diff --git a/lib/irgen.ml b/lib/irgen.ml
index d02f06d..86d2672 100644
--- a/lib/irgen.ml
+++ b/lib/irgen.ml
@@ -26,7 +26,10 @@ and l_float = L.float_type context
 
 let l_str = L.pointer_type l_char
 
-let rec ltype_of_typ = function
+(* A list is a wrapper struct containing length and a pointer to the array *)
+let l_list = L.struct_type context [| l_int; l_str |]
+
+let ltype_of_typ = function
   | RInt -> l_int
   | RBool -> l_bool
   | RFloat -> l_float
@@ -34,7 +37,8 @@ let rec ltype_of_typ = function
   | RUnit -> l_unit
   | RString -> l_str
   | REnumType _ -> l_int
-  | RList typ -> L.pointer_type (ltype_of_typ typ)
+  | RList _ ->
+    L.pointer_type l_list (* Not an accident - supposed to be a pointer to list struct *)
   | RUserType name ->
     (try Hashtbl.find udt_structs name with
      | Not_found -> raise (Failure ("Unknown user type: " ^ name)))
@@ -322,8 +326,20 @@ let rec build_expr expr (vars : variable StringMap.t) var_types the_module build
     field_val
   | SList list ->
     let typ = fst (List.hd list) in
-    let lval = L.const_int l_int (List.length list) in
-    let llist = L.build_array_alloca (ltype_of_typ typ) lval "list" builder in
+    let llen = L.const_int l_int (List.length list) in
+
+    let llist_shell = L.build_alloca l_list "list_shell" builder in
+    let len_ptr = L.build_struct_gep llist_shell 0 "len_ptr" builder in
+    ignore (L.build_store llen len_ptr builder);
+
+    let llist = L.build_array_alloca (ltype_of_typ typ) llen "list" builder in
+    let llist_cast =
+      L.build_pointercast llist (L.pointer_type (L.i8_type context)) "llist_cast" builder
+    in
+    let data_ptr = L.build_struct_gep llist_shell 1 "data_ptr" builder in
+
+    ignore (L.build_store llist_cast data_ptr builder);
+
     List.iteri
       (fun idx item ->
          let litem = build_expr item vars var_types the_module builder in
@@ -332,12 +348,37 @@ let rec build_expr expr (vars : variable StringMap.t) var_types the_module build
          in
          ignore (L.build_store litem lidx builder))
       list;
-    llist
+    llist_shell
   | SStringLit s -> L.build_global_stringptr s "str" builder
   | SIndex (list_expr, index_expr) ->
-    let list_val = build_expr list_expr vars var_types the_module builder in
+    (* the list_expr should be an SId and nothing else right? *)
+    let var_name =
+      match snd list_expr with
+      | SId i -> i
+      | _ -> failwith "bad list_expr"
+    in
+
+    let vbl = lookup vars var_name in
+    let list_val = vbl.v_value in
+    let typ =
+      match vbl.v_type with
+      | RList t -> t
+      | _ -> failwith "type should be list"
+    in
+
+    let loaded_list_val = L.build_load list_val "loaded_list" builder in
+
     let index_val = build_expr index_expr vars var_types the_module builder in
-    let elem_ptr = L.build_gep list_val [| index_val |] "elem_ptr" builder in
+
+    (* bitcast the array pointer type back to the appropriate value *)
+    let raw_larr_ptr = L.build_struct_gep loaded_list_val 1 "raw_arr_ptr" builder in
+    let i8_arr = L.build_load raw_larr_ptr "i8_arr" builder in
+    let larr_ptr =
+      L.build_bitcast i8_arr (L.pointer_type (ltype_of_typ typ)) "arr_ptr" builder
+    in
+
+    let elem_ptr = L.build_gep larr_ptr [| index_val |] "elem_ptr" builder in
+
     (match fst expr with
      | RInt | RFloat | RString | RBool | REnumType _ ->
        L.build_load elem_ptr "elem_val" builder
@@ -400,17 +441,22 @@ and prelude_print (func : sfunc) vars var_types the_module builder =
 and prelude_len (func : sfunc) vars var_types the_module builder =
   let func_arg = List.hd (snd func) in
   let lexpr = build_expr func_arg vars var_types the_module builder in
-  let args =
-    match fst func_arg with
-    | RString -> [| lexpr |]
-    | t ->
-      failwith
-        (Printf.sprintf
-           "prelude_len not implemented for type: %s"
-           (Utils.string_of_resolved_type t))
-  in
 
-  L.build_call (strlen_func the_module) args "call_strlen" builder
+  match fst func_arg with
+  | RString ->
+    let args = [| lexpr |] in
+
