diff --git a/include/pocketpy/common/vector.h b/include/pocketpy/common/vector.h
index 97ba719b..c40a8b44 100644
--- a/include/pocketpy/common/vector.h
+++ b/include/pocketpy/common/vector.h
@@ -9,17 +9,17 @@
 
 typedef struct c11_array {
     void* data;
-    int count;
+    int length;
     int elem_size;
 } c11_array;
 
-void c11_array__ctor(c11_array* self, int elem_size, int count);
+void c11_array__ctor(c11_array* self, int elem_size, int length);
 void c11_array__dtor(c11_array* self);
 c11_array c11_array__copy(const c11_array* self);
 
 typedef struct c11_vector {
     void* data;
-    int count;
+    int length;
     int capacity;
     int elem_size;
 } c11_vector;
@@ -39,43 +39,43 @@ c11_array c11_vector__submit(c11_vector* self);
 
 #define c11_vector__push(T, self, elem)                                                            \
     do {                                                                                           \
-        if((self)->count == (self)->capacity) c11_vector__reserve((self), (self)->capacity * 2);   \
-        ((T*)(self)->data)[(self)->count] = (elem);                                                \
-        (self)->count++;                                                                           \
+        if((self)->length == (self)->capacity) c11_vector__reserve((self), (self)->capacity * 2);  \
+        ((T*)(self)->data)[(self)->length] = (elem);                                               \
+        (self)->length++;                                                                          \
     } while(0)
 
-#define c11_vector__pop(self) (--(self)->count)
+#define c11_vector__pop(self) (--(self)->length)
 
-#define c11_vector__back(T, self) (((T*)(self)->data)[(self)->count - 1])
+#define c11_vector__back(T, self) (((T*)(self)->data)[(self)->length - 1])
 
 #define c11_vector__extend(T, self, p, size)                                                       \
     do {                                                                                           \
-        c11_vector__reserve((self), (self)->count + (size));                                       \
-        memcpy((T*)(self)->data + (self)->count, (p), (size) * sizeof(T));                         \
-        (self)->count += (size);                                                                   \
+        c11_vector__reserve((self), (self)->length + (size));                                      \
+        memcpy((T*)(self)->data + (self)->length, (p), (size) * sizeof(T));                        \
+        (self)->length += (size);                                                                  \
     } while(0)
 
 #define c11_vector__insert(T, self, index, elem)                                                   \
     do {                                                                                           \
-        if((self)->count == (self)->capacity) c11_vector__reserve((self), (self)->capacity * 2);   \
+        if((self)->length == (self)->capacity) c11_vector__reserve((self), (self)->capacity * 2);  \
         T* p = (T*)(self)->data + (index);                                                         \
-        memmove(p + 1, p, ((self)->count - (index)) * sizeof(T));                                  \
+        memmove(p + 1, p, ((self)->length - (index)) * sizeof(T));                                 \
         *p = (elem);                                                                               \
-        (self)->count++;                                                                           \
+        (self)->length++;                                                                          \
     } while(0)
 
 #define c11_vector__erase(T, self, index)                                                          \
     do {                                                                                           \
         T* p = (T*)(self)->data + (index);                                                         \
-        memmove(p, p + 1, ((self)->count - (index)-1) * sizeof(T));                                \
-        (self)->count--;                                                                           \
+        memmove(p, p + 1, ((self)->length - (index)-1) * sizeof(T));                               \
+        (self)->length--;                                                                          \
     } while(0)
 
 #define c11__reverse(T, self)                                                                      \
     do {                                                                                           \
         if(!self->data) break;                                                                     \
         T* p = (T*)(self)->data;                                                                   \
-        T* q = (T*)(self)->data + (self)->count - 1;                                               \
+        T* q = (T*)(self)->data + (self)->length - 1;                                              \
         while(p < q) {                                                                             \
             T tmp = *p;                                                                            \
             *p = *q;                                                                               \
@@ -87,4 +87,4 @@ c11_array c11_vector__submit(c11_vector* self);
 
 // NOTE: here we do an extra NULL check for it to avoid UB
 #define c11__foreach(T, self, it)                                                                  \
-    for(T* it = (self)->data; it && it != (T*)(self)->data + (self)->count; it++)
+    for(T* it = (self)->data; it && it != (T*)(self)->data + (self)->length; it++)
diff --git a/include/pocketpy/xmacros/smallmap.h b/include/pocketpy/xmacros/smallmap.h
index ddf464d4..10bfee54 100644
--- a/include/pocketpy/xmacros/smallmap.h
+++ b/include/pocketpy/xmacros/smallmap.h
@@ -1,27 +1,27 @@
 #if !defined(SMALLMAP_T__HEADER) && !defined(SMALLMAP_T__SOURCE)
-    #include "pocketpy/common/vector.h"
+#include "pocketpy/common/vector.h"
 
-    #define SMALLMAP_T__HEADER
-    #define SMALLMAP_T__SOURCE
-    /* Input */
-    #define K int
-    #define V float
-    #define NAME c11_smallmap_i2f
+#define SMALLMAP_T__HEADER
+#define SMALLMAP_T__SOURCE
+/* Input */
+#define K int
+#define V float
+#define NAME c11_smallmap_i2f
 #endif
 
 /* Optional Input */
 #ifndef less
-    #define less(a, b) ((a) < (b))
+#define less(a, b) ((a) < (b))
 #endif
 
 #ifndef equal
-    #define equal(a, b) ((a) == (b))
+#define equal(a, b) ((a) == (b))
 #endif
 
 /* Temprary macros */
-#define partial_less(a, b)      less((a).key, (b))
-#define CONCAT(A, B)            CONCAT_(A, B)
-#define CONCAT_(A, B)           A##B
+#define partial_less(a, b) less((a).key, (b))
+#define CONCAT(A, B) CONCAT_(A, B)
+#define CONCAT_(A, B) A##B
 
 #define KV CONCAT(NAME, _KV)
 #define METHOD(name) CONCAT(NAME, CONCAT(__, name))
@@ -56,9 +56,7 @@ void METHOD(ctor)(NAME* self) {
     c11_vector__reserve(self, 4);
 }
 
-void METHOD(dtor)(NAME* self) {
-    c11_vector__dtor(self);
-}
+void METHOD(dtor)(NAME* self) { c11_vector__dtor(self); }
 
 NAME* METHOD(new)() {
     NAME* self = malloc(sizeof(NAME));
@@ -73,10 +71,10 @@ void METHOD(delete)(NAME* self) {
 
 void METHOD(set)(NAME* self, K key, V value) {
     int index;
-    c11__lower_bound(KV, self->data, self->count, key, partial_less, &index);
-    if(index != self->count){
+    c11__lower_bound(KV, self->data, self->length, key, partial_less, &index);
+    if(index != self->length) {
         KV* it = c11__at(KV, self, index);
-        if(equal(it->key, key)){
+        if(equal(it->key, key)) {
             it->value = value;
             return;
         }
@@ -87,8 +85,8 @@ void METHOD(set)(NAME* self, K key, V value) {
 
 V* METHOD(try_get)(const NAME* self, K key) {
     int index;
-    c11__lower_bound(KV, self->data, self->count, key, partial_less, &index);
-    if(index != self->count){
+    c11__lower_bound(KV, self->data, self->length, key, partial_less, &index);
+    if(index != self->length) {
         KV* it = c11__at(KV, self, index);
         if(equal(it->key, key)) return &it->value;
     }
@@ -100,16 +98,14 @@ V METHOD(get)(const NAME* self, K key, V default_value) {
     return p ? *p : default_value;
 }
 
-bool METHOD(contains)(const NAME* self, K key) {
-    return METHOD(try_get)(self, key) != NULL;
-}
+bool METHOD(contains)(const NAME* self, K key) { return METHOD(try_get)(self, key) != NULL; }
 
 bool METHOD(del)(NAME* self, K key) {
     int index;
-    c11__lower_bound(KV, self->data, self->count, key, partial_less, &index);
-    if(index != self->count){
+    c11__lower_bound(KV, self->data, self->length, key, partial_less, &index);
+    if(index != self->length) {
         KV* it = c11__at(KV, self, index);
-        if(equal(it->key, key)){
+        if(equal(it->key, key)) {
             c11_vector__erase(KV, self, index);
             return true;
         }
@@ -117,9 +113,7 @@ bool METHOD(del)(NAME* self, K key) {
     return false;
 }
 
-void METHOD(clear)(NAME* self) {
-    c11_vector__clear(self);
-}
+void METHOD(clear)(NAME* self) { c11_vector__clear(self); }
 
