Change object representation from 1 big union to individual structs.

A big change.  Micro Python objects are allocated as individual structs
with the first element being a pointer to the type information (which
is itself an object).  This scheme follows CPython.  Much more flexible,
not necessarily slower, uses same heap memory, and can allocate objects
statically.

Also change name prefix, from py_ to mp_ (mp for Micro Python).

1 files changed, 304 insertions, 942 deletions

diff --git a/py/runtime.c b/py/runtime.c
index 35f4f2af29..a3d11f3c6c 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -1,23 +1,20 @@
 // in principle, rt_xxx functions are called only by vm/native/viper and make assumptions about args
-// py_xxx functions are safer and can be called by anyone
+// mp_xxx functions are safer and can be called by anyone
 // note that rt_assign_xxx are called only from emit*, and maybe we can rename them to reflect this
 
 #include <stdint.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include <stdarg.h>
 #include <string.h>
 #include <assert.h>
 
 #include "nlr.h"
 #include "misc.h"
-#include "mpyconfig.h"
+#include "mpconfig.h"
+#include "obj.h"
+#include "runtime0.h"
 #include "runtime.h"
-#include "bc.h"
-
 #include "map.h"
-#include "obj.h"
-#include "objprivate.h"
 #include "builtin.h"
 
 #if 0 // print debugging info
@@ -46,203 +43,20 @@ qstr rt_q_TypeError;
 qstr rt_q_SyntaxError;
 qstr rt_q_ValueError;
 
-py_obj_t py_const_none;
-py_obj_t py_const_false;
-py_obj_t py_const_true;
-py_obj_t py_const_stop_iteration;
-
 // locals and globals need to be pointers because they can be the same in outer module scope
-static py_map_t *map_locals;
-static py_map_t *map_globals;
-static py_map_t map_builtins;
-
-py_map_t *rt_get_map_locals(void) {
-    return map_locals;
-}
-
-void rt_set_map_locals(py_map_t *m) {
-    map_locals = m;
-}
-
-static bool fit_small_int(py_small_int_t o) {
-    return true;
-}
-
-int rt_is_true(py_obj_t arg) {
-    DEBUG_OP_printf("is true %p\n", arg);
-    if (IS_SMALL_INT(arg)) {
-        if (FROM_SMALL_INT(arg) == 0) {
-            return 0;
-        } else {
-            return 1;
-        }
-    } else if (arg == py_const_none) {
-        return 0;
-    } else if (arg == py_const_false) {
-        return 0;
-    } else if (arg == py_const_true) {
-        return 1;
-    } else {
-        assert(0);
-        return 0;
-    }
-}
-
-void vstr_printf_wrapper(void *env, const char *fmt, ...) {
-    va_list args;
-    va_start(args, fmt);
-    vstr_vprintf(env, fmt, args);
-    va_end(args);
-}
-
-py_obj_t rt_str_join(py_obj_t self_in, py_obj_t arg) {
-    assert(IS_O(self_in, O_STR));
-    py_obj_base_t *self = self_in;
-    int required_len = strlen(qstr_str(self->u_str));
-
-    // process arg, count required chars
-    if (!IS_O(arg, O_TUPLE) && !IS_O(arg, O_LIST)) {
-        goto bad_arg;
-    }
-    py_obj_base_t *tuple_list = arg;
-    for (int i = 0; i < tuple_list->u_tuple_list.len; i++) {
-        if (!IS_O(tuple_list->u_tuple_list.items[i], O_STR)) {
-            goto bad_arg;
-        }
-        required_len += strlen(qstr_str(((py_obj_base_t*)tuple_list->u_tuple_list.items[i])->u_str));
-    }
-
-    // make joined string
-    char *joined_str = m_new(char, required_len + 1);
-    joined_str[0] = 0;
-    for (int i = 0; i < tuple_list->u_tuple_list.len; i++) {
-        const char *s2 = qstr_str(((py_obj_base_t*)tuple_list->u_tuple_list.items[i])->u_str);
-        if (i > 0) {
-            strcat(joined_str, qstr_str(self->u_str));
-        }
-        strcat(joined_str, s2);
-    }
-    return py_obj_new_str(qstr_from_str_take(joined_str));
-
-bad_arg:
-    nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "?str.join expecting a list of str's", NULL, NULL));
-}
-
-py_obj_t rt_str_format(int n_args, const py_obj_t *args) {
-    assert(IS_O(args[0], O_STR));
-    py_obj_base_t *self = args[0];
-
-    const char *str = qstr_str(self->u_str);
-    int arg_i = 1;
-    vstr_t *vstr = vstr_new();
-    for (; *str; str++) {
-        if (*str == '{') {
-            str++;
-            if (*str == '{') {
-                vstr_add_char(vstr, '{');
-            } else if (*str == '}') {
-                if (arg_i >= n_args) {
-                    nlr_jump(py_obj_new_exception_2(rt_q_IndexError, "tuple index out of range", NULL, NULL));
-                }
-                py_obj_print_helper(vstr_printf_wrapper, vstr, args[arg_i]);
-                arg_i++;
-            }
-        } else {
-            vstr_add_char(vstr, *str);
-        }
-    }
-
-    return py_obj_new_str(qstr_from_str_take(vstr->buf));
-}
-
-uint get_index(py_obj_base_t *base, py_obj_t index) {
-    // assumes base is O_TUPLE or O_LIST
-    // TODO False and True are considered 0 and 1 for indexing purposes
-    int len = base->u_tuple_list.len;
-    if (IS_SMALL_INT(index)) {
-        int i = FROM_SMALL_INT(index);
-        if (i < 0) {
-            i += len;
-        }
-        if (i < 0 || i >= len) {
-            nlr_jump(py_obj_new_exception_2(rt_q_IndexError, "%s index out of range", py_obj_get_type_str(base), NULL));
-        }
-        return i;
-    } else {
-        nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "%s indices must be integers, not %s", py_obj_get_type_str(base), py_obj_get_type_str(index)));
-    }
-}
-
-py_obj_t rt_list_append(py_obj_t self_in, py_obj_t arg) {
-    assert(IS_O(self_in, O_LIST));
-    py_obj_base_t *self = self_in;
-    if (self->u_tuple_list.len >= self->u_tuple_list.alloc) {
-        self->u_tuple_list.alloc *= 2;
-        self->u_tuple_list.items = m_renew(py_obj_t, self->u_tuple_list.items, self->u_tuple_list.alloc);
-    }
-    self->u_tuple_list.items[self->u_tuple_list.len++] = arg;
-    return py_const_none; // return None, as per CPython
-}
-
-py_obj_t rt_list_pop(py_obj_t self_in, py_obj_t arg) {
-    assert(IS_O(self_in, O_LIST));
-    py_obj_base_t *self = self_in;
-    uint index = get_index(self, arg);
-    py_obj_t ret = self->u_tuple_list.items[index];
-    self->u_tuple_list.len -= 1;
-    memcpy(self->u_tuple_list.items + index, self->u_tuple_list.items + index + 1, (self->u_tuple_list.len - index) * sizeof(py_obj_t));
-    return ret;
-}
-
-// TODO make this conform to CPython's definition of sort
-static void py_quicksort(py_obj_t *head, py_obj_t *tail, py_obj_t key_fn) {
-    while (head < tail) {
-        py_obj_t *h = head - 1;
-        py_obj_t *t = tail;
-        py_obj_t v = rt_call_function_1(key_fn, tail[0]); // get pivot using key_fn
-        for (;;) {
-            do ++h; while (rt_compare_op(RT_COMPARE_OP_LESS, rt_call_function_1(key_fn, h[0]), v) == py_const_true);
-            do --t; while (h < t && rt_compare_op(RT_COMPARE_OP_LESS, v, rt_call_function_1(key_fn, t[0])) == py_const_true);
-            if (h >= t) break;
-            py_obj_t x = h[0];
-            h[0] = t[0];
-            t[0] = x;
-        }
-        py_obj_t x = h[0];
-        h[0] = tail[0];
-        tail[0] = x;
-        py_quicksort(head, t, key_fn);
-        head = h + 1;
-    }
-}
-
-py_obj_t rt_list_sort(py_obj_t self_in, py_obj_t key_fn) {
-    assert(IS_O(self_in, O_LIST));
-    py_obj_base_t *self = self_in;
-    if (self->u_tuple_list.len > 1) {
-        py_quicksort(self->u_tuple_list.items, self->u_tuple_list.items + self->u_tuple_list.len - 1, key_fn);
-    }
-    return py_const_none; // return None, as per CPython
-}
-
-py_obj_t rt_gen_instance_next(py_obj_t self_in) {
-    py_obj_t ret = rt_iternext(self_in);
-    if (ret == py_const_stop_iteration) {
-        nlr_jump(py_obj_new_exception_0(qstr_from_str_static("StopIteration")));
-    } else {
-        return ret;
-    }
-}
+static mp_map_t *map_locals;
+static mp_map_t *map_globals;
+static mp_map_t map_builtins;
 
 typedef enum {
-    PY_CODE_NONE,
-    PY_CODE_BYTE,
-    PY_CODE_NATIVE,
-    PY_CODE_INLINE_ASM,
-} py_code_kind_t;
-
-typedef struct _py_code_t {
-    py_code_kind_t kind;
+    MP_CODE_NONE,
+    MP_CODE_BYTE,
+    MP_CODE_NATIVE,
+    MP_CODE_INLINE_ASM,
+} mp_code_kind_t;
+
+typedef struct _mp_code_t {
+    mp_code_kind_t kind;
     int n_args;
     int n_locals;
     int n_cells;
@@ -254,23 +68,16 @@ typedef struct _py_code_t {
             uint len;
         } u_byte;
         struct {
-            py_fun_t fun;
+            mp_fun_t fun;
         } u_native;
         struct {
             void *fun;
         } u_inline_asm;
     };
-} py_code_t;
+} mp_code_t;
 
 static int next_unique_code_id;
-static py_code_t *unique_codes;
-
-py_obj_t fun_str_join;
-py_obj_t fun_str_format;
-py_obj_t fun_list_append;
-py_obj_t fun_list_pop;
-py_obj_t fun_list_sort;
-py_obj_t fun_gen_instance_next;
+static mp_code_t *unique_codes;
 
