diff --git a/toml/format.hpp b/toml/format.hpp
new file mode 100644
index 0000000..8d131f6
--- /dev/null
+++ b/toml/format.hpp
@@ -0,0 +1,151 @@
+#ifndef TOML11_FORMAT
+#define TOML11_FORMAT
+#include "value.hpp"
+#include <sstream>
+
+namespace toml
+{
+
+template<typename traits = std::char_traits<toml::charactor>,
+         typename alloc = std::allocator<toml::charactor>>
+std::basic_string<toml::charactor, traits, alloc>
+format(const value& v);
+
+template<value_t Type>
+struct format_impl;
+
+template<> struct format_impl<value_t::Boolean>
+{
+    typedef detail::toml_default_type<value_t::Boolean>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        return val ? "true" : "false";
+    }
+};
+
+template<> struct format_impl<value_t::Integer>
+{
+    typedef detail::toml_default_type<value_t::Integer>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        return std::to_string(val);
+    }
+};
+
+template<> struct format_impl<value_t::Float>
+{
+    typedef detail::toml_default_type<value_t::Float>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        std::basic_ostringstream<toml::charactor> oss;
+        oss << std::showpoint << val;
+        if(oss.str().back() == '.') oss << '0';
+        return oss.str();
+    }
+};
+
+template<> struct format_impl<value_t::String>
+{
+    typedef detail::toml_default_type<value_t::String>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        //TODO escape some charactors!
+        return val;
+    }
+};
+
+template<> struct format_impl<value_t::Datetime>
+{
+    typedef detail::toml_default_type<value_t::Datetime>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        std::basic_ostringstream<toml::charactor> oss;
+        oss << val;
+        return oss.str();
+    }
+};
+
+// TODO max length!
+template<> struct format_impl<value_t::Array>
+{
+    typedef detail::toml_default_type<value_t::Array>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        std::basic_string<toml::charactor> retval;
+        retval += '[';
+        for(const auto&& item : val)
+        {
+            retval += format(val);
+            retval += ", ";
+        }
+        retval += ']';
+        return ;
+    }
+};
+
+// TODO max length && inline!
+template<> struct format_impl<value_t::Table>
+{
+    typedef detail::toml_default_type<value_t::Table>::type type;
+
+    static std::basic_string<toml::charactor>
+    invoke(const type& val)
+    {
+        std::basic_string<toml::charactor> retval;
+        for(const auto&& item : val)
+        {
+            retval += val.first;
+            retval += " = "
+            retval += format(val.second);
+            retval += '\n';
+        }
+        return ;
+    }
+};
+
+
+template<typename traits, typename alloc>
+std::basic_string<toml::charactor, traits, alloc>
+format(const value& v)
+{
+    switch(v.type())
+    {
+        case value_t::Boolean : return format_impl<value_t::Boolean >::invoke(v.template cast<value_t::Boolean >());
+        case value_t::Integer : return format_impl<value_t::Integer >::invoke(v.template cast<value_t::Integer >());
+        case value_t::Float   : return format_impl<value_t::Float   >::invoke(v.template cast<value_t::Float   >());
+        case value_t::String  : return format_impl<value_t::String  >::invoke(v.template cast<value_t::String  >());
+        case value_t::Datetime: return format_impl<value_t::Datetime>::invoke(v.template cast<value_t::Datetime>());
+        case value_t::Array   : return format_impl<value_t::Array   >::invoke(v.template cast<value_t::Array   >());
+        case value_t::Table   : return format_impl<value_t::Table   >::invoke(v.template cast<value_t::Table   >());
+        case value_t::Empty   : return format_impl<value_t::Empty   >::invoke(v.template cast<value_t::Empty   >());
+        case value_t::Unknown : return format_impl<value_t::Unknown >::invoke(v.template cast<value_t::Unknown >());
+        default throw std::logic_error("toml::format: unknown enum value");
+    }
+}
+
+template<typename charT = charactor, typename traits = std::char_traits<charT>,
+         typename alloc = std::allocator<charT>>
+std::basic_string<charT, traits, alloc>
+format(std::basic_string<charT, traits, alloc>&& key, const value& val)
+{
+    std::basic_string<charT, traits, alloc> retval(
+            std::forward<std::basic_string<charT, traits, alloc>>(key));
+    retval += " = ";
+    retval += format(val);
+    return retval;
+}
+
+}
+#endif // TOML11_FORMAT