 #endif
 
diff --git a/src/common/memorypool.c b/src/common/memorypool.c
index 4b01314a..34c19a7c 100644
--- a/src/common/memorypool.c
+++ b/src/common/memorypool.c
@@ -13,13 +13,13 @@ typedef struct LinkedListNode {
 } LinkedListNode;
 
 typedef struct LinkedList {
-    int count;
+    int length;
     LinkedListNode head;
     LinkedListNode tail;
 } LinkedList;
 
 static void LinkedList__ctor(LinkedList* self) {
-    self->count = 0;
+    self->length = 0;
     self->head.prev = NULL;
     self->head.next = &self->tail;
     self->tail.prev = &self->head;
@@ -31,7 +31,7 @@ static void LinkedList__push_back(LinkedList* self, LinkedListNode* node) {
     node->next = &self->tail;
     self->tail.prev->next = node;
     self->tail.prev = node;
-    self->count++;
+    self->length++;
 }
 
 static void LinkedList__push_front(LinkedList* self, LinkedListNode* node) {
@@ -39,25 +39,25 @@ static void LinkedList__push_front(LinkedList* self, LinkedListNode* node) {
     node->next = self->head.next;
     self->head.next->prev = node;
     self->head.next = node;
-    self->count++;
+    self->length++;
 }
 
 static void LinkedList__pop_back(LinkedList* self) {
-    assert(self->count > 0);
+    assert(self->length > 0);
     self->tail.prev->prev->next = &self->tail;
     self->tail.prev = self->tail.prev->prev;
-    self->count--;
+    self->length--;
 }
 
 static LinkedListNode* LinkedList__back(LinkedList* self) {
-    assert(self->count > 0);
+    assert(self->length > 0);
     return self->tail.prev;
 }
 
 static void LinkedList__erase(LinkedList* self, LinkedListNode* node) {
     node->prev->next = node->next;
     node->next->prev = node->prev;
-    self->count--;
+    self->length--;
 }
 
 #define LinkedList__apply(self, __STATEMENTS__) \
@@ -135,7 +135,7 @@ static void MemoryPool__ctor(MemoryPool* self) {
 
 static void* MemoryPool__alloc(MemoryPool* self) {
     MemoryPoolArena* arena;
-    if(self->_arenas.count == 0){
+    if(self->_arenas.length == 0){
         arena = malloc(sizeof(MemoryPoolArena));
         MemoryPoolArena__ctor(arena);
         LinkedList__push_back(&self->_arenas, (LinkedListNode*)arena);
@@ -164,7 +164,7 @@ static void MemoryPool__dealloc(MemoryPool* self, void* p) {
 
 static void MemoryPool__shrink_to_fit(MemoryPool* self) {
     const int MIN_ARENA_COUNT = PK_GC_MIN_THRESHOLD * 100 / (kPoolObjectArenaSize);
-    if(self->_arenas.count < MIN_ARENA_COUNT) return;
+    if(self->_arenas.length < MIN_ARENA_COUNT) return;
     LinkedList__apply(&self->_arenas,
             MemoryPoolArena* arena = (MemoryPoolArena*)node;
             if(MemoryPoolArena__full(arena)) {
@@ -301,8 +301,8 @@ void Pools_debug_info(char* buffer, int size) {
     );
     buffer += n; size -= n;
     // PoolObject
-    int empty_arenas = PoolObject._empty_arenas.count;
-    int arenas = PoolObject._arenas.count;
+    int empty_arenas = PoolObject._empty_arenas.length;
+    int arenas = PoolObject._arenas.length;
     // print empty arenas count
     n = snprintf(
         buffer, size, "PoolObject: %d empty arenas, %d arenas\n",
diff --git a/src/common/sstream.c b/src/common/sstream.c
index 425e6901..0e19bf24 100644
--- a/src/common/sstream.c
+++ b/src/common/sstream.c
@@ -13,7 +13,7 @@
 void c11_sbuf__ctor(c11_sbuf* self) {
     c11_vector__ctor(&self->data, sizeof(char));
     c11_vector__reserve(&self->data, sizeof(c11_string) + 100);
-    self->data.count = sizeof(c11_string);
+    self->data.length = sizeof(c11_string);
 }
 
 void c11_sbuf__dtor(c11_sbuf* self) { c11_vector__dtor(&self->data); }
@@ -28,18 +28,18 @@ void c11_sbuf__write_pad(c11_sbuf* self, int count, char pad) {
 
 void c11_sbuf__write_int(c11_sbuf* self, int i) {
     // len('-2147483648') == 11
-    c11_vector__reserve(&self->data, self->data.count + 11 + 1);
-    char* p = (char*)self->data.data + self->data.count;
+    c11_vector__reserve(&self->data, self->data.length + 11 + 1);
+    char* p = (char*)self->data.data + self->data.length;
     int n = snprintf(p, 11 + 1, "%d", i);
-    self->data.count += n;
+    self->data.length += n;
 }
 
 void c11_sbuf__write_i64(c11_sbuf* self, int64_t val) {
     // len('-9223372036854775808') == 20
-    c11_vector__reserve(&self->data, self->data.count + 20 + 1);
-    char* p = (char*)self->data.data + self->data.count;
+    c11_vector__reserve(&self->data, self->data.length + 20 + 1);
+    char* p = (char*)self->data.data + self->data.length;
     int n = snprintf(p, 20 + 1, "%lld", (long long)val);
-    self->data.count += n;
+    self->data.length += n;
 }
 
 void c11_sbuf__write_f64(c11_sbuf* self, double val, int precision) {
@@ -143,7 +143,7 @@ c11_string* c11_sbuf__submit(c11_sbuf* self) {
     c11_vector__push(char, &self->data, '\0');
     c11_array arr = c11_vector__submit(&self->data);
     c11_string* retval = arr.data;
-    retval->size = arr.count - sizeof(c11_string) - 1;
+    retval->size = arr.length - sizeof(c11_string) - 1;
     return retval;
 }
 
diff --git a/src/common/strname.c b/src/common/strname.c
index b0b270ad..40ca110c 100644
--- a/src/common/strname.c
+++ b/src/common/strname.c
@@ -12,19 +12,20 @@ static c11_vector /*T=char* */ _r_interned;
 
 void py_Name__initialize() {
     c11_smallmap_s2n__ctor(&_interned);
-    for(int i = 0; i < _r_interned.count; i++) {
+    for(int i = 0; i < _r_interned.length; i++) {
         free(c11__at(char*, &_r_interned, i));
     }
     c11_vector__ctor(&_r_interned, sizeof(c11_sv));
 
-#define MAGIC_METHOD(x) if(x != py_name(#x)) abort();
+#define MAGIC_METHOD(x)                                                                            \
+    if(x != py_name(#x)) abort();
 #include "pocketpy/xmacros/magics.h"
 #undef MAGIC_METHOD
 }
 
 void py_Name__finalize() {
     // free all char*
-    for(int i = 0; i < _r_interned.count; i++) {
+    for(int i = 0; i < _r_interned.length; i++) {
         free(c11__getitem(char*, &_r_interned, i));
     }
     c11_smallmap_s2n__dtor(&_interned);
@@ -38,27 +39,26 @@ py_Name py_namev(c11_sv name) {
     uint16_t index = c11_smallmap_s2n__get(&_interned, name, 0);
     if(index != 0) return index;
     // generate new index
-    if(_interned.count > 65530) c11__abort("py_Name index overflow");
+    if(_interned.length > 65530) c11__abort("py_Name index overflow");
     // NOTE: we must allocate the string in the heap so iterators are not invalidated
     char* p = malloc(name.size + 1);
     memcpy(p, name.data, name.size);
     p[name.size] = '\0';
     c11_vector__push(char*, &_r_interned, p);
-    index = _r_interned.count;  // 1-based
+    index = _r_interned.length;  // 1-based
     // save to _interned
     c11_smallmap_s2n__set(&_interned, (c11_sv){p, name.size}, index);
-    assert(_interned.count == _r_interned.count);
+    assert(_interned.length == _r_interned.length);
     return index;
 }
 
 const char* py_name2str(py_Name index) {
-    assert(index > 0 && index <= _interned.count);
+    assert(index > 0 && index <= _interned.length);
     return c11__getitem(char*, &_r_interned, index - 1);
 }
 
 c11_sv py_name2sv(py_Name index) {
-    assert(index > 0 && index <= _interned.count);
+    assert(index > 0 && index <= _interned.length);
     const char* p = py_name2str(index);
     return (c11_sv){p, strlen(p)};
 }
-
diff --git a/src/common/vector.c b/src/common/vector.c
index 97649f96..ca890792 100644
--- a/src/common/vector.c
+++ b/src/common/vector.c
@@ -3,28 +3,28 @@
 #include <stdlib.h>
 #include <string.h>
 
-void c11_array__ctor(c11_array* self, int elem_size, int count){
-    self->data = malloc(elem_size * count);
-    self->count = count;
+void c11_array__ctor(c11_array* self, int elem_size, int length){
+    self->data = malloc(elem_size * length);
+    self->length = length;
     self->elem_size = elem_size;
 }
 
 void c11_array__dtor(c11_array* self){
     free(self->data);
     self->data = NULL;
-    self->count = 0;
+    self->length = 0;
 }
 
 c11_array c11_array__copy(const c11_array* self){
     c11_array retval;
-    c11_array__ctor(&retval, self->elem_size, self->count);
-    memcpy(retval.data, self->data, self->elem_size * self->count);
+    c11_array__ctor(&retval, self->elem_size, self->length);
+    memcpy(retval.data, self->data, self->elem_size * self->length);
     return retval;
 }
 
 void c11_vector__ctor(c11_vector* self, int elem_size){
     self->data = NULL;
-    self->count = 0;
+    self->length = 0;
     self->capacity = 0;
     self->elem_size = elem_size;
 }
@@ -32,7 +32,7 @@ void c11_vector__ctor(c11_vector* self, int elem_size){
 void c11_vector__dtor(c11_vector* self){
     if(self->data) free(self->data);
     self->data = NULL;
-    self->count = 0;
+    self->length = 0;
     self->capacity = 0;
 }
 
