diff --git a/src/ast.rs b/src/ast.rs
index 0b6c92e..dac7740 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -28,12 +28,14 @@ pub enum UnaryOperator
 
 // Primitives
 
+#[derive(Eq, Hash, PartialEq)]
 pub struct FunctionDeclaration
 {
 	pub name: String,
 	pub arity: usize,
 }
 
+#[derive(Eq, Hash, PartialEq)]
 pub struct PredicateDeclaration
 {
 	pub name: String,