DEV: The beginnings of a runtime for the opcode vm.

src/build/mod.rs

@@ -102,6 +102,31 @@ pub struct AssertCollector {
     pub failures: String,
 }
 
+impl AssertCollector {
+    pub fn new() -> Self {
+        Self {
+            counter: 0,
+            success: true,
+            summary: String::new(),
+            failures: String::new(),
+        }
+    }
+    
+    fn record_assert_result(&mut self, msg: &str, is_success: bool) {
+        if !is_success {
+            let msg = format!("{} - NOT OK: {}\n", self.counter, msg);
+            self.summary.push_str(&msg);
+            self.failures.push_str(&msg);
+            self.success = false;
+        } else {
+            let msg = format!("{} - OK: {}\n", self.counter, msg);
+            self.summary.push_str(&msg);
+        }
+        self.counter += 1;
+    }
+
+}
+
 /// Builder handles building ucg code for a single file.
 pub struct FileBuilder<'a, C>
 where
@@ -169,12 +194,7 @@ where
             std: Rc::new(stdlib::get_libs()),
             import_path: import_paths,
             validate_mode: false,
-            assert_collector: AssertCollector {
+            assert_collector: AssertCollector::new(),
-                counter: 0,
-                success: true,
-                summary: String::new(),
-                failures: String::new(),
-            },
             scope: scope,
             import_registry: ImporterRegistry::make_registry(),
             converter_registry: converter_registry,
@@ -1686,19 +1706,6 @@ where
         };
     }
 
-    fn record_assert_result(&mut self, msg: &str, is_success: bool) {
-        if !is_success {
-            let msg = format!("{} - NOT OK: {}\n", self.assert_collector.counter, msg);
-            self.assert_collector.summary.push_str(&msg);
-            self.assert_collector.failures.push_str(&msg);
-            self.assert_collector.success = false;
-        } else {
-            let msg = format!("{} - OK: {}\n", self.assert_collector.counter, msg);
-            self.assert_collector.summary.push_str(&msg);
-        }
-        self.assert_collector.counter += 1;
-    }
-
     fn eval_assert(&mut self, expr: &Expression, scope: &Scope) -> Result<Rc<Val>, Box<dyn Error>> {
         if !self.validate_mode {
             // we are not in validate_mode so build_asserts are noops.
@@ -1715,7 +1722,7 @@ where
             Err(e) => {
                 // failure!
                 let msg = format!("CompileError: {}\nfor expression:\n{}\n", e, expr_pretty);
-                self.record_assert_result(&msg, false);
+                self.assert_collector.record_assert_result(&msg, false);
                 return Ok(Rc::new(Val::Empty));
             }
         };
@@ -1730,7 +1737,7 @@ where
                                     "TYPE FAIL - Expected Boolean field ok in tuple {}, line: {}, column: {}",
                                     ok.as_ref(), expr.pos().line, expr.pos().column
                                 );
-                            self.record_assert_result(&msg, false);
+                            self.assert_collector.record_assert_result(&msg, false);
                             return Ok(Rc::new(Val::Empty));
                         }
                     },
@@ -1739,7 +1746,7 @@ where
                             "TYPE FAIL - Expected Boolean field ok in tuple {}, line: {}, column: {}",
                             ok.as_ref(), expr.pos().line, expr.pos().column
                         );
-                        self.record_assert_result(&msg, false);
+                        self.assert_collector.record_assert_result(&msg, false);
                         return Ok(Rc::new(Val::Empty));
                     }
                 };
@@ -1751,7 +1758,7 @@ where
                                     "TYPE FAIL - Expected String field desc in tuple {} line: {}, column: {}",
                                     ok, expr.pos().line, expr.pos().column
                                 );
-                            self.record_assert_result(&msg, false);
+                            self.assert_collector.record_assert_result(&msg, false);
                             return Ok(Rc::new(Val::Empty));
                         }
                     },
@@ -1760,11 +1767,11 @@ where
                             "TYPE FAIL - Expected String field desc in tuple {} line: {}, column: {}\n",
                             ok, expr.pos().line, expr.pos().column
                         );
-                        self.record_assert_result(&msg, false);
+                        self.assert_collector.record_assert_result(&msg, false);
                         return Ok(Rc::new(Val::Empty));
                     }
                 };
-                self.record_assert_result(&desc, ok_field);
+                self.assert_collector.record_assert_result(&desc, ok_field);
             }
             &Val::Empty
             | &Val::Boolean(_)
@@ -1780,7 +1787,7 @@ where
                     "TYPE FAIL - Expected tuple with ok and desc fields got {} at line: {} column: {}\n",
                     ok, expr.pos().line, expr.pos().column
                 );
-                self.record_assert_result(&msg, false);
+                self.assert_collector.record_assert_result(&msg, false);
                 return Ok(Rc::new(Val::Empty));
             }
         }

src/build/opcode/cache.rs

@@ -0,0 +1,44 @@
+// Copyright 2019 Jeremy Wall
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+use std::collections::btree_map;
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+use super::{Op, OpPointer};
+
+/// A Cache of Op codes.
+pub struct Ops {
+    ops: BTreeMap<String, Rc<Vec<Op>>>,
+}
+
+impl Ops {
+    pub fn new() -> Self {
+        Self {
+            ops: BTreeMap::new(),
+        }
+    }
+
+    pub fn entry<'a, S: Into<String>>(&'a mut self, path: S) -> Entry<'a> {
+        Entry(self.ops.entry(path.into()))
+    }
+}
+
+pub struct Entry<'a>(btree_map::Entry<'a, String, Rc<Vec<Op>>>);
+
+impl<'a> Entry<'a> {
+    pub fn get_pointer_or_else<F: FnOnce() -> Vec<Op>>(self, f: F) -> OpPointer {
+        let cached = self.0.or_insert_with(|| Rc::new(f())).clone();
+        OpPointer::new(cached)
+    }
+}

src/build/opcode/mod.rs

@@ -11,7 +11,11 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+use std::rc::Rc;
+
+mod cache;
 pub mod pointer;
+mod runtime;
 pub mod scope;
 mod vm;
 