@@ -40,8 +40,8 @@ c11_vector c11_vector__copy(const c11_vector* self){
     c11_vector retval;
     c11_vector__ctor(&retval, self->elem_size);
     c11_vector__reserve(&retval, self->capacity);
-    memcpy(retval.data, self->data, self->elem_size * self->count);
-    retval.count = self->count;
+    memcpy(retval.data, self->data, self->elem_size * self->length);
+    retval.length = self->length;
     return retval;
 }
 
@@ -53,18 +53,18 @@ void c11_vector__reserve(c11_vector* self, int capacity){
 }
 
 void c11_vector__clear(c11_vector* self){
-    self->count = 0;
+    self->length = 0;
 }
 
 void* c11_vector__emplace(c11_vector* self){
-    if(self->count == self->capacity) c11_vector__reserve(self, self->capacity*2);
-    void* p = (char*)self->data + self->elem_size * self->count;
-    self->count++;
+    if(self->length == self->capacity) c11_vector__reserve(self, self->capacity*2);
+    void* p = (char*)self->data + self->elem_size * self->length;
+    self->length++;
     return p;
 }
 
 bool c11_vector__contains(const c11_vector *self, void *elem){
-    for(int i = 0; i < self->count; i++){
+    for(int i = 0; i < self->length; i++){
         void* p = (char*)self->data + self->elem_size * i;
         if(memcmp(p, elem, self->elem_size) == 0) return true;
     }
@@ -74,11 +74,11 @@ bool c11_vector__contains(const c11_vector *self, void *elem){
 c11_array c11_vector__submit(c11_vector* self){
     c11_array retval = {
         .data = self->data,
-        .count = self->count,
+        .length = self->length,
         .elem_size = self->elem_size
     };
     self->data = NULL;
-    self->count = 0;
+    self->length = 0;
     self->capacity = 0;
     return retval;
 }
diff --git a/src/compiler/compiler.c b/src/compiler/compiler.c
index 42f512e5..5989c852 100644
--- a/src/compiler/compiler.c
+++ b/src/compiler/compiler.c
@@ -454,11 +454,11 @@ typedef struct SequenceExpr {
 
 static void SequenceExpr__emit_(Expr* self_, Ctx* ctx) {
     SequenceExpr* self = (SequenceExpr*)self_;
-    for(int i = 0; i < self->items.count; i++) {
+    for(int i = 0; i < self->items.length; i++) {
         Expr* item = c11__getitem(Expr*, &self->items, i);
         vtemit_(item, ctx);
     }
-    Ctx__emit_(ctx, self->opcode, self->items.count, self->line);
+    Ctx__emit_(ctx, self->opcode, self->items.length, self->line);
 }
 
 void SequenceExpr__dtor(Expr* self_) {
@@ -472,7 +472,7 @@ bool TupleExpr__emit_store(Expr* self_, Ctx* ctx) {
     // TOS is an iterable
     // items may contain StarredExpr, we should check it
     int starred_i = -1;
-    for(int i = 0; i < self->items.count; i++) {
+    for(int i = 0; i < self->items.length; i++) {
         Expr* e = c11__getitem(Expr*, &self->items, i);
         if(e->vt->is_starred) {
             if(((StarredExpr*)e)->level > 0) {
@@ -485,24 +485,24 @@ bool TupleExpr__emit_store(Expr* self_, Ctx* ctx) {
     }
 
     if(starred_i == -1) {
-        Bytecode* prev = c11__at(Bytecode, &ctx->co->codes, ctx->co->codes.count - 1);
-        if(prev->op == OP_BUILD_TUPLE && prev->arg == self->items.count) {
+        Bytecode* prev = c11__at(Bytecode, &ctx->co->codes, ctx->co->codes.length - 1);
+        if(prev->op == OP_BUILD_TUPLE && prev->arg == self->items.length) {
             // build tuple and unpack it is meaningless
             Ctx__revert_last_emit_(ctx);
         } else {
-            Ctx__emit_(ctx, OP_UNPACK_SEQUENCE, self->items.count, self->line);
+            Ctx__emit_(ctx, OP_UNPACK_SEQUENCE, self->items.length, self->line);
         }
     } else {
         // starred assignment target must be in a tuple
-        if(self->items.count == 1) return false;
+        if(self->items.length == 1) return false;
         // starred assignment target must be the last one (differ from cpython)
-        if(starred_i != self->items.count - 1) return false;
+        if(starred_i != self->items.length - 1) return false;
         // a,*b = [1,2,3]
         // stack is [1,2,3] -> [1,[2,3]]
-        Ctx__emit_(ctx, OP_UNPACK_EX, self->items.count - 1, self->line);
+        Ctx__emit_(ctx, OP_UNPACK_EX, self->items.length - 1, self->line);
     }
     // do reverse emit
-    for(int i = self->items.count - 1; i >= 0; i--) {
+    for(int i = self->items.length - 1; i >= 0; i--) {
         Expr* e = c11__getitem(Expr*, &self->items, i);
         bool ok = vtemit_store(e, ctx);
         if(!ok) return false;
@@ -822,7 +822,7 @@ static void BinaryExpr__emit_(Expr* self_, Ctx* ctx) {
 
     Ctx__emit_(ctx, opcode, arg, self->line);
 
-    for(int i = 0; i < jmps.count; i++) {
+    for(int i = 0; i < jmps.length; i++) {
         Ctx__patch_jump(ctx, c11__getitem(int, &jmps, i));
     }
     c11_vector__dtor(&jmps);
@@ -1069,8 +1069,8 @@ void CallExpr__emit_(Expr* self_, Ctx* ctx) {
         Ctx__emit_int(ctx, e->key, self->line);
         vtemit_(e->val, ctx);
     }
-    int KWARGC = self->kwargs.count;
-    int ARGC = self->args.count;
+    int KWARGC = self->kwargs.length;
+    int ARGC = self->args.length;
     assert(KWARGC < 256 && ARGC < 256);
     Ctx__emit_(ctx, opcode, (KWARGC << 8) | ARGC, self->line);
 }
@@ -1101,7 +1101,7 @@ static void Ctx__ctor(Ctx* self, CodeObject* co, FuncDecl* func, int level) {
 
 static void Ctx__dtor(Ctx* self) {
     // clean the expr stack
-    for(int i = 0; i < self->s_expr.count; i++) {
+    for(int i = 0; i < self->s_expr.length; i++) {
         vtdelete(c11__getitem(Expr*, &self->s_expr, i));
     }
     c11_vector__dtor(&self->s_expr);
@@ -1123,16 +1123,16 @@ static int Ctx__get_loop(Ctx* self) {
 }
 
 static CodeBlock* Ctx__enter_block(Ctx* self, CodeBlockType type) {
-    CodeBlock block = {type, self->curr_iblock, self->co->codes.count, -1, -1};
+    CodeBlock block = {type, self->curr_iblock, self->co->codes.length, -1, -1};
     c11_vector__push(CodeBlock, &self->co->blocks, block);
-    self->curr_iblock = self->co->blocks.count - 1;
+    self->curr_iblock = self->co->blocks.length - 1;
     return c11__at(CodeBlock, &self->co->blocks, self->curr_iblock);
 }
 
 static void Ctx__exit_block(Ctx* self) {
     CodeBlock* block = c11__at(CodeBlock, &self->co->blocks, self->curr_iblock);
     CodeBlockType curr_type = block->type;
-    block->end = self->co->codes.count;
+    block->end = self->co->codes.length;
     self->curr_iblock = block->parent;
     assert(self->curr_iblock >= 0);
     if(curr_type == CodeBlockType_FOR_LOOP) {
@@ -1161,7 +1161,7 @@ static int Ctx__emit_virtual(Ctx* self, Opcode opcode, uint16_t arg, int line, b
     BytecodeEx bcx = {line, is_virtual, self->curr_iblock};
     c11_vector__push(Bytecode, &self->co->codes, bc);
     c11_vector__push(BytecodeEx, &self->co->codes_ex, bcx);
-    int i = self->co->codes.count - 1;
+    int i = self->co->codes.length - 1;
     BytecodeEx* codes_ex = (BytecodeEx*)self->co->codes_ex.data;
     if(line == BC_KEEPLINE) { codes_ex[i].lineno = i >= 1 ? codes_ex[i - 1].lineno : 1; }
     return i;
@@ -1188,14 +1188,14 @@ static int Ctx__emit_int(Ctx* self, int64_t value, int line) {
 
 static void Ctx__patch_jump(Ctx* self, int index) {
     Bytecode* co_codes = (Bytecode*)self->co->codes.data;
-    int target = self->co->codes.count;
+    int target = self->co->codes.length;
     Bytecode__set_signed_arg(&co_codes[index], target - index);
 }
 
 static bool Ctx__add_label(Ctx* self, py_Name name) {
     bool ok = c11_smallmap_n2i__contains(&self->co->labels, name);
     if(ok) return false;
-    c11_smallmap_n2i__set(&self->co->labels, name, self->co->codes.count);
+    c11_smallmap_n2i__set(&self->co->labels, name, self->co->codes.length);
     return true;
 }
 
