________________________________________________________________________

This file is part of Logtalk <https://logtalk.org/>  
SPDX-FileCopyrightText: 1998-2023 Paulo Moura <pmoura@logtalk.org>  
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
________________________________________________________________________


% start by loading the example:

| ?- logtalk_load(predicate_lookups(loader)).
...


% when sending a message to a prototype, the lookup for the predicate
% declaration starts at the prototype itself; therefore, the following
% message is valid:

| ?- bike::frame(Material).

Material = aluminum
yes

% when a prototype doesn't contain a declaration for the predicate in
% the message, the lookup continues in the prototype parent(s):

| ?- bike::where(Where).

Where = land
yes

% when sending a message to a prototype, the lookup for the predicate
% definition starts at the prototype itself:

| ?- mountain_bike::frame(Material).

Material = carbon
yes

% when a prototype doesn't contain a definition for the predicate in
% the message, the lookup continues in the prototype parent(s):

| ?- mountain_bike::crewed.

yes

% we can use the built-in reflection predicates to query about predicate
% declarations and definitions; for example:

| ?- mountain_bike::current_predicate(Predicate).

Predicate = crewed/0 ;
Predicate = frame/1 ;
Predicate = where/1 ;
no

| ?- mountain_bike::predicate_property(frame(_), Property).

Property = logtalk ;
Property = scope(public) ;
Property =  (public) ;
Property = static ;
Property = declared_in(bike) ;
Property = declared_in(bike, 37) ;
Property = defined_in(mountain_bike) ;
Property = defined_in(mountain_bike, 49) ;
Property = redefined_from(bike) ;
Property = redefined_from(bike, 39) ;
Property = number_of_clauses(1) ;
Property = number_of_rules(0)
yes


% when sending a message to an instance, the lookup for the predicate
% declaration starts at the instance class; therefore, the following
% message is valid:

| ?- paraglider::structure(Structure).

Structure = soft
yes

% note that the lookup for the predicate definition starts in the
% instance itself, resulting in the `structure(soft)` answer; 

% when the instance class doesn't contain a declaration for the predicate
% in the message, the lookup continues in the class superclasses; therefore,
% the following message is also valid:

| ?- sailplane::purpose(Purpose).

Purpose = fun
yes

% when the instance doesn't contain a definition for the predicate in the
% message, the lookup continues in the class and, if not found there, in
% the class superclasses:

| ?- sailplane::structure(Structure).

Structure = rigid
yes

% we can use the built-in reflection predicates to query about predicate
% declarations and definitions; for example:

| ?- sailplane::current_predicate(Predicate).

Predicate = purpose/1 ? ;
Predicate = structure/1 ? ;
no

| ?- sailplane::predicate_property(purpose(_), Property).

Property = logtalk ? ;
Property = scope(public) ? ;
Property = public ? ;
Property = static ? ;
Property = declared_in(artificial) ? ;
Property = declared_in(artificial,40) ? ;
Property = defined_in(sailplane) ? ;
Property = defined_in(sailplane,74) ? ;
Property = redefined_from(aircraft) ? ;
Property = redefined_from(aircraft,53) ? ;
Property = number_of_clauses(1) ? ;
Property = number_of_rules(0)
yes