@@ -32,8 +36,8 @@ pub enum Primitive {
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum Composite {
-    List(Vec<Value>),
+    List(Vec<Rc<Value>>),
-    Tuple(Vec<(String, Value)>),
+    Tuple(Vec<(String, Rc<Value>)>),
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -47,7 +51,7 @@ pub struct Func {
 pub struct Module {
     ptr: OpPointer,
     result_ptr: Option<usize>,
-    flds: Vec<(String, Value)>,
+    flds: Vec<(String, Rc<Value>)>,
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -66,6 +70,18 @@ pub enum Value {
     M(Module),
 }
 
+#[derive(Debug, PartialEq, Clone)]
+pub enum Hook {
+    Map,
+    Include,
+    Filter,
+    Reduce,
+    Import,
+    Out,
+    Assert,
+    Convert,
+}
+
 #[derive(Debug, PartialEq, Clone)]
 pub enum Op {
     // Stack and Name manipulation.
@@ -115,13 +131,7 @@ pub enum Op {
     // Calls
     FCall,
     // Runtime hooks
-    // - Map,
+    Runtime(Hook),
-    // - Filter,
-    // - Reduce,
-    // - Import,
-    // - Out,
-    // - Assert,
-    // - Convert,
 }
 
 #[derive(Debug)]

src/build/opcode/runtime.rs

@@ -0,0 +1,156 @@
+// Copyright 2019 Jeremy Wall
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+use super::cache;
+use super::VM;
+use super::{Composite, Error, Hook, Primitive, Value};
+use crate::build::AssertCollector;
+use Composite::Tuple;
+use Primitive::{Bool, Str};
+
+pub struct Builtins {
+    op_cache: cache::Ops,
+    val_cache: BTreeMap<String, Rc<Value>>,
+    assert_results: AssertCollector,
+    // TODO(jwall): IO sink for stderr
+    // TODO(jwall): IO sink for stdout
+}
+
+impl Builtins {
+    pub fn new() -> Self {
+        Self {
+            op_cache: cache::Ops::new(),
+            val_cache: BTreeMap::new(),
+            assert_results: AssertCollector::new(),
+        }
+    }
+
+    pub fn handle(&mut self, h: Hook, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        match h {
+            Hook::Import => self.import(stack),
+            Hook::Include => self.include(stack),
+            Hook::Assert => self.assert(stack),
+            Hook::Convert => self.convert(stack),
+            Hook::Out => self.out(stack),
+            Hook::Map => self.map(stack),
+            Hook::Filter => self.filter(stack),
+            Hook::Reduce => self.reduce(stack),
+        }
+    }
+
+    fn import(&mut self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        let path = stack.pop();
+        if let Some(val) = path {
+            if let &Value::P(Str(ref path)) = val.as_ref() {
+                if self.val_cache.contains_key(path) {
+                    stack.push(self.val_cache[path].clone());
+                } else {
+                    let op_pointer = self.op_cache.entry(path).get_pointer_or_else(|| {
+                        // TODO(jwall): import
+                        unimplemented!("Compiling paths are not implemented yet");
+                    });
+                    let mut vm = VM::with_pointer(op_pointer);
+                    vm.run()?;
+                    let result = Rc::new(vm.symbols_to_tuple(true));
+                    self.val_cache.insert(path.clone(), result.clone());
+                    stack.push(result);
+                }
+                return Ok(());
+            }
+        }
+        return Err(Error {});
+    }
+
+    fn include(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): include
+        let path = stack.pop();
+        if let Some(val) = path {
+            if let &Value::P(Str(ref path)) = val.as_ref() {}
+            unimplemented!("TODO(jwall): Includes are not implemented yet")
+        }
+        return Err(Error {});
+    }
+
+    fn assert(&mut self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): assert
+        let tuple = stack.pop();
+        if let Some(val) = tuple.clone() {
+            if let &Value::C(Tuple(ref tuple)) = val.as_ref() {
+                // look for the description field
+                let mut desc = None;
+                // look for the ok field.
+                let mut ok = None;
+                for &(ref name, ref val) in tuple.iter() {
+                    if name == "description" {
+                        desc = Some(val.clone());
+                    }
+                    if name == "ok" {
+                        ok = Some(val.clone());
+                    }
+                }
+                if let (Some(ok), Some(desc)) = (ok, desc) {
+                    if let (&Value::P(Bool(ref b)), &Value::P(Str(ref desc))) =
+                        (ok.as_ref(), desc.as_ref())
+                    {
+                        self.assert_results.record_assert_result(desc, *b);
+                        return Ok(());
+                    }
+                }
+            }
+        }
+        let msg = format!(
+            "TYPE FAIL - Expected tuple with ok and desc fields got {:?} at line: {} column: {}\n",
+            tuple, "TODO", "TODO"
+        );
+        self.assert_results.record_assert_result(&msg, false);
+        return Ok(());
+    }
+
+    fn convert(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): convert
+        let val = stack.pop();
+        if let Some(val) = val {
+            unimplemented!("TODO(jwall): Conversions are not implemented yet")
+        } else {
+            Err(Error {})
+        }
+    }
+
+    fn out(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): out
+        let val = stack.pop();
+        if let Some(val) = val {
+            unimplemented!("TODO(jwall): Out expressions are not implemented yet")
+        } else {
+            Err(Error {})
+        }
+    }
+
+    fn map(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): map (combine these into one?)
+        unimplemented!("TODO(jwall): Map expressions are not implemented yet")
+    }
+
+    fn filter(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): filter
+        unimplemented!("TODO(jwall): Filter expressions are not implemented yet")
+    }
+
+    fn reduce(&self, stack: &mut Vec<Rc<Value>>) -> Result<(), Error> {
+        // TODO(jwall): reduce
+        unimplemented!("TODO(jwall): Reduce expressions are not implemented yet")
+    }
+}