@@ -1212,7 +1212,7 @@ static int Ctx__add_const_string(Ctx* self, c11_sv key) {
         py_TValue tmp;
         py_newstrn(&tmp, key.data, key.size);
         c11_vector__push(py_TValue, &self->co->consts, tmp);
-        int index = self->co->consts.count - 1;
+        int index = self->co->consts.length - 1;
         c11_smallmap_s2n__set(&self->co_consts_string_dedup_map,
                               c11_string__sv(PyObject__userdata(tmp._obj)),
                               index);
@@ -1223,7 +1223,7 @@ static int Ctx__add_const_string(Ctx* self, c11_sv key) {
 static int Ctx__add_const(Ctx* self, py_Ref v) {
     assert(v->type != tp_str);
     c11_vector__push(py_TValue, &self->co->consts, *v);
-    return self->co->consts.count - 1;
+    return self->co->consts.length - 1;
 }
 
 static void Ctx__emit_store_name(Ctx* self, NameScope scope, py_Name name, int line) {
@@ -1237,7 +1237,7 @@ static void Ctx__emit_store_name(Ctx* self, NameScope scope, py_Name name, int l
 
 // emit top -> pop -> delete
 static void Ctx__s_emit_top(Ctx* self) {
-    assert(self->s_expr.count);
+    assert(self->s_expr.length);
     Expr* top = c11_vector__back(Expr*, &self->s_expr);
     vtemit_(top, self);
     vtdelete(top);
@@ -1249,16 +1249,16 @@ static void Ctx__s_push(Ctx* self, Expr* expr) { c11_vector__push(Expr*, &self->
 
 // top
 static Expr* Ctx__s_top(Ctx* self) {
-    assert(self->s_expr.count);
+    assert(self->s_expr.length);
     return c11_vector__back(Expr*, &self->s_expr);
 }
 
 // size
-static int Ctx__s_size(Ctx* self) { return self->s_expr.count; }
+static int Ctx__s_size(Ctx* self) { return self->s_expr.length; }
 
 // pop -> delete
 static void Ctx__s_pop(Ctx* self) {
-    assert(self->s_expr.count);
+    assert(self->s_expr.length);
     Expr* top = c11_vector__back(Expr*, &self->s_expr);
     vtdelete(top);
     c11_vector__pop(&self->s_expr);
@@ -1266,7 +1266,7 @@ static void Ctx__s_pop(Ctx* self) {
 
 // pop move
 static Expr* Ctx__s_popx(Ctx* self) {
-    assert(self->s_expr.count);
+    assert(self->s_expr.length);
     Expr* top = c11_vector__back(Expr*, &self->s_expr);
     c11_vector__pop(&self->s_expr);
     return top;
@@ -1329,7 +1329,7 @@ static void Compiler__dtor(Compiler* self) {
     if((err = B)) return err
 
 static NameScope name_scope(Compiler* self) {
-    NameScope s = self->contexts.count > 1 ? NAME_LOCAL : NAME_GLOBAL;
+    NameScope s = self->contexts.length > 1 ? NAME_LOCAL : NAME_GLOBAL;
     if(self->src->is_dynamic && s == NAME_GLOBAL) s = NAME_GLOBAL_UNKNOWN;
     return s;
 }
@@ -1338,7 +1338,7 @@ Error* SyntaxError(Compiler* self, const char* fmt, ...) {
     Error* err = malloc(sizeof(Error));
     err->src = self->src;
     PK_INCREF(self->src);
-    Token* t = self->i == self->tokens.count ? prev() : curr();
+    Token* t = self->i == self->tokens.length ? prev() : curr();
     err->lineno = t->line;
     va_list args;
     va_start(args, fmt);
@@ -1451,7 +1451,7 @@ static Error* EXPR_VARS(Compiler* self) {
 static void push_global_context(Compiler* self, CodeObject* co) {
     co->start_line = self->i == 0 ? 1 : prev()->line;
     Ctx* ctx = c11_vector__emplace(&self->contexts);
-    Ctx__ctor(ctx, co, NULL, self->contexts.count);
+    Ctx__ctor(ctx, co, NULL, self->contexts.length);
 }
 
 static Error* pop_context(Compiler* self) {
@@ -1473,11 +1473,11 @@ static Error* pop_context(Compiler* self) {
     if(co->nlocals > PK_MAX_CO_VARNAMES) {
         return SyntaxError(self, "maximum number of local variables exceeded");
     }
-    if(co->consts.count > 65530) {
+    if(co->consts.length > 65530) {
         return SyntaxError(self, "maximum number of constants exceeded");
     }
     // pre-compute LOOP_BREAK and LOOP_CONTINUE
-    for(int i = 0; i < codes->count; i++) {
+    for(int i = 0; i < codes->length; i++) {
         Bytecode* bc = c11__at(Bytecode, codes, i);
         if(bc->op == OP_LOOP_CONTINUE) {
             CodeBlock* block = c11__at(CodeBlock, &ctx()->co->blocks, bc->arg);
@@ -1492,7 +1492,7 @@ static Error* pop_context(Compiler* self) {
     if(func) {
         // check generator
         Bytecode* codes = func->code.codes.data;
-        int codes_length = func->code.codes.count;
+        int codes_length = func->code.codes.length;
 
         for(int i = 0; i < codes_length; i++) {
             if(codes[i].op == OP_YIELD_VALUE) {
@@ -1510,7 +1510,7 @@ static Error* pop_context(Compiler* self) {
         }
         if(func->type == FuncType_UNSET) {
             bool is_simple = true;
-            if(func->kwargs.count > 0) is_simple = false;
+            if(func->kwargs.length > 0) is_simple = false;
             if(func->starred_arg >= 0) is_simple = false;
             if(func->starred_kwarg >= 0) is_simple = false;
 
@@ -1855,7 +1855,7 @@ static Error* exprCall(Compiler* self) {
                 c11_vector__push(CallExprKwArg, &e->kwargs, kw);
             } else {
                 // positional argument
-                if(e->kwargs.count > 0) {
+                if(e->kwargs.length > 0) {
                     return SyntaxError(self, "positional argument follows keyword argument");
                 }
                 c11_vector__push(Expr*, &e->args, Ctx__s_popx(ctx()));
@@ -1994,7 +1994,7 @@ static Error* compile_while_loop(Compiler* self) {
     // optional else clause
     if(match(TK_ELSE)) {
         check(compile_block_body(self, compile_stmt));
-        block->end2 = ctx()->co->codes.count;
+        block->end2 = ctx()->co->codes.length;
     }
     return NULL;
 }
@@ -2021,7 +2021,7 @@ static Error* compile_for_loop(Compiler* self) {
     // optional else clause
     if(match(TK_ELSE)) {
         check(compile_block_body(self, compile_stmt));
-        block->end2 = ctx()->co->codes.count;
+        block->end2 = ctx()->co->codes.length;
     }
     return NULL;
 }
@@ -2097,10 +2097,10 @@ static FuncDecl_ push_f_context(Compiler* self, c11_sv name, int* out_index) {
     // add_func_decl
     Ctx* top_ctx = ctx();
     c11_vector__push(FuncDecl_, &top_ctx->co->func_decls, decl);
-    *out_index = top_ctx->co->func_decls.count - 1;
+    *out_index = top_ctx->co->func_decls.length - 1;
     // push new context
     top_ctx = c11_vector__emplace(&self->contexts);
-    Ctx__ctor(top_ctx, &decl->code, decl, self->contexts.count);
+    Ctx__ctor(top_ctx, &decl->code, decl, self->contexts.length);
     return decl;
 }
 
@@ -2214,7 +2214,7 @@ static Error* compile_function(Compiler* self, int decorators) {
     check(compile_block_body(self, compile_stmt));
     check(pop_context(self));
 
