diff --git a/toml/region.hpp b/toml/region.hpp
index 355c785..20bdda8 100644
--- a/toml/region.hpp
+++ b/toml/region.hpp
@@ -1,9 +1,9 @@
 #ifndef TOML11_REGION_H
 #define TOML11_REGION_H
+#include "exception.hpp"
 #include <memory>
 #include <algorithm>
 #include <iterator>
-#include <string>
 
 namespace toml
 {
@@ -18,19 +18,32 @@ struct location
 {
     static_assert(std::is_same<char, typename Container::value_type>::value,"");
     using const_iterator = typename Container::const_iterator;
+    using source_ptr     = std::shared_ptr<const Container>;
 
     location(Container cont)
-      : source(std::make_shared<Container>(std::move(cont))),
-        begin(source->cbegin()), iter(source->cbegin()), end(source->cend())
+      : source_(std::make_shared<Container>(std::move(cont))),
+        begin_(source_->cbegin()), iter_(source_->cbegin()),
+        end_(source_->cend())
     {}
     location(const location&) = default;
     location(location&&)      = default;
     location& operator=(const location&) = default;
     location& operator=(location&&)      = default;
-   ~location() = default;
+    ~location() = default;
 
-    std::shared_ptr<const Container> source;
-    const_iterator begin, iter, end;
+    const_iterator& iter()       noexcept {return iter_;}
+    const_iterator  iter() const noexcept {return iter_;}
+
+    const_iterator  begin() const noexcept {return begin_;}
+    const_iterator  end()   const noexcept {return end_;}
+
+    source_ptr const& source() const& noexcept {return source_;}
+    source_ptr&&      source() &&     noexcept {return std::move(source_);}
+
+  private:
+
+    source_ptr source_;
+    const_iterator begin_, iter_, end_;
 };
 
 // region in a container, normally in a file content.
@@ -42,23 +55,24 @@ struct region
 {
     static_assert(std::is_same<char, typename Container::value_type>::value,"");
     using const_iterator = typename Container::const_iterator;
+    using source_ptr     = std::shared_ptr<const Container>;
 
     region(const location<Container>& loc)
-      : begin(loc.begin), first(loc.iter), last(loc.iter), end(loc.end),
-        source(loc.source)
+      : begin_(loc.begin()), first_(loc.iter()),
+        last_(loc.iter()), end_(loc.end()), source_(loc.source())
     {}
     region(location<Container>&& loc)
-      : begin(loc.begin), first(loc.iter), last(loc.iter), end(loc.end),
-        source(std::move(loc.source))
+      : begin_(loc.begin()), first_(loc.iter()),
+        last_(loc.iter()), end_(loc.end()), source_(std::move(loc.source()))
     {}
 
     region(const location<Container>& loc, const_iterator f, const_iterator l)
-      : begin(loc.begin), first(f), last(l), end(loc.end),
-        source(loc.source)
+      : begin_(loc.begin()), first_(f), last_(l), end_(loc.end()),
+        source_(loc.source())
     {}
     region(location<Container>&& loc, const_iterator f, const_iterator l)
-      : begin(loc.begin), first(f), last(l), end(loc.end),
-        source(std::move(loc.source))
+      : begin_(loc.begin()), first_(f), last_(l), end_(loc.end()),
+        source_(std::move(loc.source()))
     {}
 
     region(const region&) = default;
@@ -67,11 +81,32 @@ struct region
     region& operator=(region&&)      = default;
     ~region() = default;
 
-    std::string str()  const {return std::string(first, last);}
-    std::size_t size() const {return std::distance(first, last);}
+    region& operator+=(const region& other)
+    {
+        if(this->begin_ != other.begin_ || this->end_ != other.end_ ||
+           this->last_  != other.first_)
+        {
+            throw internal_error("invalid region concatenation");
+        }
+        this->last_ = other.last_;
+        return *this;
+    }
 
