diff --git a/include/rexy/string_base.hpp b/include/rexy/string_base.hpp
index 6b13a1a..e0fd748 100644
--- a/include/rexy/string_base.hpp
+++ b/include/rexy/string_base.hpp
@@ -26,6 +26,7 @@
 #include <climits> //CHAR_BIT
 #include <iterator> //reverse_iterator
 #include <iostream> //ostream
+#include <initializer_list>
 
 #include "steal.hpp"
 #include "utility.hpp"
@@ -188,6 +189,9 @@ namespace rexy{
 			else
 				return get_short_length();
 		}
+		constexpr size_type size(void)const noexcept{
+			return length();
+		}
 		constexpr size_type capacity(void)const noexcept{
 			if(islong())
 				return get_long_capacity();
@@ -259,6 +263,8 @@ namespace rexy{
 		using const_reverse_iterator = typename string_base<Char>::const_reverse_iterator;
 		using allocator_type = Alloc;
 
+		static constexpr size_type npos = size_type{-1};
+
 	private:
 		REXY_CPP20_CONSTEXPR void _copy_construct_string(const_pointer data, size_type len, size_type cap)
 			noexcept(is_nothrow_allocator_v<Alloc>);
@@ -302,8 +308,28 @@ namespace rexy{
 		//Replace managed pointer. Frees existing value
 		REXY_CPP20_CONSTEXPR void reset(pointer val = nullptr)noexcept(is_nothrow_allocator_v<Alloc>);
 		REXY_CPP20_CONSTEXPR void reset(pointer val, size_type len)noexcept(is_nothrow_allocator_v<Alloc>);
-		REXY_CPP20_CONSTEXPR bool resize(size_type newsize)
-			noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR bool resize(size_type newsize)noexcept(is_nothrow_allocator_v<Alloc>);
+
+		//TODO more insert
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, size_type insert_count, value_type v)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, value_type v)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, const_pointer str)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, const_pointer str, size_type insert_count)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, const basic_string& other)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, const basic_string& other, size_type index_str, size_type count = npos)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(const_iterator pos, value_type v)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(const_iterator pos, size_type count, value_type v)noexcept(is_nothrow_allocator_v<Alloc>);
+		template<class InIt>
+		REXY_CPP20_CONSTEXPR basic_string& insert(const_iterator pos, InIt start, InIt last)noexcept(is_nothrow_allocator_v<Alloc>);
+		template<class InIt>
+		REXY_CPP20_CONSTEXPR basic_string& insert(size_type pos, InIt start, InIt last)noexcept(is_nothrow_allocator_v<Alloc>);
+		REXY_CPP20_CONSTEXPR basic_string& insert(const_iterator pos, std::initializer_list<value_type> list)noexcept(is_nothrow_allocator_v<Alloc>);
+		template<class StringView>
+		REXY_CPP20_CONSTEXPR auto insert(size_type pos, const StringView& sv)noexcept(is_nothrow_allocator_v<Alloc>) ->
+			std::enable_if_t<std::is_convertible_v<const StringView&, basic_string_view<value_type>> && !std::is_convertible_v<const StringView&,const_pointer>>;
+		template<class StringView>
+		REXY_CPP20_CONSTEXPR auto insert(size_type pos, const StringView& sv, size_type index_str, size_type count = npos)noexcept(is_nothrow_allocator_v<Alloc>) ->
+			std::enable_if_t<std::is_convertible_v<const StringView&, basic_string_view<value_type>> && !std::is_convertible_v<const StringView&,const_pointer>>;
 
 		REXY_CPP20_CONSTEXPR void push_back(value_type data)
 			noexcept(is_nothrow_allocator_v<Alloc>);
@@ -317,6 +343,7 @@ namespace rexy{
 
 		template<REXY_ALLOCATOR_CONCEPT A = allocator_type>
 		REXY_CPP20_CONSTEXPR basic_string<value_type,A> substring(size_type start, size_type end)const;
+		REXY_CPP20_CONSTEXPR basic_string substr(size_type start, size_type end)const;
 