-    if(decl->code.codes.count >= 2) {
+    if(decl->code.codes.length >= 2) {
         Bytecode* codes = (Bytecode*)decl->code.codes.data;
 
         if(codes[0].op == OP_LOAD_CONST && codes[1].op == OP_POP_TOP) {
@@ -2463,14 +2463,15 @@ static Error* compile_stmt(Compiler* self) {
             consume_end_stmt();
             break;
         case TK_YIELD:
-            if(self->contexts.count <= 1) return SyntaxError(self, "'yield' outside function");
+            if(self->contexts.length <= 1) return SyntaxError(self, "'yield' outside function");
             check(EXPR_TUPLE(self));
             Ctx__s_emit_top(ctx());
             Ctx__emit_(ctx(), OP_YIELD_VALUE, BC_NOARG, kw_line);
             consume_end_stmt();
             break;
         case TK_YIELD_FROM:
-            if(self->contexts.count <= 1) return SyntaxError(self, "'yield from' outside function");
+            if(self->contexts.length <= 1)
+                return SyntaxError(self, "'yield from' outside function");
             check(EXPR_TUPLE(self));
             Ctx__s_emit_top(ctx());
             Ctx__emit_(ctx(), OP_GET_ITER, BC_NOARG, kw_line);
@@ -2482,7 +2483,7 @@ static Error* compile_stmt(Compiler* self) {
             consume_end_stmt();
             break;
         case TK_RETURN:
-            if(self->contexts.count <= 1) return SyntaxError(self, "'return' outside function");
+            if(self->contexts.length <= 1) return SyntaxError(self, "'return' outside function");
             if(match_end_stmt(self)) {
                 Ctx__emit_(ctx(), OP_RETURN_VALUE, 1, kw_line);
             } else {
@@ -2672,7 +2673,7 @@ Error* pk_compile(SourceData_ src, CodeObject* out) {
 #if 0
     Token* data = (Token*)tokens.data;
     printf("%s\n", src->filename->data);
-    for(int i = 0; i < tokens.count; i++) {
+    for(int i = 0; i < tokens.length; i++) {
         Token* t = data + i;
         c11_string* tmp = c11_string__new2(t->start, t->length);
         if(t->value.index == TokenValue_STR) {
diff --git a/src/compiler/lexer.c b/src/compiler/lexer.c
index cccbad40..f9d5e50f 100644
--- a/src/compiler/lexer.c
+++ b/src/compiler/lexer.c
@@ -125,7 +125,7 @@ static void add_token_with_value(Lexer* self, TokenIndex type, TokenValue value)
                    self->brackets_level,
                    value};
     // handle "not in", "is not", "yield from"
-    if(self->nexts.count > 0) {
+    if(self->nexts.length > 0) {
         Token* back = &c11_vector__back(Token, &self->nexts);
         if(back->type == TK_NOT_KW && type == TK_IN) {
             back->type = TK_NOT_IN;
@@ -336,12 +336,12 @@ static Error* _eat_string(Lexer* self, c11_sbuf* buff, char quote, enum StringTy
 
                         // submit {expr} tokens
                         bool eof = false;
-                        int token_count = self->nexts.count;
+                        int token_count = self->nexts.length;
                         while(!eof) {
                             Error* err = lex_one_token(self, &eof, true);
                             if(err) return err;
                         }
-                        if(self->nexts.count == token_count) {
+                        if(self->nexts.length == token_count) {
                             // f'{}' is not allowed
                             return SyntaxError(self, "f-string: empty expression not allowed");
                         }
@@ -353,7 +353,7 @@ static Error* _eat_string(Lexer* self, c11_sbuf* buff, char quote, enum StringTy
                     } else {
                         return SyntaxError(self, "f-string: single '}' is not allowed");
                     }
-                }else{
+                } else {
                     c11_sbuf__write_char(buff, c);
                 }
             } else {
@@ -600,7 +600,7 @@ static Error* lex_one_token(Lexer* self, bool* eof, bool is_fstring) {
     if(is_fstring) return SyntaxError(self, "unterminated f-string expression");
 
     self->token_start = self->curr_char;
-    while(self->indents.count > 1) {
+    while(self->indents.length > 1) {
         c11_vector__pop(&self->indents);
         add_token(self, TK_DEDENT);
         return NULL;
@@ -637,7 +637,7 @@ Error* Lexer__process(SourceData_ src, TokenArray* out_tokens) {
 
 void TokenArray__dtor(TokenArray* self) {
     Token* data = self->data;
-    for(int i = 0; i < self->count; i++) {
+    for(int i = 0; i < self->length; i++) {
         if(data[i].value.index == TokenValue_STR) { c11_string__delete(data[i].value._str); }
     }
     c11_array__dtor(self);
diff --git a/src/interpreter/ceval.c b/src/interpreter/ceval.c
index 6c3f3c1c..715bc302 100644
--- a/src/interpreter/ceval.c
+++ b/src/interpreter/ceval.c
@@ -844,7 +844,7 @@ FrameResult VM__run_top_frame(VM* self) {
                         }
                     }
                 } else {
-                    for(int i = 0; i < dict->count; i++) {
+                    for(int i = 0; i < dict->length; i++) {
                         NameDict_KV* kv = c11__at(NameDict_KV, dict, i);
                         if(!kv->key) continue;
                         c11_sv name = py_name2sv(kv->key);
@@ -1124,21 +1124,21 @@ static bool stack_format_object(VM* self, c11_sv spec) {
     py_StackRef val = TOP();
     if(spec.size == 0) return py_str(val);
 
-    if(spec.data[0] == '!'){
-        if(c11_sv__startswith(spec, (c11_sv){"!r", 2})){
+    if(spec.data[0] == '!') {
+        if(c11_sv__startswith(spec, (c11_sv){"!r", 2})) {
             spec.data += 2;
             spec.size -= 2;
             if(!py_repr(val)) return false;
             py_assign(val, py_retval());
             if(spec.size == 0) return true;
-        }else{
+        } else {
             return ValueError("invalid conversion specifier (only !r is supported)");
         }
     }
 
     assert(spec.size > 0);
-    
-    if(spec.data[0] == ':'){
+
+    if(spec.data[0] == ':') {
         spec.data++;
         spec.size--;
     }
diff --git a/src/interpreter/frame.c b/src/interpreter/frame.c
index 6706e3c0..308ee517 100644
--- a/src/interpreter/frame.c
+++ b/src/interpreter/frame.c
@@ -81,7 +81,7 @@ int Frame__prepare_jump_exception_handler(Frame* self, ValueStack* _s) {
 
 void Frame__prepare_jump_break(Frame* self, ValueStack* _s, int target) {
     int iblock = Frame__iblock(self);
-    if(target >= self->co->codes.count) {
+    if(target >= self->co->codes.length) {
         while(iblock >= 0)
             iblock = Frame__exit_block(self, _s, iblock);
     } else {
diff --git a/src/interpreter/heap.c b/src/interpreter/heap.c
index a474ec4d..9840ac37 100644
--- a/src/interpreter/heap.c
+++ b/src/interpreter/heap.c
@@ -2,7 +2,7 @@
 #include "pocketpy/common/memorypool.h"
 #include "pocketpy/objects/base.h"
 
-void ManagedHeap__ctor(ManagedHeap *self, VM *vm){
+void ManagedHeap__ctor(ManagedHeap* self, VM* vm) {
     c11_vector__ctor(&self->no_gc, sizeof(PyObject*));
     c11_vector__ctor(&self->gen, sizeof(PyObject*));
 
@@ -13,12 +13,12 @@ void ManagedHeap__ctor(ManagedHeap *self, VM *vm){
     self->gc_on_delete = NULL;
 }
 
-void ManagedHeap__dtor(ManagedHeap *self){
-    for(int i = 0; i < self->gen.count; i++){
+void ManagedHeap__dtor(ManagedHeap* self) {
+    for(int i = 0; i < self->gen.length; i++) {
         PyObject* obj = c11__getitem(PyObject*, &self->gen, i);
         PyObject__delete(obj);
     }
-    for(int i = 0; i < self->no_gc.count; i++){
+    for(int i = 0; i < self->no_gc.length; i++) {
         PyObject* obj = c11__getitem(PyObject*, &self->no_gc, i);
         PyObject__delete(obj);
     }
@@ -26,47 +26,43 @@ void ManagedHeap__dtor(ManagedHeap *self){
     c11_vector__dtor(&self->gen);
 }
 
-void ManagedHeap__collect_if_needed(ManagedHeap *self){
+void ManagedHeap__collect_if_needed(ManagedHeap* self) {
     if(self->gc_counter < self->gc_threshold) return;
     self->gc_counter = 0;
     ManagedHeap__collect(self);
-    self->gc_threshold = self->gen.count * 2;
-    if(self->gc_threshold < PK_GC_MIN_THRESHOLD){
-        self->gc_threshold = PK_GC_MIN_THRESHOLD;
-    }
+    self->gc_threshold = self->gen.length * 2;
+    if(self->gc_threshold < PK_GC_MIN_THRESHOLD) { self->gc_threshold = PK_GC_MIN_THRESHOLD; }
 }
 
-int ManagedHeap__collect(ManagedHeap *self){
+int ManagedHeap__collect(ManagedHeap* self) {
     ManagedHeap__mark(self);
     int freed = ManagedHeap__sweep(self);
     return freed;
 }
 
-int ManagedHeap__sweep(ManagedHeap *self){
+int ManagedHeap__sweep(ManagedHeap* self) {
     c11_vector alive;
     c11_vector__ctor(&alive, sizeof(PyObject*));
-    c11_vector__reserve(&alive, self->gen.count / 2);
+    c11_vector__reserve(&alive, self->gen.length / 2);
 
