diff --git a/include/ustring.h b/include/ustring.h
index bb82464..5367925 100644
--- a/include/ustring.h
+++ b/include/ustring.h
@@ -30,9 +30,7 @@ struct _ustring
 {
     // -------------------- private --------------------
     arraylist_t _alist;
-
     bool is_view;
-
     bool _sorted;
 
     struct _iterator _iter;
@@ -40,9 +38,9 @@ struct _ustring
 
     // -------------------- public --------------------
     // char operations
-    bool (*set)(struct _ustring *self, size_t index, const char c); // O(1)
-    bool (*get)(struct _ustring *self, size_t index, char *c);      // O(1)
-    char (*at)(struct _ustring *self, size_t index);                // O(1)
+    bool (*set)(struct _ustring *self, size_t index, const char c);     // O(1)
+    bool (*get)(struct _ustring *self, size_t index, char *c);          // O(1)
+    const char* (*at)(struct _ustring *self, size_t index);             // O(1)
 
     // base
     bool (*reserve)(struct _ustring *self, size_t capacity);
@@ -108,13 +106,13 @@ struct _ustring
     bool (*format)(struct _ustring *self, const char *format);
 
     // compare
-    int (*eq)(struct _ustring *self, struct _ustring *other);
-    int (*ne)(struct _ustring *self, struct _ustring *other);
-    int (*lt)(struct _ustring *self, struct _ustring *other);
-    int (*le)(struct _ustring *self, struct _ustring *other);
-    int (*gt)(struct _ustring *self, struct _ustring *other);
-    int (*ge)(struct _ustring *self, struct _ustring *other);
-    int (*cmp)(struct _ustring *self, struct _ustring *other);
+    int (*eq)(struct _ustring *self, uview_t v);
+    int (*ne)(struct _ustring *self, uview_t v);
+    int (*lt)(struct _ustring *self, uview_t v);
+    int (*le)(struct _ustring *self, uview_t v);
+    int (*gt)(struct _ustring *self, uview_t v);
+    int (*ge)(struct _ustring *self, uview_t v);
+    int (*cmp)(struct _ustring *self, uview_t v);
 
     // iter
     iterator_t (*iter)(struct _ustring *self, linear_order_t order);
diff --git a/src/darray.c b/src/darray.c
index 6e757f3..ce34979 100644
--- a/src/darray.c
+++ b/src/darray.c
@@ -421,6 +421,7 @@ static bool darray_init(struct _darray *self, size_t obj_size, size_t capacity)
     self->search = darry_search;
 
     // -------------------- default --------------------
+    self->compare = compare_char;
     self->print_obj = default_print_obj;
 
     // -------------------- debug --------------------
diff --git a/src/ustring.c b/src/ustring.c
index 4c33d6f..42d2d54 100644
--- a/src/ustring.c
+++ b/src/ustring.c
@@ -143,11 +143,11 @@ static bool ustring_get(struct _ustring *self, size_t index, char *c)
     return self->_alist->get(self->_alist, index, &c);
 }
 
-static char ustring_at(struct _ustring *self, size_t index)
+static const char* ustring_at(struct _ustring *self, size_t index)
 {
     unicstl_assert(self != NULL);
     unicstl_assert(self->_alist != NULL);
-    return *(char *)self->_alist->at(self->_alist, index);
+    return self->_alist->at(self->_alist, index);
 }
 
 bool ustring_iter_hasnext(struct _iterator *iter)
@@ -473,6 +473,60 @@ static bool ustring_strip_right(struct _ustring *self)
     return true;
 }
 
+int ustring_cmp(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    // size_t min = self->len(self) < v.len ? self->len(self) : v.len;
+    // for (size_t i = 0; i < min; i++)
+    // {
+    //     const char *a = (const char *)self->at(self, i);
+    //     if (*a != v.str[i])
+    //     {
+    //         return *(char*)self->at(self, i) - v.str[i];
+    //     }
+    // }
+    log_debug("self[%d]:%s, v.str[%d]:%s", self->len(self), self->at(self, 0), v.len, v.str);
+
+    size_t max = self->len(self) > v.len ? self->len(self) : v.len;
+    return strncmp(self->at(self, 0), v.str, max);
+}
+
+int ustring_eq(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) == 0;
+}
+
+int ustring_ne(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) != 0;
+}
+
+int ustring_lt(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) < 0;
+}
+
+int ustring_le(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) <= 0;
+}
+
+int ustring_gt(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) > 0;
+}
+
+int ustring_ge(struct _ustring *self, uview_t v)
+{
+    unicstl_assert(self != NULL);
+    return self->cmp(self, v) >= 0;
+}
+
 static bool ustring_init(struct _ustring *self, uview_t view, bool is_view)
 {
     unicstl_assert(self != NULL);
@@ -534,6 +588,14 @@ static bool ustring_init(struct _ustring *self, uview_t view, bool is_view)
     self->strip_left = ustring_strip_left;
     self->strip_right = ustring_strip_right;
 
+    self->eq = ustring_eq;
+    self->ne = ustring_ne;
+    self->lt = ustring_lt;
+    self->le = ustring_le;
+    self->gt = ustring_gt;
+    self->ge = ustring_ge;
+    self->cmp = ustring_cmp;
+    
     // -------------------- default --------------------
     self->print_obj = uprint_char;
 
diff --git a/test/test_ustring.c b/test/test_ustring.c
index 3ae70d7..9b461a9 100644
--- a/test/test_ustring.c
+++ b/test/test_ustring.c
@@ -183,6 +183,24 @@ void test_ustring_append(void)
     ustring_free(&str2);
 }
 
+void test_ustring_cmp(void)
+{
+    ustring_t str = ustring_new_fromcstr("unicstl");
+    TEST_ASSERT_TRUE(str->eq(str, uv("unicstl")));
+    TEST_ASSERT_TRUE(str->ne(str, uv("unicstl1")));
+
+    TEST_ASSERT_FALSE(str->eq(str, uv("")));
+    TEST_ASSERT_TRUE(str->ne(str, uv("")));
+
+    TEST_ASSERT_FALSE(str->eq(str, uv("unicstz")));
+    TEST_ASSERT_FALSE(str->ne(str, uv("unicstl")));
+
+    TEST_ASSERT_TRUE(str->le(str, uv("unicstz")));
+    TEST_ASSERT_TRUE(str->ge(str, uv("unicsta")));
+    TEST_ASSERT_TRUE(str->lt(str, uv("unicstz")));
+    TEST_ASSERT_TRUE(str->gt(str, uv("unicsta")));
+    ustring_free(&str);
+}
 
 void test_ustring(void)
 {
@@ -210,4 +228,6 @@ void test_ustring(void)
     RUN_TEST(test_ustring_strip);
 
     RUN_TEST(test_ustring_append);
+    
+    RUN_TEST(test_ustring_cmp);
 }