src/build/opcode/scope.rs

@@ -13,13 +13,14 @@
 // limitations under the License.
 use std::collections::{BTreeMap, BTreeSet};
 use std::iter::FromIterator;
+use std::rc::Rc;
 
 use super::{Error, Value};
 
 #[derive(Clone, PartialEq, Debug)]
 pub enum Bindings {
-    Sealed(BTreeMap<String, Value>),
+    Sealed(BTreeMap<String, Rc<Value>>),
-    Open(BTreeMap<String, Value>),
+    Open(BTreeMap<String, Rc<Value>>),
 }
 use Bindings::{Open, Sealed};
 
@@ -42,14 +43,14 @@ impl Bindings {
         }
     }
 
-    pub fn get(&self, name: &str) -> Option<&Value> {
+    pub fn get(&self, name: &str) -> Option<Rc<Value>> {
         match self {
-            Open(flds) => flds.get(name),
+            Open(flds) => flds.get(name).cloned(),
-            Sealed(flds) => flds.get(name),
+            Sealed(flds) => flds.get(name).cloned(),
         }
     }
 
-    pub fn add(&mut self, name: String, val: Value) {
+    pub fn add(&mut self, name: String, val: Rc<Value>) {
         match self {
             Sealed(flds) => flds.insert(name, val),
             Open(flds) => flds.insert(name, val),
@@ -78,26 +79,17 @@ impl Stack {
         }
     }
 
-    pub fn get(&self, name: &str) -> Option<&Value> {
+    pub fn get(&self, name: &str) -> Option<Rc<Value>> {
         match &self.curr {
-            Sealed(flds) => flds.get(name),
+            Sealed(flds) => flds.get(name).cloned(),
             Open(flds) => {
                 if let Some(v) = flds.get(name) {
-                    return Some(v);
+                    return Some(v.clone());
                 } else {
                     for b in self.prev.iter() {
                         match b {
-                            Sealed(bflds) => {
+                            Sealed(bflds) => return bflds.get(name).cloned(),
-                                if let Some(v) = bflds.get(name) {
+                            Open(bflds) => return bflds.get(name).cloned(),
-                                    return Some(v);
-                                }
-                                return None;
-                            }
-                            Open(bflds) => {
-                                if let Some(v) = bflds.get(name) {
-                                    return Some(v);
-                                }
-                            }
                         }
                     }
                 }
@@ -132,7 +124,7 @@ impl Stack {
         }
     }
 
-    pub fn add(&mut self, name: String, val: Value) {
+    pub fn add(&mut self, name: String, val: Rc<Value>) {
         self.curr.add(name, val);
     }
 

src/build/opcode/test.rs

@@ -29,7 +29,7 @@ macro_rules! assert_cases {
         for case in $cases.drain(0..) {
             let mut vm = VM::new(Rc::new(case.0));
             vm.run().unwrap();
-            assert_eq!(dbg!(vm.pop()).unwrap(), case.1);
+            assert_eq!(dbg!(vm.pop()).unwrap(), Rc::new(case.1));
         }
     };
 
@@ -92,7 +92,7 @@ fn test_bind_op() {
         vm.run().unwrap();
         let (name, result) = case.1;
         let v = vm.get_binding(name).unwrap();
-        assert_eq!(&result, v);
+        assert_eq!(&result, v.as_ref());
     }
 }
 
@@ -100,8 +100,8 @@ fn test_bind_op() {
 fn test_list_ops() {
     assert_cases!(
         vec![InitList] => C(List(Vec::new())),
-        vec![InitList, Val(Int(1)), Element] => C(List(vec![P(Int(1))])),
+        vec![InitList, Val(Int(1)), Element] => C(List(vec![Rc::new(P(Int(1)))])),
-        vec![InitList, Val(Int(2)), Element, Val(Int(1)), Element] => C(List(vec![P(Int(2)), P(Int(1))])),
+        vec![InitList, Val(Int(2)), Element, Val(Int(1)), Element] => C(List(vec![Rc::new(P(Int(2))), Rc::new(P(Int(1)))])),
         vec![
             InitList,
             Val(Int(1)),
@@ -110,7 +110,7 @@ fn test_list_ops() {
             Val(Int(1)),
             Add,
             Element,
-        ] => C(List(vec![P(Int(1)), P(Int(2))])),
+        ] => C(List(vec![Rc::new(P(Int(1))), Rc::new(P(Int(2)))])),
     );
 }
 
