$topvar', Dict), Dict \== [] -> forall(get_dict(Name, Dict, Value), recorda('$topvar', Name = Value, _)) ), nb_delete('$topvar'). retract_topvar(Name, Value) :- recorded('$topvar', Name=Value, Ref), erase(Ref). %! print_toplevel_variables % % Print known bindings for toplevel ($Var) variables. print_toplevel_variables :- ( toplevel_var(Name, Value) *-> format('$~w =~t~12|~p~n', [Name, Value]), fail ; format('No defined toplevel variables~n') ). verbose_expansion(on) :- !, retractall(verbose), asserta(verbose). verbose_expansion(off) :- retractall(verbose).