From bdc560869a231cd79e7943898b0c85ec1fc5a74b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Patrick=20L=C3=BChne?= <patrick-github@luehne.de>
Date: Wed, 23 Nov 2016 03:47:32 +0100
Subject: [PATCH] Handling negated head literals.

---
 include/anthem/Head.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/anthem/Head.h b/include/anthem/Head.h
index ed27079..958c22d 100644
--- a/include/anthem/Head.h
+++ b/include/anthem/Head.h
@@ -215,6 +215,11 @@ struct HeadLiteralPrintSubstitutedVisitor
 {
 	void visit(const Clingo::AST::Literal &literal, const Clingo::AST::HeadLiteral &, const std::vector<const Clingo::AST::Term *> &terms)
 	{
+		if (literal.sign == Clingo::AST::Sign::DoubleNegation)
+			throwErrorAtLocation(literal.location, "double-negated literals currently unsupported");
+		else if (literal.sign == Clingo::AST::Sign::Negation)
+			std::cout << "not ";
+
 		literal.data.accept(LiteralPrintSubstitutedVisitor(), literal, terms);
 	}