diff --git a/src/string.cpp b/src/string.cpp
index ca6fb7f..6fb47aa 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -195,6 +195,89 @@ istring& istring::insert(size_t index, const string_view& str, size_t str_index,
 	return *this;
 }
 
+istring& istring::erase(size_t index, size_t count) {
+	size_t num_after_index = m_size - index;
+	if (count > num_after_index) {
+		count = num_after_index;
+	}
+
+	size_t num_to_move = num_after_index - count;
+	if (num_to_move) {
+		mtl::memmove(m_str + index, m_str + index + count, num_to_move);
+	}
+
+	m_size -= count;
+	m_str[m_size] = '\0';
+
+	return *this;
+}
+
+istring& istring::append(const string_view& str) {
+	size_t space = m_capacity - m_size;
+	size_t count = str.m_size > space ? space : str.m_size;
+
+	mtl::memcpy(m_str + m_size, str.m_str, count);
+
+	m_size += count;
+	m_str[m_size] = '\0';
+
+	return *this;
+}
+
+istring& istring::append(const string_view& str, size_t str_index, size_t count) {
+	size_t space = m_capacity - m_size;
+
+	if (count > space) { count = space; }
+
+	mtl::memcpy(m_str + m_size, str.m_str + str_index, count);
+
+	m_size += count;
+	m_str[m_size] = '\0';
+
+	return *this;
+}
+
+istring& istring::append(size_t count, char ch) {
+	size_t space = m_capacity - m_size;
+
+	if (count > space) { count = space; }
+
+	std::memset(m_str + m_size, ch, count);
+
+	m_size += count;
+	m_str[m_size] = '\0';
+
+	return *this;
+}
+
+istring& istring::operator+=(const string_view& str) {
+	return append(str);
+}
+
+istring& istring::operator+=(char ch) {
+	return append(1, ch);
+}
+
+istring& istring::replace(size_t pos, size_t count, const string_view& str) {
+	size_t space = m_capacity - pos;
+	char* substr = m_str + pos;
+
+	if (str.m_size - count) {
+		size_t space_to_move = space - str.m_size;
+		size_t items_to_move = m_size - count - pos;
+		size_t num_to_move = std::min(items_to_move, space_to_move);
+
+		std::memmove(substr + str.m_size, substr + count, num_to_move);
+	}
+
+	mtl::memcpy(substr, str.m_str, str.m_size);
+
+	m_size += str.m_size - count;
+	m_str[m_size] = '\0';
+	
+	return *this;
+}
+
 void istring::resize(size_t count) {
 	if (count > m_capacity) { count = m_capacity; }
 
@@ -213,6 +296,8 @@ void istring::resize(size_t count, char ch) {
 	m_str[m_size] = '\0';
 }
 
+// ===== search =====
+
 size_t istring::find(const string_view& str, size_t pos) const {
 	if (str.m_size > m_size) { return npos; }