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Move simplification rule to tableau

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This moves the rule “exists X (X = t and F(X)) === exists () (F(t))” to
the simplification rule tableau.
This commit is contained in:
Patrick Lühne 2018-03-25 19:14:04 +02:00
parent 5c5411c0ff
commit 7e3fc007c8
Signed by: patrick
GPG Key ID: 05F3611E97A70ABF
1 changed files with 71 additions and 45 deletions
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42
src/anthem/Simplification.cpp
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@ -161,19 +161,25 @@ struct SimplificationRuleTrivialExists
//////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////////////////////////////////
// Simplifies exists statements by using the equivalence “exists X (X = t and F(X))” == “F(t)” struct SimplificationRuleAssignmentInExists
// The exists statement has to be of the form “exists <variables> <conjunction>”
void simplify(ast::Exists &exists, ast::Formula &formula)
{ {
SimplificationRuleTrivialExists::apply(formula); static constexpr const auto Description = "exists X (X = t and F(X)) === exists () (F(t))";
static SimplificationResult apply(ast::Formula &formula)
{
if (!formula.is<ast::Exists>())
return SimplificationResult::Unchanged;
auto &exists = formula.get<ast::Exists>();
if (!exists.argument.is<ast::And>()) if (!exists.argument.is<ast::And>())
return; return SimplificationResult::Unchanged;
auto &conjunction = exists.argument.get<ast::And>(); auto &and_ = exists.argument.get<ast::And>();
auto &arguments = conjunction.arguments; auto &arguments = and_.arguments;
auto simplificationResult = SimplificationResult::Unchanged;
// Simplify formulas of type “exists X (X = t and F(X))” to “F(t)”
for (auto i = exists.variables.begin(); i != exists.variables.end();) for (auto i = exists.variables.begin(); i != exists.variables.end();)
{ {
const auto &variableDeclaration = **i; const auto &variableDeclaration = **i;
@ -201,7 +207,10 @@ void simplify(ast::Exists &exists, ast::Formula &formula)
} }
arguments.erase(j); arguments.erase(j);
wasVariableReplaced = true; wasVariableReplaced = true;
simplificationResult = SimplificationResult::Simplified;
break; break;
} }
@ -214,6 +223,23 @@ void simplify(ast::Exists &exists, ast::Formula &formula)
i++; i++;
} }
return simplificationResult;
}
};
////////////////////////////////////////////////////////////////////////////////////////////////////
void simplify(ast::Exists &exists, ast::Formula &formula)
{
SimplificationRuleTrivialExists::apply(formula);
SimplificationRuleAssignmentInExists::apply(formula);
if (!exists.argument.is<ast::And>())
return;
auto &and_ = exists.argument.get<ast::And>();
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)” // 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” // Such exists statements are useless and can be safely replaced with “#true”
if (arguments.empty()) if (arguments.empty())