-    for(int i = 0; i < self->gen.count; i++){
+    for(int i = 0; i < self->gen.length; i++) {
         PyObject* obj = c11__getitem(PyObject*, &self->gen, i);
         if(obj->gc_marked) {
             obj->gc_marked = false;
             c11_vector__push(PyObject*, &alive, obj);
         } else {
-            if(self->gc_on_delete){
-                self->gc_on_delete(self->vm, obj);
-            }
+            if(self->gc_on_delete) { self->gc_on_delete(self->vm, obj); }
             PyObject__delete(obj);
         }
     }
 
     // clear _no_gc marked flag
-    for(int i=0; i<self->no_gc.count; i++){
+    for(int i = 0; i < self->no_gc.length; i++) {
         PyObject* obj = c11__getitem(PyObject*, &self->no_gc, i);
         obj->gc_marked = false;
     }
 
-    int freed = self->gen.count - alive.count;
+    int freed = self->gen.length - alive.length;
 
     // destroy old gen
     c11_vector__dtor(&self->gen);
@@ -77,28 +73,28 @@ int ManagedHeap__sweep(ManagedHeap *self){
     return freed;
 }
 
-PyObject* ManagedHeap__new(ManagedHeap *self, py_Type type, int slots, int udsize){
+PyObject* ManagedHeap__new(ManagedHeap* self, py_Type type, int slots, int udsize) {
     PyObject* obj = PyObject__new(type, slots, udsize);
     c11_vector__push(PyObject*, &self->no_gc, obj);
     return obj;
 }
 
-PyObject* ManagedHeap__gcnew(ManagedHeap *self, py_Type type, int slots, int udsize){
+PyObject* ManagedHeap__gcnew(ManagedHeap* self, py_Type type, int slots, int udsize) {
     PyObject* obj = PyObject__new(type, slots, udsize);
     c11_vector__push(PyObject*, &self->gen, obj);
     self->gc_counter++;
     return obj;
 }
 
-PyObject* PyObject__new(py_Type type, int slots, int size){
+PyObject* PyObject__new(py_Type type, int slots, int size) {
     assert(slots >= 0 || slots == -1);
     PyObject* self;
     // header + slots + udsize
     size = sizeof(PyObject) + PK_OBJ_SLOTS_SIZE(slots) + size;
-    if(size <= kPoolObjectBlockSize){
+    if(size <= kPoolObjectBlockSize) {
         self = PoolObject_alloc();
         self->gc_is_large = false;
-    }else{
+    } else {
         self = malloc(size);
         self->gc_is_large = true;
     }
@@ -108,9 +104,9 @@ PyObject* PyObject__new(py_Type type, int slots, int size){
 
     // initialize slots or dict
     void* p = (char*)self + 8;
-    if(slots >= 0){
-        memset(p, 0, slots*sizeof(py_TValue));
-    }else{
+    if(slots >= 0) {
+        memset(p, 0, slots * sizeof(py_TValue));
+    } else {
         NameDict__ctor(p);
     }
     return self;
diff --git a/src/interpreter/vm.c b/src/interpreter/vm.c
index 28fa6d10..704edba8 100644
--- a/src/interpreter/vm.c
+++ b/src/interpreter/vm.c
@@ -317,7 +317,7 @@ py_Type pk_newtype(const char* name,
                    bool is_python,
                    bool is_sealed) {
     c11_vector* types = &pk_current_vm->types;
-    py_Type index = types->count;
+    py_Type index = types->length;
     py_TypeInfo* ti = c11_vector__emplace(types);
     py_TypeInfo* base_ti = base ? c11__at(py_TypeInfo, types, base) : NULL;
     if(base_ti && base_ti->is_sealed) {
@@ -340,7 +340,7 @@ py_Type py_newtype(const char* name, py_Type base, const py_GlobalRef module, vo
 static bool
     prepare_py_call(py_TValue* buffer, py_Ref argv, py_Ref p1, int kwargc, const FuncDecl* decl) {
     const CodeObject* co = &decl->code;
-    int decl_argc = decl->args.count;
+    int decl_argc = decl->args.length;
 
     if(p1 - argv < decl_argc) {
         return TypeError("%s() takes %d positional arguments but %d were given",
@@ -452,9 +452,9 @@ FrameResult VM__vectorcall(VM* self, uint16_t argc, uint16_t kwargc, bool opcall
                 }
             }
             case FuncType_SIMPLE:
-                if(p1 - argv != fn->decl->args.count) {
+                if(p1 - argv != fn->decl->args.length) {
                     const char* fmt = "%s() takes %d positional arguments but %d were given";
-                    TypeError(fmt, co->name->data, fn->decl->args.count, p1 - argv);
+                    TypeError(fmt, co->name->data, fn->decl->args.length, p1 - argv);
                     return RES_ERROR;
                 }
                 if(kwargc) {
@@ -552,7 +552,7 @@ void pk__mark_value(py_TValue* val) {
 }
 
 void pk__mark_namedict(NameDict* dict) {
-    for(int i = 0; i < dict->count; i++) {
+    for(int i = 0; i < dict->length; i++) {
         NameDict_KV* kv = c11__at(NameDict_KV, dict, i);
         pk__mark_value(&kv->value);
     }
@@ -589,7 +589,7 @@ void CodeObject__gc_mark(const CodeObject* self) {
 void ManagedHeap__mark(ManagedHeap* self) {
     VM* vm = self->vm;
     // mark heap objects
-    for(int i = 0; i < self->no_gc.count; i++) {
+    for(int i = 0; i < self->no_gc.length; i++) {
         PyObject* obj = c11__getitem(PyObject*, &self->no_gc, i);
         mark_object(obj);
     }
@@ -599,7 +599,7 @@ void ManagedHeap__mark(ManagedHeap* self) {
     }
     // mark magic slots
     py_TypeInfo* types = vm->types.data;
-    int types_length = vm->types.count;
+    int types_length = vm->types.length;
     // 0-th type is placeholder
     for(int i = 1; i < types_length; i++) {
         for(int j = 0; j <= __missing__; j++) {
diff --git a/src/modules/dis.c b/src/modules/dis.c
index 69a706a6..def8b0ed 100644
--- a/src/modules/dis.c
+++ b/src/modules/dis.c
@@ -8,7 +8,7 @@
 static void disassemble(CodeObject* co) {
     c11_vector /*T=int*/ jumpTargets;
     c11_vector__ctor(&jumpTargets, sizeof(int));
-    for(int i = 0; i < co->codes.count; i++) {
+    for(int i = 0; i < co->codes.length; i++) {
         Bytecode* bc = c11__at(Bytecode, &co->codes, i);
         if(Bytecode__is_forward_jump(bc)) {
             int target = (int16_t)bc->arg + i;
@@ -20,7 +20,7 @@ static void disassemble(CodeObject* co) {
     c11_sbuf__ctor(&ss);
 
     int prev_line = -1;
-    for(int i = 0; i < co->codes.count; i++) {
+    for(int i = 0; i < co->codes.length; i++) {
         Bytecode byte = c11__getitem(Bytecode, &co->codes, i);
         BytecodeEx ex = c11__getitem(BytecodeEx, &co->codes_ex, i);
 
@@ -101,7 +101,7 @@ static void disassemble(CodeObject* co) {
             }
         } while(0);
 
-        if(i != co->codes.count - 1) c11_sbuf__write_char(&ss, '\n');
+        if(i != co->codes.length - 1) c11_sbuf__write_char(&ss, '\n');
     }
 
     c11_string* output = c11_sbuf__submit(&ss);
@@ -115,12 +115,12 @@ static bool dis_dis(int argc, py_Ref argv) {
     PY_CHECK_ARGC(1);
 
     CodeObject* code = NULL;
-    if(py_istype(argv, tp_function)){
+    if(py_istype(argv, tp_function)) {
         Function* ud = py_touserdata(argv);
         code = &ud->decl->code;
-    }else if(py_istype(argv, tp_code)){
+    } else if(py_istype(argv, tp_code)) {
         code = py_touserdata(argv);
-    }else{
+    } else {
         return TypeError("dis() expected a code object");
     }
     disassemble(code);
diff --git a/src/objects/codeobject.c b/src/objects/codeobject.c
index 7c005b83..8a39eba9 100644
--- a/src/objects/codeobject.c
+++ b/src/objects/codeobject.c
@@ -152,7 +152,7 @@ void CodeObject__dtor(CodeObject* self) {
 
     c11_vector__dtor(&self->blocks);
 
