diff --git a/src/bytecode.rs b/src/bytecode.rs
index 80d37b0..73ec019 100644
--- a/src/bytecode.rs
+++ b/src/bytecode.rs
@@ -49,8 +49,6 @@ pub enum OpCode {
 
     /// push an empty attribute set onto stack
     AttrSet,
-    /// push an empty recursive attribute set onto stack
-    RecAttrSet,
     /// [ .. set value ] consume 1 element, push a static kv pair (`name`, `value`) into `set`
     PushStaticAttr { name: EcoString },
     /// [ .. set name value ] consume 2 elements, push a dynamic kv pair (`name`, `value`) in to `set`
diff --git a/src/ty/internal/func.rs b/src/ty/internal/func.rs
index d87e5a2..6e904f1 100644
--- a/src/ty/internal/func.rs
+++ b/src/ty/internal/func.rs
@@ -1,5 +1,6 @@
 use ecow::EcoString;
 
+use crate::ty::internal::Value;
 use crate::bytecode::{OpCodes, ThunkIdx};
 
 #[derive(Debug, Clone)]
@@ -18,6 +19,12 @@ pub struct Func {
     pub opcodes: OpCodes
 }
 
+impl Func {
+    pub fn call(self, _arg: Value) -> Value {
+        todo!()
+    }
+}
+
 impl PartialEq for Func {
     fn eq(&self, _: &Self) -> bool {
         false
diff --git a/src/ty/internal/mod.rs b/src/ty/internal/mod.rs
index b27c181..fa2ec2f 100644
--- a/src/ty/internal/mod.rs
+++ b/src/ty/internal/mod.rs
@@ -43,10 +43,31 @@ pub enum Value {
 
 use Value::Const as VmConst;
 impl Value {
-    pub fn call(self, args: Vec<Value>) -> Value {
+    pub fn callable(&self) -> bool {
         match self {
-            Value::PrimOp(func) => func.call(args),
-            Value::PartialPrimOp(func) => func.call(args),
+            Value::PrimOp(_) | Value::PartialPrimOp(_) | Value::Const(Const::Func(_)) => true,
+            Value::AttrSet(_) => todo!(),
+            _ => false,
+        }
+    }
+
+    pub fn call(self, args: Vec<Value>) -> Value {
+        use Value as V;
+        match self {
+            V::PrimOp(func) => func.call(args),
+            V::PartialPrimOp(func) => func.call(args),
+            mut func @ Value::Const(Const::Func(_)) => {
+                let mut iter = args.into_iter();
+                while let Some(arg) = iter.next() {
+                    func = match func {
+                        V::PrimOp(func) => return func.call([arg].into_iter().chain(iter).collect()),
+                        V::PartialPrimOp(func) => return func.call([arg].into_iter().chain(iter).collect()),
+                        V::Const(Const::Func(func)) => func.call(arg),
+                        _ => todo!()
+                    }
+                }
+                func
+            }
             _ => todo!(),
         }
     }
diff --git a/src/vm/vm.rs b/src/vm/vm.rs
index eccef44..fb4c34c 100644
--- a/src/vm/vm.rs
+++ b/src/vm/vm.rs
@@ -81,6 +81,12 @@ impl VM {
                 let func = stack.pop()?;
                 stack.push(func.call(args))?;
             }
+            OpCode::Func { param, length } => {
+                todo!()
+            }
+            OpCode::Ret => {
+                todo!()
+            }
             OpCode::UnOp { op } => {
                 use UnOp::*;
                 let value = stack.pop()?;
@@ -105,6 +111,9 @@ impl VM {
                 let rhs = stack.pop()?;
                 stack.tos_mut()?.concat_string(rhs);
             }
+            OpCode::Path => {
+                todo!()
+            }
             OpCode::List => {
                 stack.push(Value::List(List::empty()))?;
             }
@@ -166,7 +175,11 @@ impl VM {
             OpCode::LeaveEnv => {
                 env.leave();
             }
-            _ => todo!(),
+            OpCode::Assert => {
+                if !stack.pop()?.unwrap_const().unwrap_bool() {
+                    todo!()
+                }
+            }
         }
         Ok(0)
     }