 		REXY_CPP20_CONSTEXPR pointer release(void)noexcept(is_nothrow_allocator_v<Alloc>);
 		using detail::hasallocator<Alloc>::allocator;
diff --git a/include/rexy/string_base.tpp b/include/rexy/string_base.tpp
index 279936c..b86237a 100644
--- a/include/rexy/string_base.tpp
+++ b/include/rexy/string_base.tpp
@@ -250,6 +250,106 @@ namespace rexy{
 		return (*this = basic_string(this->get_pointer(), newsize));
 	}
 
+
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, size_type insert_count, value_type v)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		struct insert_adapter{
+			size_type max;
+			value_type val;
+
+			constexpr insert_adapter& operator++(void)noexcept{
+				--max;
+				return *this;
+			}
+			constexpr value_type operator*(void)const noexcept{
+				return val;
+			}
+
+			constexpr bool operator==(const insert_adapter& other)const = default;
+			constexpr bool operator!=(const insert_adapter& other)const = default;
+		};
+
+		return insert(pos, insert_adapter{insert_count, v}, insert_adapter{0, v});
+	}
+
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, value_type v)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, size_type{1}, v);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const_pointer str)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		const size_type slen = rexy::strlen(str);
+		return insert(pos, str, str + slen);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const_pointer str, size_type insert_count)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, str, str + insert_count);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const basic_string& other)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, other.begin(), other.end());
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const basic_string& other, size_type index_str, size_type count)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, other.begin() + index_str, other.begin() + index_str + count);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(const_iterator pos, value_type v)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, size_type{1}, v);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(const_iterator pos, size_type count, value_type v)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos - this->begin(), count, v);
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	template<class InIt>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(const_iterator pos, InIt start, InIt last)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos - this->begin(), std::move(start), std::move(last));
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(const_iterator pos, std::initializer_list<value_type> list)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		return insert(pos, list.begin(), list.end());
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	template<class StringView>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const StringView& sv)noexcept(is_nothrow_allocator_v<Alloc>) ->
+		std::enable_if_t<std::is_convertible_v<const StringView&, basic_string_view<value_type>> && !std::is_convertible_v<const StringView&,const_pointer>>
+	{
+		return insert(pos, sv.begin(), sv.end());
+	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	template<class StringView>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, const StringView& sv, size_type index_str, size_type count)noexcept(is_nothrow_allocator_v<Alloc>) ->
+		std::enable_if_t<std::is_convertible_v<const StringView&, basic_string_view<value_type>> && !std::is_convertible_v<const StringView&,const_pointer>>
+	{
+		return insert(pos, sv.begin() + index_str, sv.begin() + index_str + count);
+	}
+
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	template<class InIt>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::insert(size_type pos, InIt start, InIt last)noexcept(is_nothrow_allocator_v<Alloc>) -> basic_string&{
+		const size_type len = this->length();
+		size_type insert_count = 0;
+		for(auto it = start;it != last;++it, ++insert_count){}
+		resize(rexy::max(pos + insert_count, len + insert_count));
+
+		const size_type move_count = rexy::min<size_type>(0, len - pos);
+		const auto ptr = this->get_pointer();
+
+		for(size_type i = move_count+1;i > 0;--i){
+			const size_type index = i + pos;
+			ptr[index] = ptr[index-1];
+		}
+		{
+			size_type i = 0;
+			for(auto it = start;it != last;++it,++i){
+				ptr[pos+i] = *it;
+			}
+		}
+		this->set_length(len + insert_count);
+		return *this;
+	}
+
 	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
 	REXY_CPP20_CONSTEXPR void basic_string<Char,Alloc>::push_back(value_type data)
 		noexcept(is_nothrow_allocator_v<Alloc>)
@@ -320,6 +420,11 @@ namespace rexy{
 		tmp.append(this->get() + start, newlen);
 		return tmp;
 	}
+	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
+	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::substr(size_type start, size_type end)const -> basic_string{
+		return substring<allocator_type>(start, end);
+	}
+
 	template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
 	REXY_CPP20_CONSTEXPR auto basic_string<Char,Alloc>::release(void)noexcept(is_nothrow_allocator_v<Alloc>) -> pointer{
 		if(this->islong()){