 #ifdef WRITE_CODE
 FILE *fp_write_code = NULL;
@@ -292,50 +99,41 @@ void rt_init(void) {
     rt_q_SyntaxError = qstr_from_str_static("SyntaxError");
     rt_q_ValueError = qstr_from_str_static("ValueError");
 
-    py_const_none = py_obj_new_const("None");
-    py_const_false = py_obj_new_const("False");
-    py_const_true = py_obj_new_const("True");
-    py_const_stop_iteration = py_obj_new_const("StopIteration");
-
     // locals = globals for outer module (see Objects/frameobject.c/PyFrame_New())
-    map_locals = map_globals = py_map_new(MAP_QSTR, 1);
-    py_qstr_map_lookup(map_globals, qstr_from_str_static("__name__"), true)->value = py_obj_new_str(qstr_from_str_static("__main__"));
-
-    py_map_init(&map_builtins, MAP_QSTR, 3);
-    py_qstr_map_lookup(&map_builtins, rt_q___build_class__, true)->value = rt_make_function_2(py_builtin___build_class__);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("__repl_print__"), true)->value = rt_make_function_1(py_builtin___repl_print__);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("abs"), true)->value = rt_make_function_1(py_builtin_abs);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("all"), true)->value = rt_make_function_1(py_builtin_all);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("any"), true)->value = rt_make_function_1(py_builtin_any);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("bool"), true)->value = rt_make_function_var(0, py_builtin_bool);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("callable"), true)->value = rt_make_function_1(py_builtin_callable);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("complex"), true)->value = rt_make_function_var(0, py_builtin_complex);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("chr"), true)->value = rt_make_function_1(py_builtin_chr);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("dict"), true)->value = rt_make_function_0(py_builtin_dict);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("divmod"), true)->value = rt_make_function_2(py_builtin_divmod);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("hash"), true)->value = rt_make_function_1(py_builtin_hash);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("iter"), true)->value = rt_make_function_1(py_builtin_iter);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("len"), true)->value = rt_make_function_1(py_builtin_len);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("list"), true)->value = rt_make_function_var(0, py_builtin_list);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("max"), true)->value = rt_make_function_var(1, py_builtin_max);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("min"), true)->value = rt_make_function_var(1, py_builtin_min);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("next"), true)->value = rt_make_function_1(py_builtin_next);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("ord"), true)->value = rt_make_function_1(py_builtin_ord);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("pow"), true)->value = rt_make_function_var(2, py_builtin_pow);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("print"), true)->value = rt_make_function_var(0, py_builtin_print);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("range"), true)->value = rt_make_function_var(1, py_builtin_range);
-    py_qstr_map_lookup(&map_builtins, qstr_from_str_static("sum"), true)->value = rt_make_function_var(1, py_builtin_sum);
+    map_locals = map_globals = mp_map_new(MP_MAP_QSTR, 1);
+    mp_qstr_map_lookup(map_globals, qstr_from_str_static("__name__"), true)->value = mp_obj_new_str(qstr_from_str_static("__main__"));
+
+    mp_map_init(&map_builtins, MP_MAP_QSTR, 3);
+    mp_qstr_map_lookup(&map_builtins, rt_q___build_class__, true)->value = rt_make_function_2(mp_builtin___build_class__);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("__repl_print__"), true)->value = rt_make_function_1(mp_builtin___repl_print__);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("abs"), true)->value = rt_make_function_1(mp_builtin_abs);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("all"), true)->value = rt_make_function_1(mp_builtin_all);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("any"), true)->value = rt_make_function_1(mp_builtin_any);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("bool"), true)->value = rt_make_function_var(0, mp_builtin_bool);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("callable"), true)->value = rt_make_function_1(mp_builtin_callable);
+#if MICROPY_ENABLE_FLOAT
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("complex"), true)->value = rt_make_function_var(0, mp_builtin_complex);
+#endif
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("chr"), true)->value = rt_make_function_1(mp_builtin_chr);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("dict"), true)->value = rt_make_function_0(mp_builtin_dict);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("divmod"), true)->value = rt_make_function_2(mp_builtin_divmod);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("hash"), true)->value = (mp_obj_t)&mp_builtin_hash_obj;
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("iter"), true)->value = (mp_obj_t)&mp_builtin_iter_obj;
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("len"), true)->value = rt_make_function_1(mp_builtin_len);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("list"), true)->value = rt_make_function_var(0, mp_builtin_list);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("max"), true)->value = rt_make_function_var(1, mp_builtin_max);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("min"), true)->value = rt_make_function_var(1, mp_builtin_min);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("next"), true)->value = (mp_obj_t)&mp_builtin_next_obj;
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("ord"), true)->value = rt_make_function_1(mp_builtin_ord);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("pow"), true)->value = rt_make_function_var(2, mp_builtin_pow);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("print"), true)->value = rt_make_function_var(0, mp_builtin_print);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("range"), true)->value = rt_make_function_var(1, mp_builtin_range);
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("set"), true)->value = (mp_obj_t)&mp_builtin_set_obj;
+    mp_qstr_map_lookup(&map_builtins, qstr_from_str_static("sum"), true)->value = rt_make_function_var(1, mp_builtin_sum);
 
     next_unique_code_id = 2; // 1 is reserved for the __main__ module scope
     unique_codes = NULL;
 
-    fun_str_join = rt_make_function_2(rt_str_join);
-    fun_str_format = rt_make_function_var(1, rt_str_format);
-    fun_list_append = rt_make_function_2(rt_list_append);
-    fun_list_pop = rt_make_function_2(rt_list_pop);
-    fun_list_sort = rt_make_function_2(rt_list_sort);
-    fun_gen_instance_next = rt_make_function_1(rt_gen_instance_next);
-
 #ifdef WRITE_CODE
     fp_write_code = fopen("out-code", "wb");
 #endif
@@ -359,9 +157,9 @@ int rt_get_unique_code_id(bool is_main_module) {
 
 static void alloc_unique_codes(void) {
     if (unique_codes == NULL) {
-        unique_codes = m_new(py_code_t, next_unique_code_id + 10); // XXX hack until we fix the REPL allocation problem
+        unique_codes = m_new(mp_code_t, next_unique_code_id + 10); // XXX hack until we fix the REPL allocation problem
         for (int i = 0; i < next_unique_code_id; i++) {
-            unique_codes[i].kind = PY_CODE_NONE;
+            unique_codes[i].kind = MP_CODE_NONE;
         }
     }
 }
@@ -370,7 +168,7 @@ void rt_assign_byte_code(int unique_code_id, byte *code, uint len, int n_args, i
     alloc_unique_codes();
 
     assert(unique_code_id < next_unique_code_id);
-    unique_codes[unique_code_id].kind = PY_CODE_BYTE;
+    unique_codes[unique_code_id].kind = MP_CODE_BYTE;
     unique_codes[unique_code_id].n_args = n_args;
     unique_codes[unique_code_id].n_locals = n_locals;
     unique_codes[unique_code_id].n_cells = n_cells;
@@ -390,8 +188,8 @@ void rt_assign_byte_code(int unique_code_id, byte *code, uint len, int n_args, i
         DEBUG_printf(" %02x", code[i]);
     }
     DEBUG_printf("\n");
-    extern void py_show_byte_code(const byte *code, int len);
-    py_show_byte_code(code, len);
+    extern void mp_show_byte_code(const byte *code, int len);
+    mp_show_byte_code(code, len);
 
 #ifdef WRITE_CODE
     if (fp_write_code != NULL) {
@@ -402,11 +200,11 @@ void rt_assign_byte_code(int unique_code_id, byte *code, uint len, int n_args, i
 #endif
 }
 
-void rt_assign_native_code(int unique_code_id, py_fun_t fun, uint len, int n_args) {
+void rt_assign_native_code(int unique_code_id, void *fun, uint len, int n_args) {
     alloc_unique_codes();
 
     assert(1 <= unique_code_id && unique_code_id < next_unique_code_id);
-    unique_codes[unique_code_id].kind = PY_CODE_NATIVE;
+    unique_codes[unique_code_id].kind = MP_CODE_NATIVE;
     unique_codes[unique_code_id].n_args = n_args;
     unique_codes[unique_code_id].n_locals = 0;
     unique_codes[unique_code_id].n_cells = 0;
@@ -436,11 +234,11 @@ void rt_assign_native_code(int unique_code_id, py_fun_t fun, uint len, int n_arg
 #endif
 }
 
-void rt_assign_inline_asm_code(int unique_code_id, py_fun_t fun, uint len, int n_args) {
+void rt_assign_inline_asm_code(int unique_code_id, void *fun, uint len, int n_args) {
     alloc_unique_codes();
 
     assert(1 <= unique_code_id && unique_code_id < next_unique_code_id);
-    unique_codes[unique_code_id].kind = PY_CODE_INLINE_ASM;
+    unique_codes[unique_code_id].kind = MP_CODE_INLINE_ASM;
     unique_codes[unique_code_id].n_args = n_args;
     unique_codes[unique_code_id].n_locals = 0;
     unique_codes[unique_code_id].n_cells = 0;
@@ -467,16 +265,52 @@ void rt_assign_inline_asm_code(int unique_code_id, py_fun_t fun, uint len, int n
 #endif
 }
 
