278 lines
9.5 KiB
C++
278 lines
9.5 KiB
C++
#ifndef __ANTHEM__STATEMENT_VISITOR_H
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#define __ANTHEM__STATEMENT_VISITOR_H
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#include <anthem/AST.h>
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#include <anthem/ASTCopy.h>
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#include <anthem/Body.h>
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#include <anthem/Head.h>
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#include <anthem/RuleContext.h>
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#include <anthem/Term.h>
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#include <anthem/Utils.h>
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namespace anthem
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{
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////////////////////////////////////////////////////////////////////////////////////////////////////
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//
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// StatementVisitor
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//
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////////////////////////////////////////////////////////////////////////////////////////////////////
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// Replaces empty and 1-element conjunctions in the antecedent of normal-form formulas
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inline void reduce(ast::Implies &implies)
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{
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if (!implies.antecedent.is<ast::And>())
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return;
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auto &antecedent = implies.antecedent.get<ast::And>();
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// Use “true” as the consequent in case it is empty
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if (antecedent.arguments.empty())
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implies.antecedent = ast::Formula::make<ast::Boolean>(true);
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else if (antecedent.arguments.size() == 1)
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implies.antecedent = std::move(antecedent.arguments[0]);
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////
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struct StatementVisitor
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{
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void visit(const Clingo::AST::Program &program, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &, Context &context)
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{
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context.logger.log(output::Priority::Debug, statement.location) << "reading program “" << program.name << "”";
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if (std::strcmp(program.name, "base") != 0)
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throw LogicException(statement.location, "program parts currently unsupported");
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if (!program.parameters.empty())
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throw LogicException(statement.location, "program parameters currently unsupported");
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}
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void visit(const Clingo::AST::Rule &rule, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &scopedFormulas, Context &context)
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{
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context.logger.log(output::Priority::Debug, statement.location) << "reading rule";
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RuleContext ruleContext;
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ast::VariableStack variableStack;
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variableStack.push(&ruleContext.freeVariables);
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// Collect all head terms
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rule.head.data.accept(HeadLiteralCollectFunctionTermsVisitor(), rule.head, ruleContext);
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// Create new variable declarations for the head terms
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ruleContext.headVariablesStartIndex = ruleContext.freeVariables.size();
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ruleContext.freeVariables.reserve(ruleContext.headTerms.size());
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for (size_t i = 0; i < ruleContext.headTerms.size(); i++)
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{
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auto variableDeclaration = std::make_unique<ast::VariableDeclaration>(ast::VariableDeclaration::Type::Head);
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ruleContext.freeVariables.emplace_back(std::move(variableDeclaration));
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}
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ast::And antecedent;
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// Compute consequent
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auto headVariableIndex = ruleContext.headVariablesStartIndex;
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auto consequent = rule.head.data.accept(HeadLiteralTranslateToConsequentVisitor(), rule.head, ruleContext, context, headVariableIndex);
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assert(ruleContext.headTerms.size() == headVariableIndex - ruleContext.headVariablesStartIndex);
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if (!consequent)
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throw TranslationException(rule.head.location, "could not translate formula consequent");
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// Generate auxiliary variables replacing the head atom’s arguments
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for (auto i = ruleContext.headTerms.cbegin(); i != ruleContext.headTerms.cend(); i++)
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{
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const auto &headTerm = **i;
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const auto auxiliaryHeadVariableID = ruleContext.headVariablesStartIndex + i - ruleContext.headTerms.cbegin();
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auto element = ast::Variable(ruleContext.freeVariables[auxiliaryHeadVariableID].get());
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auto set = translate(headTerm, ruleContext, context, variableStack);
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auto in = ast::In(std::move(element), std::move(set));
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antecedent.arguments.emplace_back(std::move(in));
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}
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// Translate body literals
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for (auto i = rule.body.cbegin(); i != rule.body.cend(); i++)
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{
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const auto &bodyLiteral = *i;
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auto argument = bodyLiteral.data.accept(BodyBodyLiteralTranslateVisitor(), bodyLiteral, ruleContext, context, variableStack);
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if (!argument)
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throw TranslationException(bodyLiteral.location, "could not translate body literal");
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antecedent.arguments.emplace_back(std::move(argument.value()));
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}
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if (!ruleContext.isChoiceRule)
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{
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auto formula = ast::Formula::make<ast::Implies>(std::move(antecedent), std::move(consequent.value()));
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ast::ScopedFormula scopedFormula(std::move(formula), std::move(ruleContext.freeVariables));
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scopedFormulas.emplace_back(std::move(scopedFormula));
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reduce(scopedFormulas.back().formula.get<ast::Implies>());
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}
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else
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{
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const auto createFormula =
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[&](ast::Formula &argument, bool isLastOne)
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{
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auto &consequent = argument;
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if (!isLastOne)
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{
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auto formula = ast::Formula::make<ast::Implies>(ast::prepareCopy(antecedent), std::move(consequent));
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ast::ScopedFormula scopedFormula(std::move(formula), {});
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ast::fixDanglingVariables(scopedFormula);
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scopedFormulas.emplace_back(std::move(scopedFormula));
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}
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else
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{