@@ -118,7 +118,14 @@ fn test_list_ops() {
 fn test_tuple_ops() {
     assert_cases!(
         vec![InitTuple] => C(Tuple(Vec::new())),
-        vec![InitTuple, Val(Str("foo".to_owned())), Val(Int(1)), Field] => C(Tuple(vec![("foo".to_owned(), P(Int(1)))])),
+        vec![
+            InitTuple,
+            Val(Str("foo".to_owned())),
+            Val(Int(1)),
+            Field,
+        ] => C(Tuple(vec![
+            ("foo".to_owned(), Rc::new(P(Int(1)))),
+        ])),
         vec![
             InitTuple,
             Sym("bar".to_owned()),
@@ -128,8 +135,8 @@ fn test_tuple_ops() {
             Val(Int(1)),
             Field,
         ] => C(Tuple(vec![
-            ("bar".to_owned(), P(Str("quux".to_owned()))),
+            ("bar".to_owned(), Rc::new(P(Str("quux".to_owned())))),
-            ("foo".to_owned(), P(Int(1))),
+            ("foo".to_owned(), Rc::new(P(Int(1)))),
         ])),
         vec![
             InitTuple,
@@ -143,8 +150,8 @@ fn test_tuple_ops() {
             Val(Int(2)),
             Field,
         ] => C(Tuple(vec![
-            ("bar".to_owned(), P(Str("quux".to_owned()))),
+            ("bar".to_owned(), Rc::new(P(Str("quux".to_owned())))),
-            ("foo".to_owned(), P(Int(2))),
+            ("foo".to_owned(), Rc::new(P(Int(2)))),
         ])),
         vec![
             InitTuple,
@@ -160,8 +167,8 @@ fn test_tuple_ops() {
             Val(Int(2)),
             Field,
         ] => C(Tuple(vec![
-            ("bar".to_owned(), P(Str("quux".to_owned()))),
+            ("bar".to_owned(), Rc::new(P(Str("quux".to_owned())))),
-            ("foo".to_owned(), P(Int(2))),
+            ("foo".to_owned(), Rc::new(P(Int(2)))),
         ])),
         vec![
             InitTuple, // Override tuple
@@ -179,8 +186,8 @@ fn test_tuple_ops() {
             Field,
             Cp, // Do the tuple copy operation
         ] => C(Tuple(vec![
-            ("bar".to_owned(), P(Str("quux".to_owned()))),
+            ("bar".to_owned(), Rc::new(P(Str("quux".to_owned())))),
-            ("foo".to_owned(), P(Int(2))),
+            ("foo".to_owned(), Rc::new(P(Int(2)))),
         ])),
     );
 }
@@ -368,10 +375,10 @@ fn test_module_call() {
         ] => C(Tuple(vec![
             (
                 "foo".to_owned(),
-                C(Tuple(vec![
+                Rc::new(C(Tuple(vec![
-                    ("one".to_owned(), P(Int(11))),
+                    ("one".to_owned(), Rc::new(P(Int(11)))),
-                    ("two".to_owned(), P(Int(2))),
+                    ("two".to_owned(), Rc::new(P(Int(2)))),
-                ]))
+                ])))
             ),
         ])),
         vec![
@@ -486,12 +493,12 @@ fn test_index_operation() {
 #[test]
 fn test_scope_stacks() {
     let mut stack = Stack::new();
-    stack.add("one".to_owned(), P(Int(1)));
+    stack.add("one".to_owned(), Rc::new(P(Int(1))));
     let mut val = stack.get("one").unwrap();
-    assert_eq!(val, &P(Int(1)));
+    assert_eq!(val.as_ref(), &P(Int(1)));
     stack.push();
     assert!(stack.get("one").is_none());
     stack.to_open();
     val = stack.get("one").unwrap();
-    assert_eq!(val, &P(Int(1)));
+    assert_eq!(val.as_ref(), &P(Int(1)));
 }

src/build/opcode/vm.rs

@@ -1,30 +1,34 @@
 // Copyright 2019 Jeremy Wall
-// 
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
-// 
+//
 //     http://www.apache.org/licenses/LICENSE-2.0
-// 
+//
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+use std::cell::RefCell;
 use std::rc::Rc;
 
-use super::{Value, Op, Primitive, Error};
-use super::scope::{Stack};
 use super::pointer::OpPointer;
+use super::runtime;
+use super::scope::Stack;
+use super::{Error, Op, Primitive, Value};
 
-use super::Value::{C, F, M, T, S, P};
-use super::Primitive::{Int, Str, Float, Bool};
 use super::Composite::{List, Tuple};
+use super::Hook;
+use super::Primitive::{Bool, Float, Int, Str};
+use super::Value::{C, F, M, P, S, T};
 use super::{Func, Module};
 
 pub struct VM {
-    stack: Vec<Value>,
+    stack: Vec<Rc<Value>>,
     symbols: Stack,
+    runtime: Rc<RefCell<runtime::Builtins>>,
     ops: OpPointer,
 }
 
@@ -37,6 +41,7 @@ impl<'a> VM {
         Self {
             stack: Vec::new(),
             symbols: Stack::new(),
+            runtime: Rc::new(RefCell::new(runtime::Builtins::new())),
             ops: ops,
         }
     }
@@ -45,10 +50,21 @@ impl<'a> VM {
         Self {
             stack: Vec::new(),
             symbols: symbols,
+            runtime: self.runtime.clone(),
             ops: self.ops.clone(),
         }
     }
 
