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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(recipes(loader)). yes

% list all the ingredients required for the green soup recipe:

| ?- green_soup::ingredients(Ingredients). Ingredients = [peas,cream,water,oil] yes

% list all the steps required to make mashed peas:

| ?- mashed_peas::steps(Steps). Steps = [1-'Boil the peas.',2-'Mash the peas',3-'Add salt and mix.'] yes

% find out what dishes you can cook with green peas (we check that % we have a ground recipe to skip the generic recipe represented % by the recipe/3 parametric object):

| ?- conforms_to_protocol(Recipe, recipep), ground(Recipe), Recipe::ingredient(peas). Recipe = green_soup ? ; Recipe = mashed_peas ? ; no

% patch the prototypical recipe to add a level/1 descriptor to all recipes:

| ?- logtalk_load(recipes(patch_1)). yes

% recipes are now easy by default:

| ?- mashed_peas::level(Level). Level = easy yes

% but you always get into trouble while making green soup; add a second patch % to define the level value for this recipe to be "hard":

| ?- logtalk_load(recipes(patch_2)). yes

| ?- green_soup::level(Level). Level = hard yes

% when using a mixed representation, the conforms_to_protocol/2 built-in % predicate is not ideal to enumerate recipes as it will also return the % parametric object used for accessing recipes represented as Prolog facts:

| ?- conforms_to_protocol(Recipe, recipep). Recipe = green_soup ; Recipe = mashed_peas ; Recipe = recipe(_, _, _) ; no

% thus, to enumerate recipes, is best to use the recipe/1 predicate, which % ensures that we always get a proper recipe:

Recipe = green_soup ; Recipe = mashed_peas ; Recipe = recipe('Chocolate Chip Cookies', [flour-500-gr, butter-20-gr, chocolate-200-gr, sugar-65-gr, eggs-2-units], ['mix flour, butter and sugar'-10-min, 'add eggs and mix'-10-min, 'make chocolate chips'-5-min, 'split in small portions'-5-min, 'cook in the oven'-25-min]) ; Recipe = recipe('Berries and cream', [cream-500-ml, sugar-50-gr, strawberries-300-gr, chocolate-100-gr], ['mix whipping cream add sugar'-5-min, 'slice strawberries'-5-min, 'place alternate layers of cream and strawberries in dessert dishes'-10-min, 'make chocolate chips'-5-min, 'top dishes with chocolate chips'-5-min]) ; no

% an usage example of the recipe/1 predicate would be:

| ?- recipe(Recipe), Recipe::cooking_time(CookingTime). Recipe = green_soup, CookingTime = 36 ; Recipe = mashed_peas, CookingTime = 16 ; Recipe = recipe('Chocolate Chip Cookies', [flour-500-gr, butter-20-gr, chocolate-200-gr, sugar-65-gr, eggs-2-units], ['mix flour, butter and sugar'-10-min, 'add eggs and mix'-10-min, 'make chocolate chips'-5-min, 'split in small portions'-5-min, 'cook in the oven'-25-min]), CookingTime = 55 ; Recipe = recipe('Berries and cream', [cream-500-ml, sugar-50-gr, strawberries-300-gr, chocolate-100-gr], ['mix whipping cream add sugar'-5-min, 'slice strawberries'-5-min, 'place alternate layers of cream and strawberries in dessert dishes'-10-min, 'make chocolate chips'-5-min, 'top dishes with chocolate chips'-5-min]), CookingTime = 30 ; no