-    for(int i = 0; i < self->func_decls.count; i++) {
+    for(int i = 0; i < self->func_decls.length; i++) {
         FuncDecl_ decl = c11__getitem(FuncDecl_, &self->func_decls, i);
         PK_DECREF(decl);
     }
@@ -173,7 +173,7 @@ int CodeObject__add_varname(CodeObject* self, py_Name name) {
     if(index >= 0) return index;
     c11_vector__push(uint16_t, &self->varnames, name);
     self->nlocals++;
-    index = self->varnames.count - 1;
+    index = self->varnames.length - 1;
     c11_smallmap_n2i__set(&self->varnames_inv, name, index);
     return index;
 }
diff --git a/src/public/modules.c b/src/public/modules.c
index 613b5b93..f3aa451f 100644
--- a/src/public/modules.c
+++ b/src/public/modules.c
@@ -85,7 +85,7 @@ int py_import(const char* path_cstr) {
 
         c11_vector /* T=c11_sv */ cpnts = c11_sv__split(package_sv, '.');
         for(int i = is_init; i < dot_count; i++) {
-            if(cpnts.count == 0)
+            if(cpnts.length == 0)
                 return ImportError("attempted relative import beyond top-level package");
             c11_vector__pop(&cpnts);
         }
@@ -98,7 +98,7 @@ int py_import(const char* path_cstr) {
         // join cpnts
         c11_sbuf buf;
         c11_sbuf__ctor(&buf);
-        for(int i = 0; i < cpnts.count; i++) {
+        for(int i = 0; i < cpnts.length; i++) {
             if(i > 0) c11_sbuf__write_char(&buf, '.');
             c11_sbuf__write_sv(&buf, c11__getitem(c11_sv, &cpnts, i));
         }
@@ -616,9 +616,9 @@ static void function__gc_mark(void* ud) {
 static bool function__doc__(int argc, py_Ref argv) {
     PY_CHECK_ARGC(1);
     Function* func = py_touserdata(py_arg(0));
-    if(func->decl->docstring){
+    if(func->decl->docstring) {
         py_newstr(py_retval(), func->decl->docstring);
-    }else{
+    } else {
         py_newnone(py_retval());
     }
     return true;
diff --git a/src/public/py_dict.c b/src/public/py_dict.c
index 6582e085..1c6ab3e4 100644
--- a/src/public/py_dict.c
+++ b/src/public/py_dict.c
@@ -79,7 +79,7 @@ static void Dict__rehash_2x(Dict* self) {
     do {
         Dict__ctor(self, new_capacity);
 
-        for(int i = 0; i < old_dict.entries.count; i++) {
+        for(int i = 0; i < old_dict.entries.length; i++) {
             DictEntry* entry = c11__at(DictEntry, &old_dict.entries, i);
             if(py_isnil(&entry->key)) continue;
             int idx = entry->hash & (new_capacity - 1);
@@ -89,7 +89,7 @@ static void Dict__rehash_2x(Dict* self) {
                 if(idx2 == -1) {
                     // insert new entry (empty slot)
                     c11_vector__push(DictEntry, &self->entries, *entry);
-                    self->indices[idx]._[i] = self->entries.count - 1;
+                    self->indices[idx]._[i] = self->entries.length - 1;
                     self->length++;
                     success = true;
                     break;
@@ -108,10 +108,10 @@ static void Dict__rehash_2x(Dict* self) {
 }
 
 static void Dict__compact_entries(Dict* self) {
-    int* mappings = malloc(self->entries.count * sizeof(int));
+    int* mappings = malloc(self->entries.length * sizeof(int));
 
     int n = 0;
-    for(int i = 0; i < self->entries.count; i++) {
+    for(int i = 0; i < self->entries.length; i++) {
         DictEntry* entry = c11__at(DictEntry, &self->entries, i);
         if(py_isnil(&entry->key)) continue;
         mappings[i] = n;
@@ -121,7 +121,7 @@ static void Dict__compact_entries(Dict* self) {
         }
         n++;
     }
-    self->entries.count = n;
+    self->entries.length = n;
     // update indices
     for(int i = 0; i < self->capacity; i++) {
         for(int j = 0; j < PK_DICT_MAX_COLLISION; j++) {
@@ -145,7 +145,7 @@ static bool Dict__set(Dict* self, py_TValue* key, py_TValue* val) {
             new_entry->hash = hash;
             new_entry->key = *key;
             new_entry->val = *val;
-            self->indices[idx]._[i] = self->entries.count - 1;
+            self->indices[idx]._[i] = self->entries.length - 1;
             self->length++;
             return true;
         }
@@ -179,7 +179,7 @@ static int Dict__pop(Dict* self, py_Ref key) {
             py_newnil(&entry->key);
             self->indices[idx]._[i] = -1;
             self->length--;
-            if(self->length < self->entries.count / 2) Dict__compact_entries(self);
+            if(self->length < self->entries.length / 2) Dict__compact_entries(self);
             return 1;
         }
         if(res == -1) return -1;  // error
@@ -189,7 +189,7 @@ static int Dict__pop(Dict* self, py_Ref key) {
 
 static void DictIterator__ctor(DictIterator* self, Dict* dict) {
     self->curr = dict->entries.data;
-    self->end = self->curr + dict->entries.count;
+    self->end = self->curr + dict->entries.length;
 }
 
 static DictEntry* DictIterator__next(DictIterator* self) {
@@ -291,7 +291,7 @@ static bool dict__repr__(int argc, py_Ref argv) {
     c11_sbuf__ctor(&buf);
     c11_sbuf__write_char(&buf, '{');
     bool is_first = true;
-    for(int i = 0; i < self->entries.count; i++) {
+    for(int i = 0; i < self->entries.length; i++) {
         DictEntry* entry = c11__at(DictEntry, &self->entries, i);
         if(py_isnil(&entry->key)) continue;
         if(!is_first) c11_sbuf__write_cstr(&buf, ", ");
@@ -377,7 +377,7 @@ static bool dict_update(int argc, py_Ref argv) {
     PY_CHECK_ARG_TYPE(1, tp_dict);
     Dict* self = py_touserdata(argv);
     Dict* other = py_touserdata(py_arg(1));
-    for(int i = 0; i < other->entries.count; i++) {
+    for(int i = 0; i < other->entries.length; i++) {
         DictEntry* entry = c11__at(DictEntry, &other->entries, i);
         if(py_isnil(&entry->key)) continue;
         if(!Dict__set(self, &entry->key, &entry->val)) return false;
@@ -449,7 +449,7 @@ static bool dict_values(int argc, py_Ref argv) {
 
 static void dict__gc_mark(void* ud) {
     Dict* self = ud;
-    for(int i = 0; i < self->entries.count; i++) {
+    for(int i = 0; i < self->entries.length; i++) {
         DictEntry* entry = c11__at(DictEntry, &self->entries, i);
         if(py_isnil(&entry->key)) continue;
         pk__mark_value(&entry->key);
@@ -550,7 +550,7 @@ int py_dict_len(py_Ref self) {
 
 bool py_dict_apply(py_Ref self, bool (*f)(py_Ref, py_Ref, void*), void* ctx) {
     Dict* ud = py_touserdata(self);
-    for(int i = 0; i < ud->entries.count; i++) {
+    for(int i = 0; i < ud->entries.length; i++) {
         DictEntry* entry = c11__at(DictEntry, &ud->entries, i);
         if(py_isnil(&entry->key)) continue;
         if(!f(&entry->key, &entry->val, ctx)) return false;
diff --git a/src/public/py_exception.c b/src/public/py_exception.c
index 2096831d..3a3de884 100644
--- a/src/public/py_exception.c
+++ b/src/public/py_exception.c
@@ -33,7 +33,7 @@ int py_BaseException__get_lineno(py_Ref self, const CodeObject* code) {
 
 void py_BaseException__stpush(py_Ref self, SourceData_ src, int lineno, const char* func_name) {
     BaseException* ud = py_touserdata(self);
-    if(ud->stacktrace.count >= 7) return;
+    if(ud->stacktrace.length >= 7) return;
     BaseExceptionFrame* frame = c11_vector__emplace(&ud->stacktrace);
     PK_INCREF(src);
     frame->src = src;
@@ -156,7 +156,7 @@ static void c11_sbuf__write_exc(c11_sbuf* self, py_Ref exc) {
 
     BaseException* ud = py_touserdata(exc);
 
