diff --git a/src/format.rs b/src/format.rs
index 482ab16..1ce39bc 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -60,6 +60,38 @@ impl Precedence for crate::Formula
 	}
 }
 
+impl std::fmt::Debug for crate::FunctionDeclaration
+{
+	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(format, "{}/{}", &self.name, self.arity)
+	}
+}
+
+impl std::fmt::Display for crate::FunctionDeclaration
+{
+	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(format, "{:?}", &self)
+	}
+}
+
+impl std::fmt::Debug for crate::PredicateDeclaration
+{
+	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(format, "{}/{}", &self.name, self.arity)
+	}
+}
+
+impl std::fmt::Display for crate::PredicateDeclaration
+{
+	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result
+	{
+		write!(format, "{:?}", &self)
+	}
+}
+
 impl std::fmt::Debug for crate::VariableDeclaration
 {
 	fn fmt(&self, format: &mut std::fmt::Formatter) -> std::fmt::Result