+mp_map_t *rt_get_map_locals(void) {
+    return map_locals;
+}
+
+void rt_set_map_locals(mp_map_t *m) {
+    map_locals = m;
+}
+
+static bool fit_small_int(mp_small_int_t o) {
+    return true;
+}
+
+int rt_is_true(mp_obj_t arg) {
+    DEBUG_OP_printf("is true %p\n", arg);
+    if (MP_OBJ_IS_SMALL_INT(arg)) {
+        if (MP_OBJ_SMALL_INT_VALUE(arg) == 0) {
+            return 0;
+        } else {
+            return 1;
+        }
+    } else if (arg == mp_const_none) {
+        return 0;
+    } else if (arg == mp_const_false) {
+        return 0;
+    } else if (arg == mp_const_true) {
+        return 1;
+    } else {
+        assert(0);
+        return 0;
+    }
+}
+
+mp_obj_t rt_list_append(mp_obj_t self_in, mp_obj_t arg) {
+    return mp_obj_list_append(self_in, arg);
+}
+
 #define PARSE_DEC_IN_INTG (1)
 #define PARSE_DEC_IN_FRAC (2)
 #define PARSE_DEC_IN_EXP  (3)
 
-py_obj_t rt_load_const_dec(qstr qstr) {
+mp_obj_t rt_load_const_dec(qstr qstr) {
 #if MICROPY_ENABLE_FLOAT
     DEBUG_OP_printf("load '%s'\n", qstr_str(qstr));
     const char *s = qstr_str(qstr);
     int in = PARSE_DEC_IN_INTG;
-    py_float_t dec_val = 0;
+    mp_float_t dec_val = 0;
     bool exp_neg = false;
     int exp_val = 0;
     int exp_extra = 0;
@@ -513,7 +347,7 @@ py_obj_t rt_load_const_dec(qstr qstr) {
         }
     }
     if (*s != 0) {
-        nlr_jump(py_obj_new_exception_2(rt_q_SyntaxError, "invalid syntax for number", NULL, NULL));
+        nlr_jump(mp_obj_new_exception_msg(rt_q_SyntaxError, "invalid syntax for number"));
     }
     if (exp_neg) {
         exp_val = -exp_val;
@@ -526,52 +360,52 @@ py_obj_t rt_load_const_dec(qstr qstr) {
         dec_val *= 0.1;
     }
     if (imag) {
-        return py_obj_new_complex(0, dec_val);
+        return mp_obj_new_complex(0, dec_val);
     } else {
-        return py_obj_new_float(dec_val);
+        return mp_obj_new_float(dec_val);
     }
 #else
-    nlr_jump(py_obj_new_exception_2(rt_q_SyntaxError, "decimal numbers not supported", NULL, NULL));
+    nlr_jump(mp_obj_new_exception_msg(rt_q_SyntaxError, "decimal numbers not supported"));
 #endif
 }
 
-py_obj_t rt_load_const_str(qstr qstr) {
+mp_obj_t rt_load_const_str(qstr qstr) {
     DEBUG_OP_printf("load '%s'\n", qstr_str(qstr));
-    return py_obj_new_str(qstr);
+    return mp_obj_new_str(qstr);
 }
 
-py_obj_t rt_load_name(qstr qstr) {
+mp_obj_t rt_load_name(qstr qstr) {
     // logic: search locals, globals, builtins
     DEBUG_OP_printf("load name %s\n", qstr_str(qstr));
-    py_map_elem_t *elem = py_qstr_map_lookup(map_locals, qstr, false);
+    mp_map_elem_t *elem = mp_qstr_map_lookup(map_locals, qstr, false);
     if (elem == NULL) {
-        elem = py_qstr_map_lookup(map_globals, qstr, false);
+        elem = mp_qstr_map_lookup(map_globals, qstr, false);
         if (elem == NULL) {
-            elem = py_qstr_map_lookup(&map_builtins, qstr, false);
+            elem = mp_qstr_map_lookup(&map_builtins, qstr, false);
             if (elem == NULL) {
-                nlr_jump(py_obj_new_exception_2(rt_q_NameError, "name '%s' is not defined", qstr_str(qstr), NULL));
+                nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_NameError, "name '%s' is not defined", qstr_str(qstr)));
             }
         }
     }
     return elem->value;
 }
 
-py_obj_t rt_load_global(qstr qstr) {
+mp_obj_t rt_load_global(qstr qstr) {
     // logic: search globals, builtins
     DEBUG_OP_printf("load global %s\n", qstr_str(qstr));
-    py_map_elem_t *elem = py_qstr_map_lookup(map_globals, qstr, false);
+    mp_map_elem_t *elem = mp_qstr_map_lookup(map_globals, qstr, false);
     if (elem == NULL) {
-        elem = py_qstr_map_lookup(&map_builtins, qstr, false);
+        elem = mp_qstr_map_lookup(&map_builtins, qstr, false);
         if (elem == NULL) {
-            nlr_jump(py_obj_new_exception_2(rt_q_NameError, "name '%s' is not defined", qstr_str(qstr), NULL));
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_NameError, "name '%s' is not defined", qstr_str(qstr)));
         }
     }
     return elem->value;
 }
 
-py_obj_t rt_load_build_class(void) {
+mp_obj_t rt_load_build_class(void) {
     DEBUG_OP_printf("load_build_class\n");
-    py_map_elem_t *elem = py_qstr_map_lookup(&map_builtins, rt_q___build_class__, false);
+    mp_map_elem_t *elem = mp_qstr_map_lookup(&map_builtins, rt_q___build_class__, false);
     if (elem == NULL) {
         printf("name doesn't exist: __build_class__\n");
         assert(0);
@@ -579,97 +413,60 @@ py_obj_t rt_load_build_class(void) {
     return elem->value;
 }
 
-py_obj_t rt_new_cell(py_obj_t val) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_CELL;
-    o->u_cell = val;
-    return (py_obj_t)o;
-}
-
-py_obj_t rt_get_cell(py_obj_t cell) {
-    if (IS_O(cell, O_CELL)) {
-        return ((py_obj_base_t*)cell)->u_cell;
-    } else {
-        assert(0);
-        return py_const_none;
-    }
+mp_obj_t rt_get_cell(mp_obj_t cell) {
+    return mp_obj_cell_get(cell);
 }
 
-void rt_set_cell(py_obj_t cell, py_obj_t val) {
-    if (IS_O(cell, O_CELL)) {
-        ((py_obj_base_t*)cell)->u_cell = val;
-    } else {
-        assert(0);
-    }
+void rt_set_cell(mp_obj_t cell, mp_obj_t val) {
+    mp_obj_cell_set(cell, val);
 }
 
-void rt_store_name(qstr qstr, py_obj_t obj) {
+void rt_store_name(qstr qstr, mp_obj_t obj) {
     DEBUG_OP_printf("store name %s <- %p\n", qstr_str(qstr), obj);
-    py_qstr_map_lookup(map_locals, qstr, true)->value = obj;
+    mp_qstr_map_lookup(map_locals, qstr, true)->value = obj;
 }
 
-void rt_store_global(qstr qstr, py_obj_t obj) {
+void rt_store_global(qstr qstr, mp_obj_t obj) {
     DEBUG_OP_printf("store global %s <- %p\n", qstr_str(qstr), obj);
-    py_qstr_map_lookup(map_globals, qstr, true)->value = obj;
+    mp_qstr_map_lookup(map_globals, qstr, true)->value = obj;
 }
 
-py_obj_t rt_unary_op(int op, py_obj_t arg) {
+mp_obj_t rt_unary_op(int op, mp_obj_t arg) {
     DEBUG_OP_printf("unary %d %p\n", op, arg);
-    if (IS_SMALL_INT(arg)) {
-        py_small_int_t val = FROM_SMALL_INT(arg);
+    if (MP_OBJ_IS_SMALL_INT(arg)) {
+        mp_small_int_t val = MP_OBJ_SMALL_INT_VALUE(arg);
         switch (op) {
-            case RT_UNARY_OP_NOT: if (val != 0) { return py_const_true;} else { return py_const_false; }
+            case RT_UNARY_OP_NOT: if (val != 0) { return mp_const_true;} else { return mp_const_false; }
             case RT_UNARY_OP_POSITIVE: break;
             case RT_UNARY_OP_NEGATIVE: val = -val; break;
             case RT_UNARY_OP_INVERT: val = ~val; break;
             default: assert(0); val = 0;
         }
         if (fit_small_int(val)) {
-            return TO_SMALL_INT(val);
-        }
-#if MICROPY_ENABLE_FLOAT
-    } else if (IS_O(arg, O_FLOAT)) {
-        py_float_t val = py_obj_get_float(arg);
-        switch (op) {
-            case RT_UNARY_OP_NOT: if (val != 0) { return py_const_true;} else { return py_const_false; }
-            case RT_UNARY_OP_POSITIVE: break;
-            case RT_UNARY_OP_NEGATIVE: val = -val; break;
-            case RT_UNARY_OP_INVERT: nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "bad operand type for unary ~: 'float'", NULL, NULL));
-            default: assert(0); val = 0;
+            return MP_OBJ_NEW_SMALL_INT(val);
+        } else {
+            // TODO make a bignum
+            assert(0);
+            return mp_const_none;
+        }
+    } else { // will be an object (small ints are caught in previous if)
+        mp_obj_base_t *o = arg;
+        if (o->type->unary_op != NULL) {
+            mp_obj_t result = o->type->unary_op(op, arg);
+            if (result != NULL) {
+                return result;
+            }
         }
-        return py_obj_new_float(val);
-#endif
+        // TODO specify in error message what the operator is
+        nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "bad operand type for unary operator: '%s'", o->type->name));
     }
-    assert(0);
-    return py_const_none;
 }
 