+    pub fn symbols_to_tuple(&self, include_mod: bool) -> Value {
+        let mut flds = Vec::new();
+        for sym in self.symbols.symbol_list() {
+            if include_mod || sym != "mod" {
+                flds.push((sym.clone(), self.symbols.get(sym).unwrap().clone()));
+            }
+        }
+        return C(Tuple(flds));
+    }
+
     pub fn run(&mut self) -> Result<(), Error> {
         loop {
             let op = if let Some(op) = dbg!(self.ops.next()) {
@@ -58,8 +74,8 @@ impl<'a> VM {
             };
             let idx = self.ops.idx()?;
             match op {
-                Op::Val(p) => self.push(dbg!(P(p.clone())))?,
+                Op::Val(p) => self.push(Rc::new(dbg!(P(p.clone()))))?,
-                Op::Sym(s) => self.push(dbg!(S(s.clone())))?,
+                Op::Sym(s) => self.push(Rc::new(dbg!(S(s.clone()))))?,
                 Op::DeRef(s) => self.op_deref(s.clone())?,
                 Op::Add => self.op_add()?,
                 Op::Sub => self.op_sub()?,
@@ -72,9 +88,9 @@ impl<'a> VM {
                 Op::GtEq => self.op_gteq()?,
                 Op::LtEq => self.op_lteq()?,
                 // Add a Composite list value to the stack
-                Op::InitList => self.push(C(List(Vec::new())))?,
+                Op::InitList => self.push(Rc::new(C(List(Vec::new()))))?,
                 // Add a composite tuple value to the stack
-                Op::InitTuple => self.push(C(Tuple(Vec::new())))?,
+                Op::InitTuple => self.push(Rc::new(C(Tuple(Vec::new()))))?,
                 Op::Field => self.op_field()?,
                 Op::Element => self.op_element()?,
                 Op::Index => self.op_index()?,
@@ -96,6 +112,7 @@ impl<'a> VM {
                 Op::Pop => {
                     self.pop()?;
                 }
+                Op::Runtime(h) => self.op_runtime(h)?,
             };
         }
         Ok(())
@@ -117,7 +134,8 @@ impl<'a> VM {
     }
 
     fn op_jump_if_true(&mut self, jp: i32) -> Result<(), Error> {
-        if let P(Bool(cond)) = self.pop()? {
+        let cond = self.pop()?;
+        if let &P(Bool(cond)) = cond.as_ref() {
             if cond {
                 self.op_jump(jp)?;
             }
@@ -126,7 +144,8 @@ impl<'a> VM {
     }
 
     fn op_jump_if_false(&mut self, jp: i32) -> Result<(), Error> {
-        if let P(Bool(cond)) = self.pop()? {
+        let cond = self.pop()?;
+        if let &P(Bool(cond)) = cond.as_ref() {
             if !cond {
                 self.op_jump(jp)?;
             }
@@ -150,11 +169,13 @@ impl<'a> VM {
     }
 
     fn op_module(&'a mut self, idx: usize, jptr: usize) -> Result<(), Error> {
-        let (result_ptr, flds) = match self.pop()? {
+        let mod_val = self.pop()?;
-            C(Tuple(flds)) => (None, flds),
+        let (result_ptr, flds) = match mod_val.as_ref() {
-            T(ptr) => {
+            &C(Tuple(ref flds)) => (None, flds.clone()),
-                if let C(Tuple(flds)) = self.pop()? {
+            &T(ptr) => {
-                    (Some(ptr), flds)
+                let tpl_val = self.pop()?;
+                if let &C(Tuple(ref flds)) = tpl_val.as_ref() {
+                    (Some(ptr), flds.clone())
                 } else {
                     return dbg!(Err(Error {}));
                 }
@@ -165,11 +186,11 @@ impl<'a> VM {
         };
         let mut ops = self.ops.clone();
         ops.jump(idx)?;
-        self.push(M(Module {
+        self.push(Rc::new(M(Module {
             ptr: dbg!(ops),
             result_ptr: result_ptr,
             flds: dbg!(flds),
-        }))?;
+        })))?;
         self.ops.jump(dbg!(jptr))
     }
 
@@ -181,10 +202,11 @@ impl<'a> VM {
         eprintln!("Defining a new function");
         let mut bindings = Vec::new();
         // get imported symbols from stack
-        if let C(List(elems)) = self.pop()? {
+        let list_val = self.pop()?;
+        if let &C(List(ref elems)) = list_val.as_ref() {
             for e in elems {
-                if let S(sym) = e {
+                if let &S(ref sym) = e.as_ref() {
-                    bindings.push(sym);
+                    bindings.push(sym.clone());
                 } else {
                     return dbg!(Err(Error {}));
                 }
@@ -195,29 +217,29 @@ impl<'a> VM {
         eprintln!("Pushing function definition on stack");
         let mut ops = self.ops.clone();
         ops.jump(idx)?;
-        self.push(dbg!(F(Func {
+        self.push(Rc::new(dbg!(F(Func {
             ptr: ops, // where the function starts.
             bindings: bindings,
             snapshot: scope_snapshot,
-        })))?;
+        }))))?;
         eprintln!("Jumping to {} past the function body", jptr);
         self.ops.jump(jptr)
     }
 