+    L.build_call (strlen_func the_module) args "call_strlen" builder
+  | RList _l ->
+    flush stdout;
+    let len_ptr = L.build_struct_gep lexpr 0 "len_ptr" builder in
+    let len_val = L.build_load len_ptr "lislen" builder in
+    len_val
+  | t ->
+    failwith
+      (Printf.sprintf
+         "prelude_len not implemented for type: %s"
+         (Utils.string_of_resolved_type t))
 
 and prelude_input (_func : sfunc) _vars _var_types the_module builder =
   (* The max buffer size for reading strings *)
diff --git a/test/ir/test_list.ml b/test/ir/test_list.ml
index 1c8b4fe..e36ece2 100644
--- a/test/ir/test_list.ml
+++ b/test/ir/test_list.ml
@@ -27,7 +27,7 @@ let _write_to_file text filename =
 
 let tests =
   "testing_lists"
-  >::: [ ("local_list"
+  >::: [ ("local_int_list"
           >:: fun _ ->
           let sast = get_sast "fun function() -> () {let a := [10, 20, 30];}" in
           let mdl = Irgen.translate sast in
@@ -37,15 +37,23 @@ let tests =
              source_filename = \"Fly\"\n\n\
              define void @function() {\n\
              entry:\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 3, i32* %len_ptr, align 4\n\
             \  %list = alloca i32, i32 3, align 4\n\
+            \  %llist_cast = bitcast i32* %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
             \  %index = getelementptr inbounds i32, i32* %list, i32 0\n\
             \  store i32 10, i32* %index, align 4\n\
             \  %index1 = getelementptr inbounds i32, i32* %list, i32 1\n\
             \  store i32 20, i32* %index1, align 4\n\
             \  %index2 = getelementptr inbounds i32, i32* %list, i32 2\n\
             \  store i32 30, i32* %index2, align 4\n\
-            \  %a = alloca i32*, align 8\n\
-            \  store i32* %list, i32** %a, align 8\n\
+            \  %a = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %a, align 8\n\
             \  ret void\n\
              }\n"
           in
@@ -60,17 +68,26 @@ let tests =
              source_filename = \"Fly\"\n\n\
              define void @function() {\n\
              entry:\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 2, i32* %len_ptr, align 4\n\
             \  %list = alloca i1, i32 2, align 1\n\
+            \  %llist_cast = bitcast i1* %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
             \  %index = getelementptr inbounds i1, i1* %list, i32 0\n\
             \  store i1 true, i1* %index, align 1\n\
             \  %index1 = getelementptr inbounds i1, i1* %list, i32 1\n\
             \  store i1 false, i1* %index1, align 1\n\
-            \  %a = alloca i1*, align 8\n\
-            \  store i1* %list, i1** %a, align 8\n\
+            \  %a = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %a, align 8\n\
             \  ret void\n\
              }\n"
           in
           _write_to_file actual "actual.out";
+          _write_to_file expected "expected.out";
           assert_equal expected actual ~printer)
        ; ("local_string_list"
           >:: fun _ ->
@@ -84,19 +101,28 @@ let tests =
              @str.1 = private unnamed_addr constant [6 x i8] c\"world\\00\", align 1\n\n\
              define void @function() {\n\
              entry:\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 2, i32* %len_ptr, align 4\n\
             \  %list = alloca i8*, i32 2, align 8\n\
+            \  %llist_cast = bitcast i8** %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
             \  %index = getelementptr inbounds i8*, i8** %list, i32 0\n\
             \  store i8* getelementptr inbounds ([6 x i8], [6 x i8]* @str, i32 0, i32 \
              0), i8** %index, align 8\n\
             \  %index1 = getelementptr inbounds i8*, i8** %list, i32 1\n\
             \  store i8* getelementptr inbounds ([6 x i8], [6 x i8]* @str.1, i32 0, i32 \
              0), i8** %index1, align 8\n\
-            \  %a = alloca i8**, align 8\n\
-            \  store i8** %list, i8*** %a, align 8\n\
+            \  %a = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %a, align 8\n\
             \  ret void\n\
              }\n"
