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//
// Copyright (c) 2009-2017 Benjamin Kaufmann
//
// This file is part of Clasp. See http://www.cs.uni-potsdam.de/clasp/
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//
#include "example.h"
// Add the libclasp directory to the list of
// include directoies of your build system.
#include <clasp/logic_program.h> // for defining logic programs
#include <clasp/unfounded_check.h> // unfounded set checkers
#include <clasp/model_enumerators.h>// for enumerating answer sets
#include <clasp/solve_algorithms.h> // for enumerating answer sets
// Compute the stable models of the program
// a :- not b.
// b :- not a.
void example1(bool basicSolve) {
// LogicProgram provides the interface for
// defining logic programs.
// It also preprocesses the program and converts it
// to the internal solver format.
// See logic_program.h for details.
Clasp::Asp::LogicProgram lp;
Potassco::RuleBuilder rb;
// Among other things, SharedContext maintains a Solver object
// which hosts the data and functions for CDNL answer set solving.
// See shared_context.h for details.
Clasp::SharedContext ctx;
// startProgram must be called once before we can add atoms/rules
lp.startProgram(ctx);
// Define the rules of the program.
Potassco::Atom_t a = lp.newAtom();
Potassco::Atom_t b = lp.newAtom();
lp.addRule(rb.start().addHead(a).addGoal(Potassco::neg(b)));
lp.addRule(rb.start().addHead(b).addGoal(Potassco::neg(a)));
// Populate output table.
// The output table defines what is printed for a literal
// that is part of an answer set.
lp.addOutput("a", a);
lp.addOutput("b", b);
// It is not limited to atoms. For example, the following
// statement results in the ouput "~b" whenever b is not
// in a stable model.
lp.addOutput("~b", Potassco::neg(b));
// And we always want to have "eureka"...
lp.addOutput("eureka", Potassco::toSpan<Potassco::Lit_t>());
// Once all rules are defined, call endProgram() to load the (simplified)
// program into the context object.
lp.endProgram();
// Since we want to compute more than one
// answer set, we need an enumerator.
// See enumerator.h for details
Clasp::ModelEnumerator enumerator;
enumerator.init(ctx);
// We are done with problem setup.
// Prepare for solving.
ctx.endInit();
if (basicSolve) {
std::cout << "With Clasp::BasicSolve" << std::endl;
// BasicSolve implements a basic search for a model.
// It handles the various strategies like restarts, deletion, etc.
Clasp::BasicSolve solve(*ctx.master());
// Prepare the solver for enumeration.
enumerator.start(solve.solver());
while (solve.solve() == Clasp::value_true) {
// Make the enumerator aware of the new model and
// let it compute a new constraint and/or backtracking level.
if (enumerator.commitModel(solve.solver())) { printModel(ctx.output, enumerator.lastModel()); }
// Integrate the model into the search and thereby prepare
// the solver for the search for the next model.
enumerator.update(solve.solver());
}
std::cout << "No more models!" << std::endl;
}
else {
std::cout << "With Clasp::SequentialSolve" << std::endl;
// SequentialSolve combines a BasicSolve object,
// which implements search for a model and handles
// various strategies like restarts, deletion, etc.,
// with an enumerator to provide more complex reasoning,
// like enumeration or optimization.
Clasp::SequentialSolve solve;
solve.setEnumerator(enumerator);
// Start the solve algorithm and prepare solver for enumeration.
solve.start(ctx);
// Extract and print models one by one.
while (solve.next()) {
printModel(ctx.output, solve.model());
}
if (!solve.more()) {
std::cout << "No more models!" << std::endl;
}
}
}
void example1() {
example1(true);
example1(false);
}
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