     fn op_fcall(&mut self) -> Result<(), Error> {
         let f = self.pop()?;
-        if let F(Func {
+        if let &F(Func {
-            ptr,
+            ref ptr,
-            bindings,
+            ref bindings,
-            snapshot,
+            ref snapshot,
-        }) = f
+        }) = f.as_ref()
         {
             // use the captured scope snapshot for the function.
-            let mut vm = Self::with_pointer(ptr).to_scoped(snapshot);
+            let mut vm = Self::with_pointer(ptr.clone()).to_scoped(snapshot.clone());
-            for nm in bindings {
+            for nm in bindings.iter() {
                 // now put each argument on our scope stack as a binding.
                 let val = self.pop()?;
-                vm.binding_push(nm, val)?;
+                vm.binding_push(nm.clone(), val)?;
             }
             // proceed to the function body
             vm.run()?;
@@ -229,26 +251,26 @@ impl<'a> VM {
     }
 
     fn op_thunk(&mut self, idx: usize, jp: i32) -> Result<(), Error> {
-        self.push(dbg!(T(idx)))?;
+        self.push(Rc::new(dbg!(T(idx))))?;
         self.op_jump(jp)
     }
 
     fn op_equal(&mut self) -> Result<(), Error> {
         let left = self.pop()?;
         let right = self.pop()?;
-        self.push(P(Bool(left == right)))?;
+        self.push(Rc::new(P(Bool(left == right))))?;
         Ok(())
     }
 
     fn op_gt(&mut self) -> Result<(), Error> {
         let left = self.pop()?;
         let right = self.pop()?;
-        match (left, right) {
+        match (left.as_ref(), right.as_ref()) {
-            (P(Int(i)), P(Int(ii))) => {
+            (&P(Int(i)), &P(Int(ii))) => {
-                self.push(P(Bool(i > ii)))?;
+                self.push(Rc::new(P(Bool(i > ii))))?;
             }
-            (P(Float(f)), P(Float(ff))) => {
+            (&P(Float(f)), &P(Float(ff))) => {
-                self.push(P(Bool(f > ff)))?;
+                self.push(Rc::new(P(Bool(f > ff))))?;
             }
             _ => return Err(Error {}),
         }
@@ -258,12 +280,12 @@ impl<'a> VM {
     fn op_lt(&mut self) -> Result<(), Error> {
         let left = self.pop()?;
         let right = self.pop()?;
-        match (left, right) {
+        match (left.as_ref(), right.as_ref()) {
-            (P(Int(i)), P(Int(ii))) => {
+            (&P(Int(i)), &P(Int(ii))) => {
-                self.push(P(Bool(i < ii)))?;
+                self.push(Rc::new(P(Bool(i < ii))))?;
             }
-            (P(Float(f)), P(Float(ff))) => {
+            (&P(Float(f)), &P(Float(ff))) => {
-                self.push(P(Bool(f < ff)))?;
+                self.push(Rc::new(P(Bool(f < ff))))?;
             }
             _ => return Err(Error {}),
         }
@@ -273,12 +295,12 @@ impl<'a> VM {
     fn op_lteq(&mut self) -> Result<(), Error> {
         let left = self.pop()?;
         let right = self.pop()?;
-        match (left, right) {
+        match (left.as_ref(), right.as_ref()) {
-            (P(Int(i)), P(Int(ii))) => {
+            (&P(Int(i)), &P(Int(ii))) => {
-                self.push(P(Bool(i <= ii)))?;
+                self.push(Rc::new(P(Bool(i <= ii))))?;
             }
-            (P(Float(f)), P(Float(ff))) => {
+            (&P(Float(f)), &P(Float(ff))) => {
-                self.push(P(Bool(f <= ff)))?;
+                self.push(Rc::new(P(Bool(f <= ff))))?;
             }
             _ => return Err(Error {}),
         }
@@ -288,12 +310,12 @@ impl<'a> VM {
     fn op_gteq(&mut self) -> Result<(), Error> {
         let left = self.pop()?;
         let right = self.pop()?;
-        match (left, right) {
+        match (left.as_ref(), right.as_ref()) {
-            (P(Int(i)), P(Int(ii))) => {
+            (&P(Int(i)), &P(Int(ii))) => {
-                self.push(P(Bool(i >= ii)))?;
+                self.push(Rc::new(P(Bool(i >= ii))))?;
             }
-            (P(Float(f)), P(Float(ff))) => {
+            (&P(Float(f)), &P(Float(ff))) => {
-                self.push(P(Bool(f >= ff)))?;
+                self.push(Rc::new(P(Bool(f >= ff))))?;
             }
             _ => return Err(Error {}),
         }
@@ -305,7 +327,7 @@ impl<'a> VM {
         let left = self.pop()?;
         let right = self.pop()?;
         // Then pushes the result onto the stack.
-        self.push(P(self.add(left, right)?))?;
+        self.push(Rc::new(P(self.add(&left, &right)?)))?;
         Ok(())
     }
 
@@ -314,7 +336,7 @@ impl<'a> VM {
         let left = self.pop()?;
         let right = self.pop()?;
         // Then pushes the result onto the stack.
-        self.push(P(self.sub(left, right)?))?;
+        self.push(Rc::new(P(self.sub(&left, &right)?)))?;
         Ok(())
     }
 
@@ -323,7 +345,7 @@ impl<'a> VM {
         let left = self.pop()?;
         let right = self.pop()?;
         // Then pushes the result onto the stack.
-        self.push(P(self.mul(left, right)?))?;
+        self.push(Rc::new(P(self.mul(&left, &right)?)))?;
         Ok(())
     }
 
@@ -332,7 +354,7 @@ impl<'a> VM {
         let left = self.pop()?;
         let right = self.pop()?;
         // Then pushes the result onto the stack.
-        self.push(P(self.div(left, right)?))?;
+        self.push(Rc::new(P(self.div(&left, &right)?)))?;
         Ok(())
     }
 