-py_obj_t rt_binary_op(int op, py_obj_t lhs, py_obj_t rhs) {
+mp_obj_t rt_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
     DEBUG_OP_printf("binary %d %p %p\n", op, lhs, rhs);
-    if (op == RT_BINARY_OP_SUBSCR) {
-        if (IS_O(lhs, O_STR)) {
-            // string access
-            // XXX a hack!
-            const char *str = qstr_str(((py_obj_base_t*)lhs)->u_str);
-            return py_obj_new_int(str[FROM_SMALL_INT(rhs)]);
-        } else if ((IS_O(lhs, O_TUPLE) || IS_O(lhs, O_LIST))) {
-            // tuple/list load
-            uint index = get_index(lhs, rhs);
-            return ((py_obj_base_t*)lhs)->u_tuple_list.items[index];
-        } else if (IS_O(lhs, O_MAP)) {
-            // map load
-            py_map_elem_t *elem = py_map_lookup(lhs, rhs, false);
-            if (elem == NULL) {
-                nlr_jump(py_obj_new_exception_2(rt_q_KeyError, "<value>", NULL, NULL));
-            } else {
-                return elem->value;
-            }
-        } else {
-            assert(0);
-        }
-    } else if (IS_SMALL_INT(lhs) && IS_SMALL_INT(rhs)) {
-        py_small_int_t lhs_val = FROM_SMALL_INT(lhs);
-        py_small_int_t rhs_val = FROM_SMALL_INT(rhs);
+    if (MP_OBJ_IS_SMALL_INT(lhs) && MP_OBJ_IS_SMALL_INT(rhs)) {
+        mp_small_int_t lhs_val = MP_OBJ_SMALL_INT_VALUE(lhs);
+        mp_small_int_t rhs_val = MP_OBJ_SMALL_INT_VALUE(rhs);
         switch (op) {
             case RT_BINARY_OP_OR:
             case RT_BINARY_OP_INPLACE_OR: lhs_val |= rhs_val; break;
@@ -691,7 +488,7 @@ py_obj_t rt_binary_op(int op, py_obj_t lhs, py_obj_t rhs) {
             case RT_BINARY_OP_INPLACE_FLOOR_DIVIDE: lhs_val /= rhs_val; break;
 #if MICROPY_ENABLE_FLOAT
             case RT_BINARY_OP_TRUE_DIVIDE:
-            case RT_BINARY_OP_INPLACE_TRUE_DIVIDE: return py_obj_new_float((py_float_t)lhs_val / (py_float_t)rhs_val);
+            case RT_BINARY_OP_INPLACE_TRUE_DIVIDE: return mp_obj_new_float((mp_float_t)lhs_val / (mp_float_t)rhs_val);
 #endif
 
             // TODO implement modulo as specified by Python
@@ -717,102 +514,46 @@ py_obj_t rt_binary_op(int op, py_obj_t lhs, py_obj_t rhs) {
             default: printf("%d\n", op); assert(0);
         }
         if (fit_small_int(lhs_val)) {
-            return TO_SMALL_INT(lhs_val);
-        }
-#if MICROPY_ENABLE_FLOAT
-    } else if (IS_O(lhs, O_COMPLEX) || IS_O(rhs, O_COMPLEX)) {
-        py_float_t lhs_real, lhs_imag, rhs_real, rhs_imag;
-        py_obj_get_complex(lhs, &lhs_real, &lhs_imag);
-        py_obj_get_complex(rhs, &rhs_real, &rhs_imag);
-        switch (op) {
-            case RT_BINARY_OP_ADD:
-            case RT_BINARY_OP_INPLACE_ADD:
-                lhs_real += rhs_real;
-                lhs_imag += rhs_imag;
-                break;
-            case RT_BINARY_OP_SUBTRACT:
-            case RT_BINARY_OP_INPLACE_SUBTRACT:
-                lhs_real -= rhs_real;
-                lhs_imag -= rhs_imag;
-                break;
-            case RT_BINARY_OP_MULTIPLY:
-            case RT_BINARY_OP_INPLACE_MULTIPLY:
-            {
-                py_float_t real = lhs_real * rhs_real - lhs_imag * rhs_imag;
-                lhs_imag = lhs_real * rhs_imag + lhs_imag * rhs_real;
-                lhs_real = real;
-                break;
+            return MP_OBJ_NEW_SMALL_INT(lhs_val);
+        }
+    } else if (MP_OBJ_IS_OBJ(lhs)) {
+        mp_obj_base_t *o = lhs;
+        if (o->type->binary_op != NULL) {
+            mp_obj_t result = o->type->binary_op(op, lhs, rhs);
+            if (result != NULL) {
+                return result;
             }
-            /* TODO floor(?) the value
-            case RT_BINARY_OP_FLOOR_DIVIDE:
-            case RT_BINARY_OP_INPLACE_FLOOR_DIVIDE: val = lhs_val / rhs_val; break;
-            */
-            /* TODO
-            case RT_BINARY_OP_TRUE_DIVIDE:
-            case RT_BINARY_OP_INPLACE_TRUE_DIVIDE: val = lhs_val / rhs_val; break;
-            */
-            default: printf("%d\n", op); assert(0);
-        }
-        return py_obj_new_complex(lhs_real, lhs_imag);
-    } else if (IS_O(lhs, O_FLOAT) || IS_O(rhs, O_FLOAT)) {
-        py_float_t lhs_val = py_obj_get_float(lhs);
-        py_float_t rhs_val = py_obj_get_float(rhs);
-        switch (op) {
-            case RT_BINARY_OP_ADD:
-            case RT_BINARY_OP_INPLACE_ADD: lhs_val += rhs_val; break;
-            case RT_BINARY_OP_SUBTRACT:
-            case RT_BINARY_OP_INPLACE_SUBTRACT: lhs_val -= rhs_val; break;
-            case RT_BINARY_OP_MULTIPLY:
-            case RT_BINARY_OP_INPLACE_MULTIPLY: lhs_val *= rhs_val; break;
-            /* TODO floor(?) the value
-            case RT_BINARY_OP_FLOOR_DIVIDE:
-            case RT_BINARY_OP_INPLACE_FLOOR_DIVIDE: val = lhs_val / rhs_val; break;
-            */
-            case RT_BINARY_OP_TRUE_DIVIDE:
-            case RT_BINARY_OP_INPLACE_TRUE_DIVIDE: lhs_val /= rhs_val; break;
-            default: printf("%d\n", op); assert(0);
-        }
-        return py_obj_new_float(lhs_val);
-#endif
-    } else if (IS_O(lhs, O_STR) && IS_O(rhs, O_STR)) {
-        const char *lhs_str = qstr_str(((py_obj_base_t*)lhs)->u_str);
-        const char *rhs_str = qstr_str(((py_obj_base_t*)rhs)->u_str);
-        char *val;
-        switch (op) {
-            case RT_BINARY_OP_ADD:
-            case RT_BINARY_OP_INPLACE_ADD: val = m_new(char, strlen(lhs_str) + strlen(rhs_str) + 1); strcpy(val, lhs_str); strcat(val, rhs_str); break;
-            default: printf("%d\n", op); assert(0); val = NULL;
         }
-        return py_obj_new_str(qstr_from_str_take(val));
     }
-    assert(0);
-    return py_const_none;
+
+    // TODO specify in error message what the operator is
+    nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "unsupported operand type for binary operator: '%s'", mp_obj_get_type_str(lhs)));
 }
 
-py_obj_t rt_compare_op(int op, py_obj_t lhs, py_obj_t rhs) {
+mp_obj_t rt_compare_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
     DEBUG_OP_printf("compare %d %p %p\n", op, lhs, rhs);
 
     // deal with == and !=
     if (op == RT_COMPARE_OP_EQUAL || op == RT_COMPARE_OP_NOT_EQUAL) {
-        if (py_obj_equal(lhs, rhs)) {
+        if (mp_obj_equal(lhs, rhs)) {
             if (op == RT_COMPARE_OP_EQUAL) {
-                return py_const_true;
+                return mp_const_true;
             } else {
-                return py_const_false;
+                return mp_const_false;
             }
         } else {
             if (op == RT_COMPARE_OP_EQUAL) {
-                return py_const_false;
+                return mp_const_false;
             } else {
-                return py_const_true;
+                return mp_const_true;
             }
         }
     }
 
     // deal with small ints
-    if (IS_SMALL_INT(lhs) && IS_SMALL_INT(rhs)) {
-        py_small_int_t lhs_val = FROM_SMALL_INT(lhs);
-        py_small_int_t rhs_val = FROM_SMALL_INT(rhs);
+    if (MP_OBJ_IS_SMALL_INT(lhs) && MP_OBJ_IS_SMALL_INT(rhs)) {
+        mp_small_int_t lhs_val = MP_OBJ_SMALL_INT_VALUE(lhs);
+        mp_small_int_t rhs_val = MP_OBJ_SMALL_INT_VALUE(rhs);
         int cmp;
         switch (op) {
             case RT_COMPARE_OP_LESS: cmp = lhs_val < rhs_val; break;
@@ -822,17 +563,17 @@ py_obj_t rt_compare_op(int op, py_obj_t lhs, py_obj_t rhs) {
             default: assert(0); cmp = 0;
         }
         if (cmp) {
-            return py_const_true;
+            return mp_const_true;
         } else {
-            return py_const_false;
+            return mp_const_false;
         }
     }
 
