From d056fabb8b8d5ed1abf8cdf7b316b34a5b16c41e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Patrick=20L=C3=BChne?= <patrick-github@luehne.de>
Date: Thu, 4 May 2017 15:44:37 +0200
Subject: [PATCH] Fixes lost signs with negated 0-ary predicates.

---
 CHANGELOG.md              |  4 ++++
 include/anthem/Body.h     | 11 +++++++++--
 tests/TestTranslation.cpp | 10 +++++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7e15001..30402e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## (unreleased)
 
+Bug Fixes:
+
+* fixes lost signs with negated 0-ary predicates
+
 ## 0.1.4 (2017-04-12)
 
 Features:
diff --git a/include/anthem/Body.h b/include/anthem/Body.h
index 0f93d1e..4e5bf4e 100644
--- a/include/anthem/Body.h
+++ b/include/anthem/Body.h
@@ -58,7 +58,14 @@ struct BodyTermTranslateVisitor
 			throwErrorAtLocation(literal.location, "double-negated literals currently unsupported", context);
 
 		if (function.arguments.empty())
-			return ast::Formula::make<ast::Predicate>(std::string(function.name));
+		{
+			auto predicate = ast::Formula::make<ast::Predicate>(std::string(function.name));
+
+			if (literal.sign == Clingo::AST::Sign::None)
+				return std::move(predicate);
+			else if (literal.sign == Clingo::AST::Sign::Negation)
+				return ast::Formula::make<ast::Not>(std::move(predicate));
+		}
 
 		std::vector<ast::Variable> variables;
 		variables.reserve(function.arguments.size());
@@ -82,7 +89,7 @@ struct BodyTermTranslateVisitor
 
 		if (literal.sign == Clingo::AST::Sign::None)
 			conjunction.arguments.emplace_back(std::move(predicate));
-		else
+		else if (literal.sign == Clingo::AST::Sign::Negation)
 			conjunction.arguments.emplace_back(ast::Formula::make<ast::Not>(std::move(predicate)));
 
 		context.auxiliaryBodyVariableID += function.arguments.size();
diff --git a/tests/TestTranslation.cpp b/tests/TestTranslation.cpp
index 1cd6fd5..b735d33 100644
--- a/tests/TestTranslation.cpp
+++ b/tests/TestTranslation.cpp
@@ -188,7 +188,15 @@ TEST_CASE("[translation] Rules are translated correctly", "[translation]")
 		CHECK(output.str() == "((V1 in M and V2 in N and V3 in O and V4 in P and exists X1, X2 (X1 in M and X2 in N and X1 < X2) and exists X3, X4 (X3 in P and X4 in O and X3 != X4)) -> p(V1, V2, V3, V4))\n");
 	}
 
-	SECTION("single negation")
+	SECTION("single negation with 0-ary predicates")
+	{
+		input << "not p :- not q.";
+		anthem::translate("input", input, context);
+
+		CHECK(output.str() == "(not q -> not p)\n");
+	}
+
+	SECTION("single negation with n-ary predicates")
 	{
 		input << "not p(X, 1) :- not q(X, 2).";
 		anthem::translate("input", input, context);