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auto formula = ast::Formula::make<ast::Implies>(std::move(antecedent), std::move(consequent));
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ast::ScopedFormula scopedFormula(std::move(formula), std::move(ruleContext.freeVariables));
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scopedFormulas.emplace_back(std::move(scopedFormula));
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}
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auto &implies = scopedFormulas.back().formula.get<ast::Implies>();
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auto &antecedent = implies.antecedent.get<ast::And>();
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antecedent.arguments.emplace_back(ast::prepareCopy(implies.consequent));
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ast::fixDanglingVariables(scopedFormulas.back());
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reduce(implies);
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};
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if (consequent.value().is<ast::Or>())
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{
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auto &disjunction = consequent.value().get<ast::Or>();
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for (auto &argument : disjunction.arguments)
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createFormula(argument, &argument == &disjunction.arguments.back());
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}
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// TODO: check whether this is really correct for all possible consequent types
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else
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createFormula(consequent.value(), true);
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}
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}
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void visit(const Clingo::AST::ShowSignature &showSignature, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &, Context &context)
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{
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if (showSignature.csp)
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throw LogicException(statement.location, "CSP #show statements are not supported");
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auto &signature = showSignature.signature;
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if (signature.negative())
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throw LogicException(statement.location, "negative #show atom signatures are currently unsupported");
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context.showStatementsUsed = true;
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context.defaultPredicateVisibility = ast::PredicateDeclaration::Visibility::Hidden;
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if (std::strlen(signature.name()) == 0)
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{
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context.logger.log(output::Priority::Debug, statement.location) << "showing no predicates by default";
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return;
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}
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context.logger.log(output::Priority::Debug, statement.location) << "showing “" << signature.name() << "/" << signature.arity() << "”";
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auto predicateDeclaration = context.findOrCreatePredicateDeclaration(signature.name(), signature.arity());
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predicateDeclaration->visibility = ast::PredicateDeclaration::Visibility::Visible;
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}
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void visit(const Clingo::AST::ShowTerm &, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &, Context &)
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{
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throw LogicException(statement.location, "only #show statements for atoms (not terms) are supported currently");
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}
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void visit(const Clingo::AST::External &external, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &, Context &context)
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{
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const auto fail =
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[&]()
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{
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throw LogicException(statement.location, "only #external declarations of the form “#external <predicate name>(<arity>).” or “#external integer(<function name>(<arity>)).” supported");
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};
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if (!external.body.empty())
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fail();
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if (!external.atom.data.is<Clingo::AST::Function>())
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fail();
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const auto &predicate = external.atom.data.get<Clingo::AST::Function>();
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if (predicate.arguments.size() != 1)
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fail();
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const auto handleIntegerDeclaration =
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[&]()
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{
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// Integer function declarations are treated separately if applicable
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if (strcmp(predicate.name, "integer") != 0)
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return false;
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if (predicate.arguments.size() != 1)
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return false;
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const auto &functionArgument = predicate.arguments.front();
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if (!functionArgument.data.is<Clingo::AST::Function>())
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return false;
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const auto &function = functionArgument.data.get<Clingo::AST::Function>();
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if (function.arguments.size() != 1)
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return false;
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const auto &arityArgument = function.arguments.front();
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if (!arityArgument.data.is<Clingo::Symbol>())
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return false;
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const auto &aritySymbol = arityArgument.data.get<Clingo::Symbol>();
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if (aritySymbol.type() != Clingo::SymbolType::Number)
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return false;
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const size_t arity = aritySymbol.number();
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auto functionDeclaration = context.findOrCreateFunctionDeclaration(function.name, arity);
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functionDeclaration->domain = Domain::Integer;
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return true;
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};
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if (handleIntegerDeclaration())
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return;
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const auto &arityArgument = predicate.arguments.front();
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if (!arityArgument.data.is<Clingo::Symbol>())
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fail();
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const auto &aritySymbol = arityArgument.data.get<Clingo::Symbol>();
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if (aritySymbol.type() != Clingo::SymbolType::Number)
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fail();
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context.externalStatementsUsed = true;
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const size_t arity = aritySymbol.number();
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auto predicateDeclaration = context.findOrCreatePredicateDeclaration(predicate.name, arity);
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predicateDeclaration->isExternal = true;
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}
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template<class T>
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void visit(const T &, const Clingo::AST::Statement &statement, std::vector<ast::ScopedFormula> &, Context &)
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{
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throw LogicException(statement.location, "statement currently unsupported");
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}
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};
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////////////////////////////////////////////////////////////////////////////////////////////////////
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}
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#endif
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