1 files changed, 8 insertions, 6 deletions
diff --git a/tuplr.hpp b/tuplr.hpp
index c86ff68..29b8463 100644
--- a/tuplr.hpp
+++ b/tuplr.hpp
@@ -99,13 +99,15 @@ struct CEnv; ///< Compile-Time Environment
 struct AST {
 	AST(Cursor c=Cursor()) : loc(c) {}
 	virtual ~AST() {}
-	virtual string str()                    const = 0;
-	virtual bool   operator==(const AST& o) const = 0;
-	virtual bool   contains(AST* child)     const { return false; }
-	virtual void   constrain(TEnv& tenv)    const {}
-	virtual void   lift(CEnv& cenv)               {}
-	virtual CValue compile(CEnv& cenv)            = 0;
+	virtual string str()                      const = 0;
+	virtual bool   operator==(const AST& o)   const = 0;
+	virtual bool   contains(const AST* child) const { return false; }
+	virtual void   constrain(TEnv& tenv)      const {}
+	virtual void   lift(CEnv& cenv)                 {}
 	Cursor loc;
+private:
+	friend class CEnv;
+	virtual CValue compile(CEnv& cenv)              = 0;
 };
 
 /// Literal value