 #if MICROPY_ENABLE_FLOAT
     // deal with floats
-    if (IS_O(lhs, O_FLOAT) || IS_O(rhs, O_FLOAT)) {
-        py_float_t lhs_val = py_obj_get_float(lhs);
-        py_float_t rhs_val = py_obj_get_float(rhs);
+    if (MP_OBJ_IS_TYPE(lhs, &float_type) || MP_OBJ_IS_TYPE(rhs, &float_type)) {
+        mp_float_t lhs_val = mp_obj_get_float(lhs);
+        mp_float_t rhs_val = mp_obj_get_float(rhs);
         int cmp;
         switch (op) {
             case RT_COMPARE_OP_LESS: cmp = lhs_val < rhs_val; break;
@@ -842,666 +583,287 @@ py_obj_t rt_compare_op(int op, py_obj_t lhs, py_obj_t rhs) {
             default: assert(0); cmp = 0;
         }
         if (cmp) {
-            return py_const_true;
+            return mp_const_true;
         } else {
-            return py_const_false;
+            return mp_const_false;
         }
     }
 #endif
 
     // not implemented
     assert(0);
-    return py_const_none;
+    return mp_const_none;
 }
 
-py_obj_t rt_make_function_from_id(int unique_code_id) {
+mp_obj_t rt_make_function_from_id(int unique_code_id) {
     DEBUG_OP_printf("make_function_from_id %d\n", unique_code_id);
     if (unique_code_id < 1 || unique_code_id >= next_unique_code_id) {
         // illegal code id
-        return py_const_none;
+        return mp_const_none;
     }
-    py_code_t *c = &unique_codes[unique_code_id];
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
+
+    // make the function, depending on the code kind
+    mp_code_t *c = &unique_codes[unique_code_id];
+    mp_obj_t fun;
     switch (c->kind) {
-        case PY_CODE_BYTE:
-            o->kind = O_FUN_BC;
-            o->u_fun_bc.n_args = c->n_args;
-            o->u_fun_bc.n_state = c->n_locals + c->n_cells + c->n_stack;
-            o->u_fun_bc.code = c->u_byte.code;
+        case MP_CODE_BYTE:
+            fun = mp_obj_new_fun_bc(c->n_args, c->n_locals + c->n_cells + c->n_stack, c->u_byte.code);
             break;
-        case PY_CODE_NATIVE:
+        case MP_CODE_NATIVE:
             switch (c->n_args) {
-                case 0: o->kind = O_FUN_0; break;
-                case 1: o->kind = O_FUN_1; break;
-                case 2: o->kind = O_FUN_2; break;
-                default: assert(0);
+                case 0: fun = rt_make_function_0(c->u_native.fun); break;
+                case 1: fun = rt_make_function_1((mp_fun_1_t)c->u_native.fun); break;
+                case 2: fun = rt_make_function_2((mp_fun_2_t)c->u_native.fun); break;
+                default: assert(0); fun = mp_const_none;
             }
-            o->u_fun.fun = c->u_native.fun;
             break;
-        case PY_CODE_INLINE_ASM:
-            o->kind = O_FUN_ASM;
-            o->u_fun_asm.n_args = c->n_args;
-            o->u_fun_asm.fun = c->u_inline_asm.fun;
+        case MP_CODE_INLINE_ASM:
+            fun = mp_obj_new_fun_asm(c->n_args, c->u_inline_asm.fun);
             break;
         default:
             assert(0);
+            fun = mp_const_none;
     }
 
     // check for generator functions and if so wrap in generator object
     if (c->is_generator) {
-        py_obj_base_t *o2 = m_new(py_obj_base_t, 1);
-        o2->kind = O_GEN_WRAP;
-        // we have at least 3 locals so the bc can write back fast[0,1,2] safely; should improve how this is done
-        o2->u_gen_wrap.n_state = ((c->n_locals + c->n_cells) < 3 ? 3 : (c->n_locals + c->n_cells)) + c->n_stack;
-        o2->u_gen_wrap.fun = o;
-        o = o2;
+        fun = mp_obj_new_gen_wrap(c->n_locals, c->n_cells, c->n_stack, fun);
     }
 
-    return o;
-}
-
-py_obj_t rt_make_function_0(py_fun_0_t fun) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_FUN_0;
-    o->u_fun.fun = fun;
-    return o;
+    return fun;
 }
 
-py_obj_t rt_make_function_1(py_fun_1_t fun) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_FUN_1;
-    o->u_fun.fun = fun;
-    return o;
-}
-
-py_obj_t rt_make_function_2(py_fun_2_t fun) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_FUN_2;
-    o->u_fun.fun = fun;
-    return o;
-}
-
-py_obj_t rt_make_function(int n_args, py_fun_t code) {
-    // assumes code is a pointer to a py_fun_t (i think this is safe...)
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_FUN_N;
-    o->u_fun.n_args = n_args;
-    o->u_fun.fun = code;
-    return o;
-}
-
-py_obj_t rt_make_function_var(int n_fixed_args, py_fun_var_t f) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_FUN_VAR;
-    o->u_fun.n_args = n_fixed_args;
-    o->u_fun.fun = f;
-    return o;
-}
-
-py_obj_t rt_make_closure_from_id(int unique_code_id, py_obj_t closure_tuple) {
-    py_obj_t f = rt_make_function_from_id(unique_code_id);
+mp_obj_t rt_make_closure_from_id(int unique_code_id, mp_obj_t closure_tuple) {
+    // make function object
+    mp_obj_t ffun = rt_make_function_from_id(unique_code_id);
     // wrap function in closure object
-    py_obj_base_t *f2 = m_new(py_obj_base_t, 1);
-    f2->kind = O_CLOSURE;
-    f2->u_closure.fun = f;
-    f2->u_closure.vars = closure_tuple;
-    return f2;
+    return mp_obj_new_closure(ffun, closure_tuple);
 }
 
-py_obj_t rt_call_function_0(py_obj_t fun) {
+mp_obj_t rt_call_function_0(mp_obj_t fun) {
     return rt_call_function_n(fun, 0, NULL);
 }
 
-py_obj_t rt_call_function_1(py_obj_t fun, py_obj_t arg) {
+mp_obj_t rt_call_function_1(mp_obj_t fun, mp_obj_t arg) {
     return rt_call_function_n(fun, 1, &arg);
 }
 
-py_obj_t rt_call_function_2(py_obj_t fun, py_obj_t arg1, py_obj_t arg2) {
-    py_obj_t args[2];
+mp_obj_t rt_call_function_2(mp_obj_t fun, mp_obj_t arg1, mp_obj_t arg2) {
+    mp_obj_t args[2];
     args[1] = arg1;
     args[0] = arg2;
     return rt_call_function_n(fun, 2, args);
 }
 