@@ -341,8 +363,8 @@ impl<'a> VM {
         let val = dbg!(self.pop())?;
         // pop name off stack.
         let name = dbg!(self.pop())?;
-        if let S(name) = name {
+        if let &S(ref name) = name.as_ref() {
-            self.binding_push(name, val)?;
+            self.binding_push(name.clone(), val)?;
         } else {
             return Err(Error {});
         }
@@ -354,18 +376,22 @@ impl<'a> VM {
         // get value from stack
         let val = self.pop()?;
         // get name from stack.
-        let name = if let S(s) | P(Str(s)) = self.pop()? {
+        let name_val = self.pop()?;
+        let name = if let &S(ref s) | &P(Str(ref s)) = name_val.as_ref() {
             s
         } else {
             return Err(Error {});
         };
         // get composite tuple from stack
         let tpl = self.pop()?;
-        if let C(Tuple(mut flds)) = tpl {
+        if let &C(Tuple(ref flds)) = tpl.as_ref() {
             // add name and value to tuple
-            self.merge_field_into_tuple(&mut flds, name, val)?;
+            // TODO(jwall): This is probably memory inefficient and we should
+            // optimize it a bit.
+            let mut flds = flds.clone();
+            self.merge_field_into_tuple(&mut flds, name.clone(), val)?;
             // place composite tuple back on stack
-            self.push(C(Tuple(flds)))?;
+            self.push(Rc::new(C(Tuple(flds))))?;
         } else {
             return Err(Error {});
         };
@@ -377,20 +403,23 @@ impl<'a> VM {
         let val = self.pop()?;
         // get next value. It should be a Composite list.
         let tpl = self.pop()?;
-        if let C(List(mut elems)) = tpl {
+        if let &C(List(ref elems)) = tpl.as_ref() {
             // add value to list
+            // TODO(jwall): This is probably memory inefficient and we should
+            // optimize it a bit.
+            let mut elems = elems.clone();
             elems.push(val);
             // Add that value to the list and put list back on stack.
-            self.push(C(List(elems)))?;
+            self.push(Rc::new(C(List(elems))))?;
         } else {
             return Err(Error {});
         };
         Ok(())
     }
 
-    fn find_in_list(&self, index: Value, elems: Vec<Value>) -> Result<Value, Error> {
+    fn find_in_list(&self, index: &Value, elems: &Vec<Rc<Value>>) -> Result<Rc<Value>, Error> {
         let idx = match index {
-            P(Int(i)) => i,
+            P(Int(i)) => i.clone(),
             _ => return dbg!(Err(Error {})),
         };
         match elems.get(idx as usize) {
@@ -399,21 +428,21 @@ impl<'a> VM {
         }
     }
 
-    fn find_in_flds(&self, index: Value, flds: Vec<(String, Value)>) -> Result<Value, Error> {
+    fn find_in_flds(&self, index: &Value, flds: &Vec<(String, Rc<Value>)>) -> Result<Rc<Value>, Error> {
         let idx = match index {
             S(p) => p,
             P(Str(p)) => p,
             _ => return dbg!(Err(Error {})),
         };
         for f in flds.iter() {
-            if idx == f.0 {
+            if idx == &f.0 {
                 return Ok(f.1.clone());
             }
         }
         Err(Error {})
     }
 
-    fn find_in_value(&self, index: Value, target: Value) -> Result<Value, Error> {
+    fn find_in_value(&self, index: &Value, target: &Value) -> Result<Rc<Value>, Error> {
         match target {
             C(Tuple(flds)) => self.find_in_flds(index, flds),
             C(List(elements)) => self.find_in_list(index, elements),
@@ -422,17 +451,19 @@ impl<'a> VM {
     }
 