-    for(int i = ud->stacktrace.count - 1; i >= 0; i--) {
+    for(int i = ud->stacktrace.length - 1; i >= 0; i--) {
         BaseExceptionFrame* frame = c11__at(BaseExceptionFrame, &ud->stacktrace, i);
         SourceData__snapshot(frame->src,
                              self,
diff --git a/src/public/py_list.c b/src/public/py_list.c
index 2b0c3521..2dafd0fb 100644
--- a/src/public/py_list.c
+++ b/src/public/py_list.c
@@ -16,7 +16,7 @@ void py_newlistn(py_Ref out, int n) {
     py_newlist(out);
     List* ud = py_touserdata(out);
     c11_vector__reserve(ud, n);
-    ud->count = n;
+    ud->length = n;
 }
 
 py_Ref py_list_data(py_Ref self) {
@@ -41,7 +41,7 @@ void py_list_delitem(py_Ref self, int i) {
 
 int py_list_len(py_Ref self) {
     List* ud = py_touserdata(self);
-    return ud->count;
+    return ud->length;
 }
 
 void py_list_swap(py_Ref self, int i, int j) {
@@ -137,12 +137,12 @@ static bool list__getitem__(int argc, py_Ref argv) {
     py_Ref _1 = py_arg(1);
     if(_1->type == tp_int) {
         int index = py_toint(py_arg(1));
-        if(!pk__normalize_index(&index, self->count)) return false;
+        if(!pk__normalize_index(&index, self->length)) return false;
         *py_retval() = c11__getitem(py_TValue, self, index);
         return true;
     } else if(_1->type == tp_slice) {
         int start, stop, step;
-        bool ok = pk__parse_int_slice(_1, self->count, &start, &stop, &step);
+        bool ok = pk__parse_int_slice(_1, self->length, &start, &stop, &step);
         if(!ok) return false;
         py_newlist(py_retval());
         List* list = py_touserdata(py_retval());
@@ -160,7 +160,7 @@ static bool list__setitem__(int argc, py_Ref argv) {
     PY_CHECK_ARG_TYPE(1, tp_int);
     List* self = py_touserdata(py_arg(0));
     int index = py_toint(py_arg(1));
-    if(!pk__normalize_index(&index, self->count)) return false;
+    if(!pk__normalize_index(&index, self->length)) return false;
     c11__setitem(py_TValue, self, index, *py_arg(2));
     py_newnone(py_retval());
     return true;
@@ -171,7 +171,7 @@ static bool list__delitem__(int argc, py_Ref argv) {
     PY_CHECK_ARG_TYPE(1, tp_int);
     List* self = py_touserdata(py_arg(0));
     int index = py_toint(py_arg(1));
-    if(!pk__normalize_index(&index, self->count)) return false;
+    if(!pk__normalize_index(&index, self->length)) return false;
     c11_vector__erase(py_TValue, self, index);
     py_newnone(py_retval());
     return true;
@@ -186,8 +186,8 @@ static bool list__add__(int argc, py_Ref argv) {
         List* list_1 = py_touserdata(_1);
         py_newlist(py_retval());
         List* list = py_touserdata(py_retval());
-        c11_vector__extend(py_TValue, list, list_0->data, list_0->count);
-        c11_vector__extend(py_TValue, list, list_1->data, list_1->count);
+        c11_vector__extend(py_TValue, list, list_0->data, list_0->length);
+        c11_vector__extend(py_TValue, list, list_1->data, list_1->length);
     } else {
         py_newnotimplemented(py_retval());
     }
@@ -204,7 +204,7 @@ static bool list__mul__(int argc, py_Ref argv) {
         List* list = py_touserdata(py_retval());
         List* list_0 = py_touserdata(_0);
         for(int i = 0; i < n; i++) {
-            c11_vector__extend(py_TValue, list, list_0->data, list_0->count);
+            c11_vector__extend(py_TValue, list, list_0->data, list_0->length);
         }
     } else {
         py_newnotimplemented(py_retval());
@@ -226,7 +226,7 @@ static bool list__repr__(int argc, py_Ref argv) {
     c11_sbuf buf;
     c11_sbuf__ctor(&buf);
     c11_sbuf__write_char(&buf, '[');
-    for(int i = 0; i < self->count; i++) {
+    for(int i = 0; i < self->length; i++) {
         py_TValue* val = c11__at(py_TValue, self, i);
         bool ok = py_repr(val);
         if(!ok) {
@@ -234,7 +234,7 @@ static bool list__repr__(int argc, py_Ref argv) {
             return false;
         }
         c11_sbuf__write_sv(&buf, py_tosv(py_retval()));
-        if(i != self->count - 1) c11_sbuf__write_cstr(&buf, ", ");
+        if(i != self->length - 1) c11_sbuf__write_cstr(&buf, ", ");
     }
     c11_sbuf__write_char(&buf, ']');
     c11_sbuf__py_submit(&buf, py_retval());
@@ -246,7 +246,7 @@ static bool list_extend(int argc, py_Ref argv) {
     List* self = py_touserdata(py_arg(0));
     PY_CHECK_ARG_TYPE(1, tp_list);
     List* other = py_touserdata(py_arg(1));
-    c11_vector__extend(py_TValue, self, other->data, other->count);
+    c11_vector__extend(py_TValue, self, other->data, other->length);
     py_newnone(py_retval());
     return true;
 }
@@ -275,7 +275,7 @@ static bool list_copy(int argc, py_Ref argv) {
     py_newlist(py_retval());
     List* self = py_touserdata(py_arg(0));
     List* list = py_touserdata(py_retval());
-    c11_vector__extend(py_TValue, list, self->data, self->count);
+    c11_vector__extend(py_TValue, list, self->data, self->length);
     return true;
 }
 
@@ -330,8 +330,8 @@ static bool list_pop(int argc, py_Ref argv) {
         return TypeError("pop() takes at most 2 arguments");
     }
     List* self = py_touserdata(py_arg(0));
-    if(self->count == 0) return IndexError("pop from empty list");
-    if(!pk__normalize_index(&index, self->count)) return false;
+    if(self->length == 0) return IndexError("pop from empty list");
+    if(!pk__normalize_index(&index, self->length)) return false;
     *py_retval() = c11__getitem(py_TValue, self, index);
     c11_vector__erase(py_TValue, self, index);
     return true;
@@ -342,9 +342,9 @@ static bool list_insert(int argc, py_Ref argv) {
     PY_CHECK_ARG_TYPE(1, tp_int);
     List* self = py_touserdata(py_arg(0));
     int index = py_toint(py_arg(1));
-    if(index < 0) index += self->count;
+    if(index < 0) index += self->length;
     if(index < 0) index = 0;
-    if(index > self->count) index = self->count;
+    if(index > self->length) index = self->length;
     c11_vector__insert(py_TValue, self, index, *py_arg(2));
     py_newnone(py_retval());
     return true;
@@ -380,7 +380,7 @@ static bool list_sort(int argc, py_Ref argv) {
     if(py_isnone(key)) key = NULL;
 
     bool ok = c11__stable_sort(self->data,
-                               self->count,
+                               self->length,
                                sizeof(py_TValue),
                                (int (*)(const void*, const void*, void*))lt_with_key,
                                key);
@@ -405,7 +405,7 @@ static bool list__contains__(int argc, py_Ref argv) {
 
 static void list__gc_mark(void* ud) {
     List* self = ud;
-    for(int i = 0; i < self->count; i++) {
+    for(int i = 0; i < self->length; i++) {
         pk__mark_value(c11__at(py_TValue, self, i));
     }
 }
diff --git a/src/public/py_mappingproxy.c b/src/public/py_mappingproxy.c
index 5257736e..b5db66fd 100644
--- a/src/public/py_mappingproxy.c
+++ b/src/public/py_mappingproxy.c
@@ -52,8 +52,8 @@ static bool namedict_items(int argc, py_Ref argv) {
     PY_CHECK_ARGC(1);
     py_Ref object = py_getslot(argv, 0);
     NameDict* dict = PyObject__dict(object->_obj);
-    py_newtuple(py_retval(), dict->count);
-    for(int i = 0; i < dict->count; i++) {
+    py_newtuple(py_retval(), dict->length);
+    for(int i = 0; i < dict->length; i++) {
         py_Ref slot = py_tuple_getitem(py_retval(), i);
         py_newtuple(slot, 2);
         NameDict_KV* kv = c11__at(NameDict_KV, dict, i);
diff --git a/src/public/py_str.c b/src/public/py_str.c
index 97430dab..856f0b72 100644
--- a/src/public/py_str.c
+++ b/src/public/py_str.c
@@ -318,8 +318,8 @@ static bool str_split(int argc, py_Ref argv) {
         c11_sv sep = c11_string__sv(py_touserdata(&argv[1]));
         res = c11_sv__split2(self, sep);
     }
-    py_newlistn(py_retval(), res.count);
-    for(int i = 0; i < res.count; i++) {
+    py_newlistn(py_retval(), res.length);
+    for(int i = 0; i < res.length; i++) {
         c11_sv item = c11__getitem(c11_sv, &res, i);
         py_newstrn(py_list_getitem(py_retval(), i), item.data, item.size);
     }
@@ -563,8 +563,8 @@ static bool bytes__getitem__(int argc, py_Ref argv) {
         for(int i = start; step > 0 ? i < stop : i > stop; i += step) {
             c11_vector__push(unsigned char, &res, data[i]);
         }
-        unsigned char* p = py_newbytes(py_retval(), res.count);
-        memcpy(p, res.data, res.count);
+        unsigned char* p = py_newbytes(py_retval(), res.length);
+        memcpy(p, res.data, res.length);
         c11_vector__dtor(&res);
         return true;
     } else {
diff --git a/src/public/values.c b/src/public/values.c
index 9a57365b..882f26e6 100644
--- a/src/public/values.c
+++ b/src/public/values.c
@@ -86,7 +86,7 @@ py_Name
     CodeObject code;
     SourceData_ source = SourceData__rcnew(buffer, "<bind>", EXEC_MODE, false);
     Error* err = pk_compile(source, &code);
-    if(err || code.func_decls.count != 1) {
+    if(err || code.func_decls.length != 1) {
         c11__abort("py_newfunction(): invalid signature '%s'", sig);
     }
     FuncDecl_ decl = c11__getitem(FuncDecl_, &code.func_decls, 0);