-typedef machine_uint_t (*inline_asm_fun_0_t)();
-typedef machine_uint_t (*inline_asm_fun_1_t)(machine_uint_t);
-typedef machine_uint_t (*inline_asm_fun_2_t)(machine_uint_t, machine_uint_t);
-typedef machine_uint_t (*inline_asm_fun_3_t)(machine_uint_t, machine_uint_t, machine_uint_t);
-
-// convert a Python object to a sensible value for inline asm
-machine_uint_t rt_convert_obj_for_inline_asm(py_obj_t obj) {
-    // TODO for byte_array, pass pointer to the array
-    if (IS_SMALL_INT(obj)) {
-        return FROM_SMALL_INT(obj);
-    } else if (obj == py_const_none) {
-        return 0;
-    } else if (obj == py_const_false) {
-        return 0;
-    } else if (obj == py_const_true) {
-        return 1;
-    } else {
-        py_obj_base_t *o = obj;
-        switch (o->kind) {
-            case O_STR:
-                // pointer to the string (it's probably constant though!)
-                return (machine_uint_t)qstr_str(o->u_str);
-
-#if MICROPY_ENABLE_FLOAT
-            case O_FLOAT:
-                // convert float to int (could also pass in float registers)
-                return (machine_int_t)o->u_float;
-#endif
-
-            case O_TUPLE:
-            case O_LIST:
-                // pointer to start of tuple/list (could pass length, but then could use len(x) for that)
-                return (machine_uint_t)o->u_tuple_list.items;
-
-            default:
-                // just pass along a pointer to the object
-                return (machine_uint_t)obj;
-        }
-    }
-}
-
-// convert a return value from inline asm to a sensible Python object
-py_obj_t rt_convert_val_from_inline_asm(machine_uint_t val) {
-    return TO_SMALL_INT(val);
-}
-
 // args are in reverse order in the array
-py_obj_t rt_call_function_n(py_obj_t fun, int n_args, const py_obj_t *args) {
-    int n_args_fun = 0;
-    if (IS_O(fun, O_FUN_0)) {
-        py_obj_base_t *o = fun;
-        if (n_args != 0) {
-            n_args_fun = 0;
-            goto bad_n_args;
-        }
-        DEBUG_OP_printf("calling native %p()\n", o->u_fun.fun);
-        return ((py_fun_0_t)o->u_fun.fun)();
-
-    } else if (IS_O(fun, O_FUN_1)) {
-        py_obj_base_t *o = fun;
-        if (n_args != 1) {
-            n_args_fun = 1;
-            goto bad_n_args;
-        }
-        DEBUG_OP_printf("calling native %p(%p)\n", o->u_fun.fun, args[0]);
-        return ((py_fun_1_t)o->u_fun.fun)(args[0]);
-
-    } else if (IS_O(fun, O_FUN_2)) {
-        py_obj_base_t *o = fun;
-        if (n_args != 2) {
-            n_args_fun = 2;
-            goto bad_n_args;
-        }
-        DEBUG_OP_printf("calling native %p(%p, %p)\n", o->u_fun.fun, args[1], args[0]);
-        return ((py_fun_2_t)o->u_fun.fun)(args[1], args[0]);
-
-    // TODO O_FUN_N
-
-    } else if (IS_O(fun, O_FUN_VAR)) {
-        py_obj_base_t *o = fun;
-        if (n_args < o->u_fun.n_args) {
-            nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "<fun name>() missing %d required positional arguments: <list of names of params>", (const char*)(machine_int_t)(o->u_fun.n_args - n_args), NULL));
-        }
-        // TODO really the args need to be passed in as a Python tuple, as the form f(*[1,2]) can be used to pass var args
-        py_obj_t *args_ordered = m_new(py_obj_t, n_args);
-        for (int i = 0; i < n_args; i++) {
-            args_ordered[i] = args[n_args - i - 1];
-        }
-        py_obj_t res = ((py_fun_var_t)o->u_fun.fun)(n_args, args_ordered);
-        m_free(args_ordered);
-        return res;
-
-    } else if (IS_O(fun, O_FUN_BC)) {
-        py_obj_base_t *o = fun;
-        if (n_args != o->u_fun_bc.n_args) {
-            n_args_fun = o->u_fun_bc.n_args;
-            goto bad_n_args;
-        }
-        DEBUG_OP_printf("calling byte code %p(n_args=%d)\n", o->u_fun_bc.code, n_args);
-        return py_execute_byte_code(o->u_fun_bc.code, args, n_args, o->u_fun_bc.n_state);
-
-    } else if (IS_O(fun, O_FUN_ASM)) {
-        py_obj_base_t *o = fun;
-        if (n_args != o->u_fun_asm.n_args) {
-            n_args_fun = o->u_fun_asm.n_args;
-            goto bad_n_args;
-        }
-        DEBUG_OP_printf("calling inline asm %p(n_args=%d)\n", o->u_fun_asm.fun, n_args);
-        machine_uint_t ret;
-        if (n_args == 0) {
-            ret = ((inline_asm_fun_0_t)o->u_fun_asm.fun)();
-        } else if (n_args == 1) {
-            ret = ((inline_asm_fun_1_t)o->u_fun_asm.fun)(rt_convert_obj_for_inline_asm(args[0]));
-        } else if (n_args == 2) {
-            ret = ((inline_asm_fun_2_t)o->u_fun_asm.fun)(rt_convert_obj_for_inline_asm(args[1]), rt_convert_obj_for_inline_asm(args[0]));
-        } else if (n_args == 3) {
-            ret = ((inline_asm_fun_3_t)o->u_fun_asm.fun)(rt_convert_obj_for_inline_asm(args[2]), rt_convert_obj_for_inline_asm(args[1]), rt_convert_obj_for_inline_asm(args[0]));
-        } else {
-            assert(0);
-            ret = 0;
-        }
-        return rt_convert_val_from_inline_asm(ret);
-
-    } else if (IS_O(fun, O_GEN_WRAP)) {
-        py_obj_base_t *o = fun;
-        py_obj_base_t *o_fun = o->u_gen_wrap.fun;
-        assert(o_fun->kind == O_FUN_BC); // TODO
-        if (n_args != o_fun->u_fun_bc.n_args) {
-            n_args_fun = o_fun->u_fun_bc.n_args;
-            goto bad_n_args;
-        }
-        py_obj_t *state = m_new(py_obj_t, 1 + o->u_gen_wrap.n_state);
-        // put function object at first slot in state (to keep u_gen_instance small)
-        state[0] = o_fun;
-        // init args
-        for (int i = 0; i < n_args; i++) {
-            state[1 + i] = args[n_args - 1 - i];
-        }
-        py_obj_base_t *o2 = m_new(py_obj_base_t, 1);
-        o2->kind = O_GEN_INSTANCE;
-        o2->u_gen_instance.state = state;
-        o2->u_gen_instance.ip = o_fun->u_fun_bc.code;
-        o2->u_gen_instance.sp = state + o->u_gen_wrap.n_state;
-        return o2;
-
-    } else if (IS_O(fun, O_BOUND_METH)) {
-        py_obj_base_t *o = fun;
-        DEBUG_OP_printf("calling bound method %p(self=%p, n_args=%d)\n", o->u_bound_meth.meth, o->u_bound_meth.self, n_args);
-        if (n_args == 0) {
-            return rt_call_function_n(o->u_bound_meth.meth, 1, &o->u_bound_meth.self);
-        } else if (n_args == 1) {
-            py_obj_t args2[2];
-            args2[1] = o->u_bound_meth.self;
-            args2[0] = args[0];
-            return rt_call_function_n(o->u_bound_meth.meth, 2, args2);
-        } else {
-            // TODO not implemented
-            assert(0);
-            return py_const_none;
-            //return rt_call_function_2(o->u_bound_meth.meth, n_args + 1, o->u_bound_meth.self + args);
-        }
+mp_obj_t rt_call_function_n(mp_obj_t fun_in, int n_args, const mp_obj_t *args) {
+    // TODO improve this: fun object can specify its type and we parse here the arguments,
+    // passing to the function arrays of fixed and keyword arguments
 
-    } else if (IS_O(fun, O_CLASS)) {
-        // instantiate an instance of a class
-
-        DEBUG_OP_printf("instantiate object of class %p with %d args\n", fun, n_args);
-        py_obj_base_t *o = m_new(py_obj_base_t, 1);
-        o->kind = O_OBJ;
-        o->u_obj.class = fun;
-        o->u_obj.members = py_map_new(MAP_QSTR, 0);
-
-        // look for __init__ function
-        py_obj_base_t *o_class = fun;
-        py_map_elem_t *init_fn = py_qstr_map_lookup(o_class->u_class.locals, qstr_from_str_static("__init__"), false);
-
-        if (init_fn != NULL) {
-            // call __init__ function
-            py_obj_t init_ret;
-            if (n_args == 0) {
-                init_ret = rt_call_function_n(init_fn->value, 1, (py_obj_t*)&o);
-            } else {
-                py_obj_t *args2 = m_new(py_obj_t, n_args + 1);
-                memcpy(args2, args, n_args * sizeof(py_obj_t));
-                args2[n_args] = o;
-                init_ret = rt_call_function_n(init_fn->value, n_args + 1, args2);
-                m_free(args2);
-            }
-            if (init_ret != py_const_none) {
-                nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "__init__() should return None, not '%s'", py_obj_get_type_str(init_ret), NULL));
-            }
+    DEBUG_OP_printf("calling function %p(n_args=%d, args=%p)\n", fun_in, n_args, args);
 
+    if (MP_OBJ_IS_SMALL_INT(fun_in)) {
+        nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "'int' object is not callable"));
+    } else {
+        mp_obj_base_t *fun = fun_in;
+        if (fun->type->call_n != NULL) {
+            return fun->type->call_n(fun_in, n_args, args);
         } else {
-            // TODO
-            if (n_args != 0) {
-                n_args_fun = 0;
-                goto bad_n_args;
-            }
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "'%s' object is not callable", fun->type->name));
         }
-
-        return o;
-
-    } else {
-        printf("fun %p %d\n", fun, ((py_obj_base_t*)fun)->kind);
-        assert(0);
-        return py_const_none;
     }
-
-bad_n_args:
-    nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "function takes %d positional arguments but %d were given", (const char*)(machine_int_t)n_args_fun, (const char*)(machine_int_t)n_args));
 }
 
 // args are in reverse order in the array; keyword arguments come first, value then key
 // eg: (value1, key1, value0, key0, arg1, arg0)
-py_obj_t rt_call_function_n_kw(py_obj_t fun, uint n_args, uint n_kw, const py_obj_t *args) {
+mp_obj_t rt_call_function_n_kw(mp_obj_t fun, uint n_args, uint n_kw, const mp_obj_t *args) {
     // TODO
     assert(0);
-    return py_const_none;
+    return mp_const_none;
 }
 
 // args contains: arg(n_args-1)  arg(n_args-2)  ...  arg(0)  self/NULL  fun
 // if n_args==0 then there are only self/NULL and fun
-py_obj_t rt_call_method_n(uint n_args, const py_obj_t *args) {
+mp_obj_t rt_call_method_n(uint n_args, const mp_obj_t *args) {
     DEBUG_OP_printf("call method %p(self=%p, n_args=%u)\n", args[n_args + 1], args[n_args], n_args);
     return rt_call_function_n(args[n_args + 1], n_args + ((args[n_args] == NULL) ? 0 : 1), args);
 }
 
 // args contains: kw_val(n_kw-1)  kw_key(n_kw-1) ... kw_val(0)  kw_key(0)  arg(n_args-1)  arg(n_args-2)  ...  arg(0)  self/NULL  fun
-py_obj_t rt_call_method_n_kw(uint n_args, uint n_kw, const py_obj_t *args) {
+mp_obj_t rt_call_method_n_kw(uint n_args, uint n_kw, const mp_obj_t *args) {
     uint n = n_args + 2 * n_kw;
     DEBUG_OP_printf("call method %p(self=%p, n_args=%u, n_kw=%u)\n", args[n + 1], args[n], n_args, n_kw);
     return rt_call_function_n_kw(args[n + 1], n_args + ((args[n] == NULL) ? 0 : 1), n_kw, args);
 }
 
