diff --git a/bin/main.cpp b/bin/main.cpp
index 3d9fc4e..65c21ce 100644
--- a/bin/main.cpp
+++ b/bin/main.cpp
@@ -2,16 +2,23 @@
 
 #include "string/string.hpp"
 #include "range/range.hpp"
+#include "container/container.hpp"
 
 int main(int argc, char *argv[])
 {
   {// ex: split_str
     std::string str { "asdf,qwer,zxcv" };
-    hack::v_str v = hack::split_str(str, ',');
+    hack::string::v_str v = hack::string::split_str(str, ',');
     for (const auto& c : v) std::cout << c << std::endl;
   }
 
   {// ex: within
-    std::cout << hack::within(12, 34, 12, 23, 31) << std::endl;
+    std::cout << std::boolalpha << hack::range::within(12, 34, 12, 23, 31, 17, 22, 33) << std::endl;
+  }
+  
+  {// ex: v_multiset
+    std::vector<std::string> v;
+    hack::container::v_multiset(v, "asdf", "qwer", "zcv");
+    for(const auto& c : v) std::cout << c << std::endl;
   }
 }
diff --git a/bin/meson.build b/bin/meson.build
index 6baa655..727a5f2 100644
--- a/bin/meson.build
+++ b/bin/meson.build
@@ -1,5 +1,6 @@
 deps += string_dep
 deps += range_dep
+deps += range_dep
 
 executable(
   'hack', 'main.cpp', 
diff --git a/src/container/container.cpp b/src/container/container.cpp
new file mode 100644
index 0000000..b9b67f4
--- /dev/null
+++ b/src/container/container.cpp
@@ -0,0 +1,5 @@
+#include "container.hpp"
+
+namespace hack::container
+{
+}
diff --git a/src/container/container.hpp b/src/container/container.hpp
new file mode 100644
index 0000000..e88e14f
--- /dev/null
+++ b/src/container/container.hpp
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <vector>
+
+namespace hack::container
+{
+  template<typename Range, typename... Args>
+  void v_multiset(Range& r, Args... args)
+  {
+    std::size_t t = sizeof... (args);
+    r.reserve(t);
+    (r.emplace_back(std::forward<Args>(args)), ...);
+  }
+}
diff --git a/src/container/meson.build b/src/container/meson.build
new file mode 100644
index 0000000..29d3539
--- /dev/null
+++ b/src/container/meson.build
@@ -0,0 +1,14 @@
+headers = ['container.hpp']
+sources = ['container.cpp']
+
+lib = library(
+  'container',
+  include_directories : inc,
+  install : true,
+  sources: [headers, sources]
+)
+
+container_dep = declare_dependency(
+  include_directories: inc,
+  link_with: lib
+)
diff --git a/src/meson.build b/src/meson.build
index 325ba16..2e0df30 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -2,3 +2,4 @@ inc += include_directories('.')
 
 subdir('string')
 subdir('range')
+subdir('container')
diff --git a/src/range/range.cpp b/src/range/range.cpp
index 614e456..70dd2e8 100644
--- a/src/range/range.cpp
+++ b/src/range/range.cpp
@@ -1,5 +1,5 @@
 #include "range.hpp"
 
-namespace hack
+namespace hack::renge
 {
 }
diff --git a/src/range/range.hpp b/src/range/range.hpp
index 82c93bb..a91f5fd 100644
--- a/src/range/range.hpp
+++ b/src/range/range.hpp
@@ -1,9 +1,9 @@
 #pragma once
 
-namespace hack
+namespace hack::range
 {
   template<typename T, typename... Args>
-  bool within(T min, T max, Args... args)
+  bool within(const T min, const T max, Args... args)
   {
     return ((min <= args && max >= args) && ...);
     // 1, 5, 2, 3, 4
diff --git a/src/string/string.cpp b/src/string/string.cpp
index df3a2e5..b7c94d2 100644
--- a/src/string/string.cpp
+++ b/src/string/string.cpp
@@ -1,6 +1,6 @@
 #include "string.hpp"
 
-namespace hack
+namespace hack::string
 {
   v_str split_str(const std::string& str, char t)
   {
diff --git a/src/string/string.hpp b/src/string/string.hpp
index 6b4a87a..81d21be 100644
--- a/src/string/string.hpp
+++ b/src/string/string.hpp
@@ -3,7 +3,7 @@
 #include <string>
 #include <vector>
 
-namespace hack
+namespace hack::string
 {
   using v_str = std::vector<std::string>;
 
diff --git a/tests/container.cpp b/tests/container.cpp
new file mode 100644
index 0000000..7895080
--- /dev/null
+++ b/tests/container.cpp
@@ -0,0 +1,10 @@
+#include <gtest/gtest.h>
+
+#include "container/container.hpp"
+
+TEST(v_multiset, check)
+{
+  std::vector<int> v;
+  hack::container::v_multiset(v, 1, 2, 3);
+  ASSERT_EQ(v.at(0), 1);
+}
diff --git a/tests/meson.build b/tests/meson.build
index 9773ccb..24775e3 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -18,3 +18,12 @@ test(
     dependencies: [ range_dep, gtest_dep ]
   )
 )
+
+test(
+  'container',
+  executable(
+    'container',
+    'container.cpp',
+    dependencies: [ range_dep, gtest_dep ]
+  )
+)
diff --git a/tests/range.cpp b/tests/range.cpp
index 10edac8..4066e39 100644
--- a/tests/range.cpp
+++ b/tests/range.cpp
@@ -4,6 +4,6 @@
 
 TEST(within, check)
 {
-  ASSERT_EQ(hack::within(23, 123, 34, 44, 55, 66), true);
-  ASSERT_EQ(hack::within(23, 123, 134, 44, 55, 66), false);
+  ASSERT_EQ(hack::range::within(23, 123, 34, 44, 55, 66), true);
+  ASSERT_EQ(hack::range::within(23, 123, 134, 44, 55, 66), false);
 }
diff --git a/tests/string.cpp b/tests/string.cpp
index e644003..0cffff2 100644
--- a/tests/string.cpp
+++ b/tests/string.cpp
@@ -7,7 +7,6 @@
 
 TEST(split_str, check)
 {
-  hack::v_str v { "asdf", "qwer", "zxcv" };
-
-  ASSERT_EQ(hack::split_str("asdf,qwer,zxcv", ','), v);
+  std::vector<std::string> v { "asdf", "qwer", "zxcv" };
+  ASSERT_EQ(hack::string::split_str("asdf,qwer,zxcv", ','), v);
 }