diff --git a/src/compiler.cpp b/src/compiler.cpp
index a9e15f6..dbe01e6 100644
--- a/src/compiler.cpp
+++ b/src/compiler.cpp
@@ -1,17 +1,41 @@
 #include "compiler.hpp"
 
-Result<Value> Compiler::compile(Value& expr) {
-  auto env = TRY(Array::create(_arena));
-  auto constants = TRY(Array::create(_arena));
+struct Context {
+  Context() {}
+  Context(Value&& env, Array&& constants)
+      : env(std::move(env)),
+        constants(std::move(constants)),
+        maxreg(0),
+        maxconst(0) {}
 
-  return compile_expr(expr);
+  static Result<Context> create(Arena& arena) {
+    auto env = TRY(Nil::create(arena));
+    auto constants = TRY(Array::create(arena));
+
+    return Context(std::move(env), std::move(constants));
+  }
+
+  Value env;
+  Array constants;
+  uint64_t maxreg;
+  uint64_t maxconst;
+};
+
+bool is_primitive_op(Symbol& sym) {
+  // return (sym.cmp("+") == 0);
+  return false;
 }
-Result<Value> Compiler::compile_expr(Value& expr) {
-  return Value(TRY(Nil::create(_arena)));
 
+Result<Value> Compiler::compile(Value& expr) {
+  auto context = TRY(Context::create(_arena));
+
+  TRY(compile_expr(context, expr));
+  return ErrorCode::NotImplemented;
+}
+Result<Expression> Compiler::compile_expr(Context& context, Value& expr) {
   switch (expr.tag()) {
     case Tag::Pair:
-      return compile_list(*expr.to<Pair>());
+      return compile_list(context, *expr.to<Pair>());
     case Tag::Nil:
     case Tag::Bool:
     case Tag::Int64:
@@ -27,7 +51,11 @@ Result<Value> Compiler::compile_expr(Value& expr) {
   return ErrorCode::TypeMismatch;
 }
 
-Result<Value> Compiler::compile_list(Pair& expr) {
+Result<Expression> Compiler::compile_list(Context& context, Pair& expr) {
   auto first = TRY(expr.first(_arena));
+
+  if (first.is<Symbol>()) {
+    Symbol& sym = *first.to<Symbol>();
+  }
   return ErrorCode::TypeMismatch;
 }
diff --git a/src/compiler.hpp b/src/compiler.hpp
index 972d610..10c0e94 100644
--- a/src/compiler.hpp
+++ b/src/compiler.hpp
@@ -2,13 +2,22 @@
 
 #include "common.hpp"
 
+struct Context;
+
+struct Expression {
+  Expression() {}
+  Expression(uint64_t reg, Array&& code) : reg(reg), code(std::move(code)) {}
+  uint64_t reg;
+  Array code;
+};
+
 class Compiler {
  public:
   Compiler(Arena& arena) : _arena(arena) {}
 
   Result<Value> compile(Value& expr);
-  Result<Value> compile_expr(Value& expr);
-  Result<Value> compile_list(Pair& expr);
+  Result<Expression> compile_expr(Context& context, Value& expr);
+  Result<Expression> compile_list(Context& context, Pair& expr);
 
  private:
   Arena& _arena;
diff --git a/src/vli.cpp b/src/vli.cpp
index b7c3dc8..08a6779 100644
--- a/src/vli.cpp
+++ b/src/vli.cpp
@@ -22,7 +22,7 @@ int main() {
   DIEX(debug_print(arena, s2));
 
   Compiler c = Compiler(arena);
-  auto compiled = DIEX(c.compile_expr(r));
+  auto compiled = DIEX(c.compile(r));
 
   return 0;
 }