 // items are in reverse order
-py_obj_t rt_build_tuple(int n_args, py_obj_t *items) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_TUPLE;
-    o->u_tuple_list.alloc = n_args < 4 ? 4 : n_args;
-    o->u_tuple_list.len = n_args;
-    o->u_tuple_list.items = m_new(py_obj_t, o->u_tuple_list.alloc);
-    for (int i = 0; i < n_args; i++) {
-        o->u_tuple_list.items[i] = items[n_args - i - 1];
-    }
-    return o;
+mp_obj_t rt_build_tuple(int n_args, mp_obj_t *items) {
+    return mp_obj_new_tuple_reverse(n_args, items);
 }
 
 // items are in reverse order
-py_obj_t rt_build_list(int n_args, py_obj_t *items) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_LIST;
-    o->u_tuple_list.alloc = n_args < 4 ? 4 : n_args;
-    o->u_tuple_list.len = n_args;
-    o->u_tuple_list.items = m_new(py_obj_t, o->u_tuple_list.alloc);
-    for (int i = 0; i < n_args; i++) {
-        o->u_tuple_list.items[i] = items[n_args - i - 1];
-    }
-    return o;
+mp_obj_t rt_build_list(int n_args, mp_obj_t *items) {
+    return mp_obj_new_list_reverse(n_args, items);
 }
 
-py_obj_t rt_build_set(int n_args, py_obj_t *items) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_SET;
-    o->u_set.alloc = get_doubling_prime_greater_or_equal_to(n_args + 1);
-    o->u_set.used = 0;
-    o->u_set.table = m_new(py_obj_t, o->u_set.alloc);
-    for (int i = 0; i < o->u_set.alloc; i++) {
-        o->u_set.table[i] = NULL;
-    }
-    for (int i = 0; i < n_args; i++) {
-        py_set_lookup(o, items[i], true);
-    }
-    return o;
+mp_obj_t rt_build_set(int n_args, mp_obj_t *items) {
+    return mp_obj_new_set(n_args, items);
 }
 
-py_obj_t rt_store_set(py_obj_t set, py_obj_t item) {
-    py_set_lookup(set, item, true);
+mp_obj_t rt_store_set(mp_obj_t set, mp_obj_t item) {
+    mp_set_lookup(set, item, true);
     return set;
 }
 
 // unpacked items are stored in order into the array pointed to by items
-void rt_unpack_sequence(py_obj_t seq_in, uint num, py_obj_t *items) {
-    if (IS_O(seq_in, O_TUPLE) || IS_O(seq_in, O_LIST)) {
-        py_obj_base_t *seq = seq_in;
-        if (seq->u_tuple_list.len < num) {
-            nlr_jump(py_obj_new_exception_2(rt_q_ValueError, "need more than %d values to unpack", (void*)seq->u_tuple_list.len, NULL));
-        } else if (seq->u_tuple_list.len > num) {
-            nlr_jump(py_obj_new_exception_2(rt_q_ValueError, "too many values to unpack (expected %d)", (void*)(machine_uint_t)num, NULL));
+void rt_unpack_sequence(mp_obj_t seq_in, uint num, mp_obj_t *items) {
+    if (MP_OBJ_IS_TYPE(seq_in, &tuple_type) || MP_OBJ_IS_TYPE(seq_in, &list_type)) {
+        uint seq_len;
+        mp_obj_t *seq_items;
+        if (MP_OBJ_IS_TYPE(seq_in, &tuple_type)) {
+            mp_obj_tuple_get(seq_in, &seq_len, &seq_items);
+        } else {
+            mp_obj_list_get(seq_in, &seq_len, &seq_items);
         }
-        memcpy(items, seq->u_tuple_list.items, num * sizeof(py_obj_t));
+        if (seq_len < num) {
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_ValueError, "need more than %d values to unpack", (void*)(machine_uint_t)seq_len));
+        } else if (seq_len > num) {
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_ValueError, "too many values to unpack (expected %d)", (void*)(machine_uint_t)num));
+        }
+        memcpy(items, seq_items, num * sizeof(mp_obj_t));
     } else {
         // TODO call rt_getiter and extract via rt_iternext
-        nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "'%s' object is not iterable", py_obj_get_type_str(seq_in), NULL));
+        nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "'%s' object is not iterable", mp_obj_get_type_str(seq_in)));
     }
 }
 
-py_obj_t rt_build_map(int n_args) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_MAP;
-    py_map_init(&o->u_map, MAP_PY_OBJ, n_args);
-    return o;
-}
-
-py_obj_t rt_store_map(py_obj_t map, py_obj_t key, py_obj_t value) {
-    assert(IS_O(map, O_MAP)); // should always be
-    py_map_lookup(map, key, true)->value = value;
-    return map;
+mp_obj_t rt_build_map(int n_args) {
+    return mp_obj_new_dict(n_args);
 }
 
-py_obj_t build_bound_method(py_obj_t self, py_obj_t meth) {
-    py_obj_base_t *o = m_new(py_obj_base_t, 1);
-    o->kind = O_BOUND_METH;
-    o->u_bound_meth.meth = meth;
-    o->u_bound_meth.self = self;
-    return o;
+mp_obj_t rt_store_map(mp_obj_t map, mp_obj_t key, mp_obj_t value) {
+    // map should always be a dict
+    return mp_obj_dict_store(map, key, value);
 }
 
-py_obj_t rt_load_attr(py_obj_t base, qstr attr) {
+mp_obj_t rt_load_attr(mp_obj_t base, qstr attr) {
     DEBUG_OP_printf("load attr %s\n", qstr_str(attr));
-    if (IS_O(base, O_LIST) && attr == rt_q_append) {
-        return build_bound_method(base, fun_list_append);
-    } else if (IS_O(base, O_LIST) && attr == rt_q_pop) {
-        return build_bound_method(base, fun_list_pop);
-    } else if (IS_O(base, O_LIST) && attr == rt_q_sort) {
-        return build_bound_method(base, fun_list_sort);
-    } else if (IS_O(base, O_CLASS)) {
-        py_obj_base_t *o = base;
-        py_map_elem_t *elem = py_qstr_map_lookup(o->u_class.locals, attr, false);
+    if (MP_OBJ_IS_TYPE(base, &class_type)) {
+        mp_map_elem_t *elem = mp_qstr_map_lookup(mp_obj_class_get_locals(base), attr, false);
         if (elem == NULL) {
-            goto no_attr;
+            nlr_jump(mp_obj_new_exception_msg_2_args(rt_q_AttributeError, "'%s' object has no attribute '%s'", mp_obj_get_type_str(base), qstr_str(attr)));
         }
         return elem->value;
-    } else if (IS_O(base, O_OBJ)) {
-        // logic: look in obj members then class locals (TODO check this against CPython)
-        py_obj_base_t *o = base;
-        py_map_elem_t *elem = py_qstr_map_lookup(o->u_obj.members, attr, false);
-        if (elem != NULL) {
-            // object member, always treated as a value
-            return elem->value;
-        }
-        elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, false);
-        if (elem != NULL) {
-            if (py_obj_is_callable(elem->value)) {
-                // class member is callable so build a bound method
-                return build_bound_method(base, elem->value);
-            } else {
-                // class member is a value, so just return that value
-                return elem->value;
+    } else if (MP_OBJ_IS_TYPE(base, &instance_type)) {
+        return mp_obj_instance_load_attr(base, attr);
+    } else if (MP_OBJ_IS_OBJ(base)) {
+        // generic method lookup
+        mp_obj_base_t *o = base;
+        const mp_method_t *meth = &o->type->methods[0];
+        for (; meth->name != NULL; meth++) {
+            if (strcmp(meth->name, qstr_str(attr)) == 0) {
+                return mp_obj_new_bound_meth(base, (mp_obj_t)meth->fun);
             }
         }
-        goto no_attr;
     }
-
-no_attr:
-    nlr_jump(py_obj_new_exception_2(rt_q_AttributeError, "'%s' object has no attribute '%s'", py_obj_get_type_str(base), qstr_str(attr)));
+    nlr_jump(mp_obj_new_exception_msg_2_args(rt_q_AttributeError, "'%s' object has no attribute '%s'", mp_obj_get_type_str(base), qstr_str(attr)));
 }
 