           in
-          (* _write_to_file actual "actual.out"; *)
+          _write_to_file actual "actual.out";
+          _write_to_file expected "expected.out";
           assert_equal expected actual ~printer)
        ; ("local_int_list_index"
           >:: fun _ ->
@@ -108,15 +134,27 @@ let tests =
              source_filename = \"Fly\"\n\n\
              define i32 @function() {\n\
              entry:\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 2, i32* %len_ptr, align 4\n\
             \  %list = alloca i32, i32 2, align 4\n\
+            \  %llist_cast = bitcast i32* %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
             \  %index = getelementptr inbounds i32, i32* %list, i32 0\n\
             \  store i32 1, i32* %index, align 4\n\
             \  %index1 = getelementptr inbounds i32, i32* %list, i32 1\n\
             \  store i32 2, i32* %index1, align 4\n\
-            \  %a = alloca i32*, align 8\n\
-            \  store i32* %list, i32** %a, align 8\n\
-            \  %a2 = load i32*, i32** %a, align 8\n\
-            \  %elem_ptr = getelementptr i32, i32* %a2, i32 0\n\
+            \  %a = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %a, align 8\n\
+            \  %loaded_list = load { i32, i8* }*, { i32, i8* }** %a, align 8\n\
+            \  %raw_arr_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %loaded_list, i32 0, i32 1\n\
+            \  %i8_arr = load i8*, i8** %raw_arr_ptr, align 8\n\
+            \  %arr_ptr = bitcast i8* %i8_arr to i32*\n\
+            \  %elem_ptr = getelementptr i32, i32* %arr_ptr, i32 0\n\
             \  %elem_val = load i32, i32* %elem_ptr, align 4\n\
             \  ret i32 %elem_val\n\
              }\n"
@@ -151,22 +189,68 @@ let tests =
             \  %Point_y3 = getelementptr inbounds { i32, i32 }, { i32, i32 }* \
              %Point_inst1, i32 0, i32 1\n\
             \  store i32 4, i32* %Point_y3, align 4\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 2, i32* %len_ptr, align 4\n\
             \  %list = alloca { i32, i32 }, i32 2, align 8\n\
+            \  %llist_cast = bitcast { i32, i32 }* %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
             \  %index = getelementptr inbounds { i32, i32 }, { i32, i32 }* %list, i32 0\n\
             \  store { i32, i32 }* %Point_inst, { i32, i32 }* %index, align 8\n\
             \  %index4 = getelementptr inbounds { i32, i32 }, { i32, i32 }* %list, i32 1\n\
             \  store { i32, i32 }* %Point_inst1, { i32, i32 }* %index4, align 8\n\
-            \  %arr = alloca { i32, i32 }*, align 8\n\
-            \  store { i32, i32 }* %list, { i32, i32 }** %arr, align 8\n\
-            \  %arr5 = load { i32, i32 }*, { i32, i32 }** %arr, align 8\n\
-            \  %elem_ptr = getelementptr { i32, i32 }, { i32, i32 }* %arr5, i32 1\n\
+            \  %arr = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %arr, align 8\n\
+            \  %loaded_list = load { i32, i8* }*, { i32, i8* }** %arr, align 8\n\
+            \  %raw_arr_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %loaded_list, i32 0, i32 1\n\
+            \  %i8_arr = load i8*, i8** %raw_arr_ptr, align 8\n\
+            \  %arr_ptr = bitcast i8* %i8_arr to { i32, i32 }*\n\
+            \  %elem_ptr = getelementptr { i32, i32 }, { i32, i32 }* %arr_ptr, i32 1\n\
             \  %arr_y = getelementptr inbounds { i32, i32 }, { i32, i32 }* %elem_ptr, \
              i32 0, i32 1\n\
             \  %arr_y_val = load i32, i32* %arr_y, align 4\n\
             \  ret i32 %arr_y_val\n\
              }\n"
           in
+          _write_to_file actual "actual.out";
+          _write_to_file expected "expected.out";
+          (* _write_to_file actual "actual.out"; *)
           assert_equal expected actual ~printer)
+         (* ; ("global_int_list" *)
+         (*    >:: fun _ -> *)
+         (*    let sast = get_sast "let a := [10, 20, 30];" in *)
+         (*    let mdl = Irgen.translate sast in *)
+         (*    let actual = L.string_of_llmodule mdl in *)
+         (*    let expected = *)
+         (*      "; ModuleID = 'Fly'\n\ *)