     fn op_index(&mut self) -> Result<(), Error> {
-        let path = if let C(List(elems)) = self.pop()? {
+        let path_val = self.pop()?;
-            elems
+        let path = if let &C(List(ref elems)) = path_val.as_ref() {
+            elems.clone()
         } else {
             return dbg!(Err(Error {}));
         };
-        match self.pop()? {
+        let target_val = self.pop()?;
-            P(_) | S(_) | T(_) | F(_) | M(_) => return dbg!(Err(Error {})),
+        match target_val.as_ref() {
-            val => {
+            &P(_) | &S(_) | &T(_) | &F(_) | &M(_) => return dbg!(Err(Error {})),
-                let mut out = val;
+            _ => {
+                let mut out = target_val.clone();
                 for p in path {
-                    let tgt = self.find_in_value(p, out)?;
+                    let tgt = self.find_in_value(&p, &out)?;
                     out = tgt;
                 }
                 self.push(out)?;
@@ -446,50 +477,47 @@ impl<'a> VM {
         // get next value. It should be a Module or Tuple.
         let tgt = dbg!(self.pop())?;
         // This value should always be a tuple
-        let overrides = if let C(Tuple(oflds)) = self.pop()? {
+        let override_val = self.pop()?;
-            oflds
+        let overrides = if let &C(Tuple(ref oflds)) = override_val.as_ref() {
+            oflds.clone()
         } else {
             return dbg!(Err(Error {}));
         };
-        match tgt {
+        match tgt.as_ref() {
-            C(Tuple(mut flds)) => {
+            &C(Tuple(ref flds)) => {
+                let mut flds = flds.clone();
                 for (name, val) in overrides {
                     dbg!(self.merge_field_into_tuple(&mut flds, name, val))?;
                 }
                 // Put the copy on the Stack
-                self.push(C(Tuple(flds)))?;
+                self.push(Rc::new(C(Tuple(flds))))?;
             }
-            M(Module {
+            &M(Module {
-                ptr,
+                ref ptr,
-                result_ptr,
+                ref result_ptr,
-                mut flds,
+                ref flds,
             }) => {
                 //let this = M(Module {
                 //    ptr: ptr.clone(),
                 //    result_ptr: result_ptr.clone(),
                 //    flds: flds.clone(),
                 //});
+                let mut flds = flds.clone();
                 for (name, val) in overrides {
                     self.merge_field_into_tuple(&mut flds, name, val)?;
                 }
                 // FIXME(jwall): We need to populate the pkg key for modules.
                 //self.merge_field_into_tuple(&mut flds, "this".to_owned(), this)?;
-                let mut vm = Self::with_pointer(ptr);
+                let mut vm = Self::with_pointer(ptr.clone());
-                vm.push(S("mod".to_owned()))?;
+                vm.push(Rc::new(S("mod".to_owned())))?;
-                vm.push(C(Tuple(dbg!(flds))))?;
+                vm.push(Rc::new(C(Tuple(dbg!(flds)))))?;
                 vm.run()?;
-                let mut flds = Vec::new();
                 if let Some(ptr) = dbg!(result_ptr) {
-                    vm.ops.jump(ptr)?;
+                    vm.ops.jump(ptr.clone())?;
                     vm.run()?;
                     self.push(vm.pop()?)?;
                 } else {
-                    for sym in vm.symbols.symbol_list() {
+                    self.push(dbg!(Rc::new(vm.symbols_to_tuple(false))))?;
-                        if sym != "mod" {
-                            flds.push((sym.clone(), vm.symbols.get(sym).unwrap().clone()));
-                        }
-                    }
-                    self.push(dbg!(C(Tuple(flds))))?;
                 }
             }
             _ => {
@@ -501,9 +529,9 @@ impl<'a> VM {
 
     fn merge_field_into_tuple(
         &self,
-        src_fields: &'a mut Vec<(String, Value)>,
+        src_fields: &'a mut Vec<(String, Rc<Value>)>,
         name: String,
-        value: Value,
+        value: Rc<Value>,
     ) -> Result<(), Error> {
         for fld in src_fields.iter_mut() {
             if fld.0 == name {
@@ -515,12 +543,12 @@ impl<'a> VM {
         Ok(())
     }
 
-    fn push(&mut self, p: Value) -> Result<(), Error> {
+    fn push(&mut self, p: Rc<Value>) -> Result<(), Error> {
         self.stack.push(p);
         Ok(())
     }
 
-    fn binding_push(&mut self, name: String, val: Value) -> Result<(), Error> {
+    fn binding_push(&mut self, name: String, val: Rc<Value>) -> Result<(), Error> {
         if self.symbols.is_bound(&name) {
             return Err(Error {});
         }
@@ -528,21 +556,21 @@ impl<'a> VM {
         Ok(())
     }
 
-    pub fn get_binding(&'a self, name: &str) -> Result<&Value, Error> {
+    pub fn get_binding(&'a self, name: &str) -> Result<Rc<Value>, Error> {
         match self.symbols.get(name) {
             Some(v) => Ok(v),
             None => Err(Error {}),
         }
     }
 
-    pub fn pop(&mut self) -> Result<Value, Error> {
+    pub fn pop(&mut self) -> Result<Rc<Value>, Error> {
         match self.stack.pop() {
             Some(v) => Ok(v),
             None => Err(Error {}),
         }
     }
 
-    fn mul(&self, left: Value, right: Value) -> Result<Primitive, Error> {
+    fn mul(&self, left: &Value, right: &Value) -> Result<Primitive, Error> {
         Ok(match (left, right) {
             (P(Int(i)), P(Int(ii))) => Int(i * ii),
             (P(Float(f)), P(Float(ff))) => Float(f * ff),
@@ -550,7 +578,7 @@ impl<'a> VM {
         })
     }
 
-    fn div(&self, left: Value, right: Value) -> Result<Primitive, Error> {
+    fn div(&self, left: &Value, right: &Value) -> Result<Primitive, Error> {
         Ok(match (left, right) {
             (P(Int(i)), P(Int(ii))) => Int(i / ii),
             (P(Float(f)), P(Float(ff))) => Float(f / ff),
@@ -558,7 +586,7 @@ impl<'a> VM {
         })
     }
 
-    fn sub(&self, left: Value, right: Value) -> Result<Primitive, Error> {
+    fn sub(&self, left: &Value, right: &Value) -> Result<Primitive, Error> {
         Ok(match (left, right) {
             (P(Int(i)), Value::P(Int(ii))) => Int(i - ii),
             (P(Float(f)), Value::P(Float(ff))) => Float(f - ff),
@@ -566,7 +594,7 @@ impl<'a> VM {
         })
     }
 
-    fn add(&self, left: Value, right: Value) -> Result<Primitive, Error> {
+    fn add(&self, left: &Value, right: &Value) -> Result<Primitive, Error> {
         Ok(match (left, right) {
             (P(Int(i)), Value::P(Int(ii))) => Int(i + ii),
             (P(Float(f)), Value::P(Float(ff))) => Float(f + ff),
@@ -579,4 +607,8 @@ impl<'a> VM {
             _ => return Err(Error {}),
         })
     }
-}
+
+    fn op_runtime(&mut self, h: Hook) -> Result<(), Error> {
+        self.runtime.borrow_mut().handle(h, &mut self.stack)
+    }
+}