-void rt_load_method(py_obj_t base, qstr attr, py_obj_t *dest) {
+void rt_load_method(mp_obj_t base, qstr attr, mp_obj_t *dest) {
     DEBUG_OP_printf("load method %s\n", qstr_str(attr));
-    if (IS_O(base, O_STR)) {
-        if (attr == rt_q_join) {
-            dest[1] = fun_str_join;
-            dest[0] = base;
-            return;
-        } else if (attr == rt_q_format) {
-            dest[1] = fun_str_format;
-            dest[0] = base;
-            return;
-        }
-    } else if (IS_O(base, O_GEN_INSTANCE) && attr == rt_q___next__) {
-        dest[1] = fun_gen_instance_next;
-        dest[0] = base;
-        return;
-    } else if (IS_O(base, O_LIST) && attr == rt_q_append) {
-        dest[1] = fun_list_append;
-        dest[0] = base;
-        return;
-    } else if (IS_O(base, O_LIST) && attr == rt_q_pop) {
-        dest[1] = fun_list_pop;
+    if (MP_OBJ_IS_TYPE(base, &gen_instance_type) && attr == rt_q___next__) {
+        dest[1] = (mp_obj_t)&mp_obj_gen_instance_next_obj;
         dest[0] = base;
         return;
-    } else if (IS_O(base, O_LIST) && attr == rt_q_sort) {
-        dest[1] = fun_list_sort;
-        dest[0] = base;
+    } else if (MP_OBJ_IS_TYPE(base, &instance_type)) {
+        mp_obj_instance_load_method(base, attr, dest);
         return;
-    } else if (IS_O(base, O_OBJ)) {
-        // logic: look in obj members then class locals (TODO check this against CPython)
-        py_obj_base_t *o = base;
-        py_map_elem_t *elem = py_qstr_map_lookup(o->u_obj.members, attr, false);
-        if (elem != NULL) {
-            // object member, always treated as a value
-            dest[1] = elem->value;
-            dest[0] = NULL;
-            return;
-        }
-        elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, false);
-        if (elem != NULL) {
-            if (py_obj_is_callable(elem->value)) {
-                // class member is callable so build a bound method
-                dest[1] = elem->value;
-                dest[0] = base;
-                return;
-            } else {
-                // class member is a value, so just return that value
-                dest[1] = elem->value;
-                dest[0] = NULL;
-                return;
-            }
-        }
-        goto no_attr;
-    } else if (IS_O(base, O_USER)) {
-        py_obj_base_t *o = base;
-        const py_user_method_t *meth = &o->u_user.info->methods[0];
+    } else if (MP_OBJ_IS_OBJ(base)) {
+        // generic method lookup
+        mp_obj_base_t *o = base;
+        const mp_method_t *meth = &o->type->methods[0];
         for (; meth->name != NULL; meth++) {
             if (strcmp(meth->name, qstr_str(attr)) == 0) {
-                if (meth->kind == 0) {
-                    dest[1] = rt_make_function_1(meth->fun);
-                } else if (meth->kind == 1) {
-                    dest[1] = rt_make_function_2(meth->fun);
-                } else {
-                    assert(0);
-                }
+                dest[1] = (mp_obj_t)meth->fun;
                 dest[0] = base;
                 return;
             }
         }
     }
 
-no_attr:
+    // no method; fallback to load_attr
     dest[1] = rt_load_attr(base, attr);
     dest[0] = NULL;
 }
 
-void rt_store_attr(py_obj_t base, qstr attr, py_obj_t value) {
+void rt_store_attr(mp_obj_t base, qstr attr, mp_obj_t value) {
     DEBUG_OP_printf("store attr %p.%s <- %p\n", base, qstr_str(attr), value);
-    if (IS_O(base, O_CLASS)) {
+    if (MP_OBJ_IS_TYPE(base, &class_type)) {
         // TODO CPython allows STORE_ATTR to a class, but is this the correct implementation?
-        py_obj_base_t *o = base;
-        py_qstr_map_lookup(o->u_class.locals, attr, true)->value = value;
-    } else if (IS_O(base, O_OBJ)) {
-        // logic: look in class locals (no add) then obj members (add) (TODO check this against CPython)
-        py_obj_base_t *o = base;
-        py_map_elem_t *elem = py_qstr_map_lookup(o->u_obj.class->u_class.locals, attr, false);
-        if (elem != NULL) {
-            elem->value = value;
-        } else {
-            py_qstr_map_lookup(o->u_obj.members, attr, true)->value = value;
-        }
+        mp_map_t *locals = mp_obj_class_get_locals(base);
+        mp_qstr_map_lookup(locals, attr, true)->value = value;
+    } else if (MP_OBJ_IS_TYPE(base, &instance_type)) {
+        mp_obj_instance_store_attr(base, attr, value);
     } else {
-        printf("?AttributeError: '%s' object has no attribute '%s'\n", py_obj_get_type_str(base), qstr_str(attr));
+        printf("?AttributeError: '%s' object has no attribute '%s'\n", mp_obj_get_type_str(base), qstr_str(attr));
         assert(0);
     }
 }
 
-void rt_store_subscr(py_obj_t base, py_obj_t index, py_obj_t value) {
+void rt_store_subscr(mp_obj_t base, mp_obj_t index, mp_obj_t value) {
     DEBUG_OP_printf("store subscr %p[%p] <- %p\n", base, index, value);
-    if (IS_O(base, O_LIST)) {
+    if (MP_OBJ_IS_TYPE(base, &list_type)) {
         // list store
-        uint i = get_index(base, index);
-        ((py_obj_base_t*)base)->u_tuple_list.items[i] = value;
-    } else if (IS_O(base, O_MAP)) {
-        // map store
-        py_map_lookup(base, index, true)->value = value;
+        mp_obj_list_store(base, index, value);
+    } else if (MP_OBJ_IS_TYPE(base, &dict_type)) {
+        // dict store
+        mp_obj_dict_store(base, index, value);
     } else {
         assert(0);
     }
 }
 
-py_obj_t rt_getiter(py_obj_t o_in) {
-    if (IS_O(o_in, O_GEN_INSTANCE)) {
-        return o_in;
-    } else if (IS_O(o_in, O_RANGE)) {
-        py_obj_base_t *o = o_in;
-        return py_obj_new_range_iterator(o->u_range.start, o->u_range.stop, o->u_range.step);
-    } else if (IS_O(o_in, O_TUPLE)) {
-        return py_obj_new_tuple_iterator(o_in, 0);
-    } else if (IS_O(o_in, O_LIST)) {
-        return py_obj_new_list_iterator(o_in, 0);
+mp_obj_t rt_getiter(mp_obj_t o_in) {
+    if (MP_OBJ_IS_SMALL_INT(o_in)) {
+        nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "'int' object is not iterable"));
     } else {
-        nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "'%s' object is not iterable", py_obj_get_type_str(o_in), NULL));
-    }
-}
-
-py_obj_t rt_iternext(py_obj_t o_in) {
-    if (IS_O(o_in, O_GEN_INSTANCE)) {
-        py_obj_base_t *self = o_in;
-        //py_obj_base_t *fun = self->u_gen_instance.state[0];
-        //assert(fun->kind == O_FUN_BC);
-        bool yield = py_execute_byte_code_2(&self->u_gen_instance.ip, &self->u_gen_instance.state[1], &self->u_gen_instance.sp);
-        if (yield) {
-            return *self->u_gen_instance.sp;
+        mp_obj_base_t *o = o_in;
+        if (o->type->getiter != NULL) {
+            return o->type->getiter(o_in);
         } else {
-            if (*self->u_gen_instance.sp == py_const_none) {
-                return py_const_stop_iteration;
-            } else {
-                // TODO return StopIteration with value *self->u_gen_instance.sp
-                return py_const_stop_iteration;
-            }
-        }
-
-    } else if (IS_O(o_in, O_RANGE_IT)) {
-        py_obj_base_t *o = o_in;
-        if ((o->u_range_it.step > 0 && o->u_range_it.cur < o->u_range_it.stop) || (o->u_range_it.step < 0 && o->u_range_it.cur > o->u_range_it.stop)) {
-            py_obj_t o_out = TO_SMALL_INT(o->u_range_it.cur);
-            o->u_range_it.cur += o->u_range_it.step;
-            return o_out;
-        } else {
-            return py_const_stop_iteration;
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "'%s' object is not iterable", o->type->name));
         }
+    }
+}
 
-    } else if (IS_O(o_in, O_TUPLE_IT) || IS_O(o_in, O_LIST_IT)) {
-        py_obj_base_t *o = o_in;
-        if (o->u_tuple_list_it.cur < o->u_tuple_list_it.obj->u_tuple_list.len) {
-            py_obj_t o_out = o->u_tuple_list_it.obj->u_tuple_list.items[o->u_tuple_list_it.cur];
-            o->u_tuple_list_it.cur += 1;
-            return o_out;
+mp_obj_t rt_iternext(mp_obj_t o_in) {
+    if (MP_OBJ_IS_SMALL_INT(o_in)) {
+        nlr_jump(mp_obj_new_exception_msg(rt_q_TypeError, "? 'int' object is not iterable"));
+    } else {
+        mp_obj_base_t *o = o_in;
+        if (o->type->iternext != NULL) {
+            return o->type->iternext(o_in);
         } else {
-            return py_const_stop_iteration;
+            nlr_jump(mp_obj_new_exception_msg_1_arg(rt_q_TypeError, "? '%s' object is not iterable", o->type->name));
         }
-
-    } else {
-        nlr_jump(py_obj_new_exception_2(rt_q_TypeError, "? '%s' object is not iterable", py_obj_get_type_str(o_in), NULL));
     }
 }
 
-py_obj_t rt_import_name(qstr name, py_obj_t fromlist, py_obj_t level) {
+mp_obj_t rt_import_name(qstr name, mp_obj_t fromlist, mp_obj_t level) {
     // build args array
-    py_obj_t args[5];
-    args[0] = py_obj_new_str(name);
-    args[1] = py_const_none; // TODO should be globals
-    args[2] = py_const_none; // TODO should be locals
+    mp_obj_t args[5];
+    args[0] = mp_obj_new_str(name);
+    args[1] = mp_const_none; // TODO should be globals
+    args[2] = mp_const_none; // TODO should be locals
     args[3] = fromlist;
     args[4] = level; // must be 0; we don't yet support other values
 
     // TODO lookup __import__ and call that instead of going straight to builtin implementation
-    return py_builtin___import__(5, args);
+    return mp_builtin___import__(5, args);
 }
 
-py_obj_t rt_import_from(py_obj_t module, qstr name) {
-    py_obj_t x = rt_load_attr(module, name);
+mp_obj_t rt_import_from(mp_obj_t module, qstr name) {
+    mp_obj_t x = rt_load_attr(module, name);
     /* TODO convert AttributeError to ImportError
     if (fail) {
         (ImportError, "cannot import name %s", qstr_str(name), NULL)