diff --git a/src/anthem/Simplification.cpp b/src/anthem/Simplification.cpp index a7560fc..d7e8bd8 100644 --- a/src/anthem/Simplification.cpp +++ b/src/anthem/Simplification.cpp @@ -124,7 +124,7 @@ SimplificationResult simplify(ast::Formula &formula) //////////////////////////////////////////////////////////////////////////////////////////////////// -struct SimplificationRuleTrivialExists +struct SimplificationRuleTrivialAssignmentInExists { static constexpr const auto Description = "exists X (X = Y) === #true"; @@ -229,9 +229,53 @@ struct SimplificationRuleAssignmentInExists //////////////////////////////////////////////////////////////////////////////////////////////////// +struct SimplificationRuleEmptyConjunction +{ + static constexpr const auto Description = "[empty conjunction] === #true"; + + static SimplificationResult apply(ast::Formula &formula) + { + if (!formula.is()) + return SimplificationResult::Unchanged; + + auto &and_ = formula.get(); + + if (!and_.arguments.empty()) + return SimplificationResult::Unchanged; + + formula = ast::Formula::make(true); + + return SimplificationResult::Simplified; + } +}; + +//////////////////////////////////////////////////////////////////////////////////////////////////// + +struct SimplificationRuleTrivialExists +{ + static constexpr const auto Description = "exists ... ([#true/#false]) === [#true/#false]"; + + static SimplificationResult apply(ast::Formula &formula) + { + if (!formula.is()) + return SimplificationResult::Unchanged; + + auto &exists = formula.get(); + + if (!exists.argument.is()) + return SimplificationResult::Unchanged; + + formula = std::move(exists.argument); + + return SimplificationResult::Simplified; + } +}; + +//////////////////////////////////////////////////////////////////////////////////////////////////// + void simplify(ast::Exists &exists, ast::Formula &formula) { - SimplificationRuleTrivialExists::apply(formula); + SimplificationRuleTrivialAssignmentInExists::apply(formula); SimplificationRuleAssignmentInExists::apply(formula); if (!exists.argument.is()) @@ -240,13 +284,8 @@ void simplify(ast::Exists &exists, ast::Formula &formula) auto &and_ = exists.argument.get(); auto &arguments = and_.arguments; - // If there are no arguments left, we had a formula of the form “exists X1, ..., Xn (X1 = Y1 and ... and Xn = Yn)” - // Such exists statements are useless and can be safely replaced with “#true” - if (arguments.empty()) - { - formula = ast::Formula::make(true); - return; - } + SimplificationRuleEmptyConjunction::apply(exists.argument); + SimplificationRuleTrivialExists::apply(formula); // If the argument now is a conjunction with just one element, directly replace the input formula with the argument if (arguments.size() == 1)