+       (*       source_filename = \"Fly\"\n\n\ *)
+       (*       define void @function() {\n\ *)
+       (*       entry:\n\ *)
+       (*      \  %list_shell = alloca { i32, i8* }, align 8\n\ *)
+       (*      \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \ *)
+       (*       %list_shell, i32 0, i32 0\n\ *)
+       (*      \  store i32 3, i32* %len_ptr, align 4\n\ *)
+       (*      \  %list = alloca i32, i32 3, align 4\n\ *)
+       (*      \  %llist_cast = bitcast i32* %list to i8*\n\ *)
+       (*      \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \ *)
+       (*       %list_shell, i32 0, i32 1\n\ *)
+       (*      \  store i8* %llist_cast, i8** %data_ptr, align 8\n\ *)
+       (*      \  %index = getelementptr inbounds i32, i32* %list, i32 0\n\ *)
+       (*      \  store i32 10, i32* %index, align 4\n\ *)
+       (*      \  %index1 = getelementptr inbounds i32, i32* %list, i32 1\n\ *)
+       (*      \  store i32 20, i32* %index1, align 4\n\ *)
+       (*      \  %index2 = getelementptr inbounds i32, i32* %list, i32 2\n\ *)
+       (*      \  store i32 30, i32* %index2, align 4\n\ *)
+       (*      \  %a = alloca { i32, i8* }*, align 8\n\ *)
+       (*      \  store { i32, i8* }* %list_shell, { i32, i8* }** %a, align 8\n\ *)
+       (*      \  ret void\n\ *)
+       (*       }\n" *)
+         (*    in *)
+         (*    assert_equal expected actual ~printer) *)
        ; ("list_of_enums_index"
           >:: fun _ ->
           let sast =
diff --git a/test/ir/test_prelude.ml b/test/ir/test_prelude.ml
index be64c57..9048d1b 100644
--- a/test/ir/test_prelude.ml
+++ b/test/ir/test_prelude.ml
@@ -132,7 +132,7 @@ let tests =
           in
           (* _write_to_file actual "test.out"; *)
           assert_equal expected actual ~printer)
-       ; ("len"
+       ; ("len_of_string"
           >:: fun _ ->
           let sast =
             get_sast "fun main() {let str := \"hello\"; let strlen := len(str); }"
@@ -158,6 +158,44 @@ let tests =
           in
           (* _write_to_file actual "actual.out"; *)
           assert_equal expected actual ~printer)
+       ; ("len_of_list"
+          >:: fun _ ->
+          let sast =
+            get_sast "fun main() {let lis := [10, 20]; let lislen := len(lis); }"
+          in
+          let mdl = Irgen.translate sast in
+          let actual = L.string_of_llmodule mdl in
+          let expected =
+            "; ModuleID = 'Fly'\n\
+             source_filename = \"Fly\"\n\n\
+             define void @main() {\n\
+             entry:\n\
+            \  %list_shell = alloca { i32, i8* }, align 8\n\
+            \  %len_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 0\n\
+            \  store i32 2, i32* %len_ptr, align 4\n\
+            \  %list = alloca i32, i32 2, align 4\n\
+            \  %llist_cast = bitcast i32* %list to i8*\n\
+            \  %data_ptr = getelementptr inbounds { i32, i8* }, { i32, i8* }* \
+             %list_shell, i32 0, i32 1\n\
+            \  store i8* %llist_cast, i8** %data_ptr, align 8\n\
+            \  %index = getelementptr inbounds i32, i32* %list, i32 0\n\
+            \  store i32 10, i32* %index, align 4\n\
+            \  %index1 = getelementptr inbounds i32, i32* %list, i32 1\n\
+            \  store i32 20, i32* %index1, align 4\n\
+            \  %lis = alloca { i32, i8* }*, align 8\n\
+            \  store { i32, i8* }* %list_shell, { i32, i8* }** %lis, align 8\n\
+            \  %lis2 = load { i32, i8* }*, { i32, i8* }** %lis, align 8\n\
+            \  %len_ptr3 = getelementptr inbounds { i32, i8* }, { i32, i8* }* %lis2, i32 \
+             0, i32 0\n\
+            \  %lislen = load i32, i32* %len_ptr3, align 4\n\
+            \  %lislen4 = alloca i32, align 4\n\
+            \  store i32 %lislen, i32* %lislen4, align 4\n\
+            \  ret void\n\
+             }\n"
+          in
+          (* _write_to_file actual "actual.out"; *)
+          assert_equal expected actual ~printer)
        ; ("input"
           >:: fun _ ->
           let sast = get_sast "fun main() {let str := input(); return; }" in