-    const_iterator begin, first, last, end;
-    std::shared_ptr<const Container> source;
+    std::string str()  const {return std::string(first_, last_);}
+    std::size_t size() const {return std::distance(first_, last_);}
+
+    const_iterator  begin() const noexcept {return begin_;}
+    const_iterator  end()   const noexcept {return end_;}
+    const_iterator  first() const noexcept {return first_;}
+    const_iterator  last()  const noexcept {return last_;}
+
+    source_ptr const& source() const& noexcept {return source_;}
+    source_ptr&&      source() &&     noexcept {return std::move(source_);}
+
+  private:
+
+    const_iterator begin_, first_, last_, end_;
+    source_ptr source_;
 };
 
 // to show a better error message.
@@ -82,13 +117,13 @@ format_underline(const region<Container>& reg, const std::string& msg)
     using const_iterator = typename region<Container>::const_iterator;
     using reverse_iterator = std::reverse_iterator<const_iterator>;
     const auto line_begin = std::find(
-            reverse_iterator(reg.first),
-            reverse_iterator(reg.begin),
+            reverse_iterator(reg.first()),
+            reverse_iterator(reg.begin()),
             '\n').base();
-    const auto line_end = std::find(reg.last, reg.end, '\n');
+    const auto line_end = std::find(reg.last(), reg.end(), '\n');
 
     const auto line_number = std::to_string(
-            1 + std::count(reg.begin, reg.first, '\n'));
+            1 + std::count(reg.begin(), reg.first(), '\n'));
 
     std::string retval;
     retval += ' ';
@@ -98,8 +133,8 @@ format_underline(const region<Container>& reg, const std::string& msg)
     retval += '\n';
     retval += std::string(line_number.size() + 1, ' ');
     retval += " | ";
-    retval += std::string(std::distance(line_begin, reg.first), ' ');
-    retval += std::string(std::distance(reg.first, reg.last), '~');
+    retval += std::string(std::distance(line_begin, reg.first()), ' ');
+    retval += std::string(std::distance(reg.first(), reg.last()), '~');
     retval += ' ';
     retval += msg;
     return retval;
@@ -114,13 +149,13 @@ std::string format_underline(const region<Container>& reg,
     using const_iterator = typename region<Container>::const_iterator;
     using reverse_iterator = std::reverse_iterator<const_iterator>;
     const auto line_begin = std::find(
-            reverse_iterator(reg.first),
-            reverse_iterator(reg.begin),
+            reverse_iterator(reg.first()),
+            reverse_iterator(reg.begin()),
             '\n').base();
-    const auto line_end = std::find(reg.last, reg.end, '\n');
+    const auto line_end = std::find(reg.last(), reg.end(), '\n');
 
     const auto line_number = std::to_string(
-            1 + std::count(reg.begin, reg.first, '\n'));
+            1 + std::count(reg.begin(), reg.first(), '\n'));
 
     std::string retval;
     retval += ' ';
@@ -130,16 +165,16 @@ std::string format_underline(const region<Container>& reg,
     retval += '\n';
     retval += std::string(line_number.size() + 1, ' ');
     retval += " | ";
-    retval += std::string(std::distance(line_begin, reg.first), ' ');
+    retval += std::string(std::distance(line_begin, reg.first()), ' ');
 
-    if(std::distance(reg.first, std::prev(pos)) > 0)
+    if(std::distance(reg.first(), std::prev(pos)) > 0)
     {
-        retval += std::string(std::distance(reg.first, std::prev(pos)), '-');
+        retval += std::string(std::distance(reg.first(), std::prev(pos)), '-');
     }
     retval += '^';
-    if(std::distance(pos, reg.last) > 0)
+    if(std::distance(pos, reg.last()) > 0)
     {
-        retval += std::string(std::distance(std::next(pos), reg.last), '-');
+        retval += std::string(std::distance(std::next(pos), reg.last()), '-');
     }
 
     retval += ' ';