// Taken from https://gist.github.com/arvidsson/7231973

#ifndef BITCOIN_REVERSE_ITERATOR_H
#define BITCOIN_REVERSE_ITERATOR_H

/**
 * Template used for reverse iteration in C++11 range-based for loops.
 *
 *   std::vector<int> v = {1, 2, 3, 4, 5};
 *   for (auto x : reverse_iterate(v))
 *       std::cout << x << " ";
 */

template <typename T>
class reverse_range
{
    T &m_x;

public:
    reverse_range(T &x) : m_x(x) {}

    auto begin() const -> decltype(this->m_x.rbegin())
    {
        return m_x.rbegin();
    }

    auto end() const -> decltype(this->m_x.rend())
    {
        return m_x.rend();
    }
};

template <typename T>
reverse_range<T> reverse_iterate(T &x)
{
    return reverse_range<T>(x);
}

#endif // BITCOIN_REVERSE_ITERATOR_H

// Taken from https://gist.github.com/arvidsson/7231973

#ifndef BITCOIN_REVERSE_ITERATOR_HPP
#define BITCOIN_REVERSE_ITERATOR_HPP

/**
 * Template used for reverse iteration in C++11 range-based for loops.
 *
 *   std::vector<int> v = {1, 2, 3, 4, 5};
 *   for (auto x : reverse_iterate(v))
 *       std::cout << x << " ";
 */

template <typename T>
class reverse_range
{
    T &x;

public:
    reverse_range(T &x) : x(x) {}

    auto begin() const -> decltype(this->x.rbegin())
    {
        return x.rbegin();
    }

    auto end() const -> decltype(this->x.rend())
    {
        return x.rend();
    }
};

template <typename T>
reverse_range<T> reverse_iterate(T &x)
{
    return reverse_range<T>(x);
}

#endif // BITCOIN_REVERSE_ITERATOR_HPP

--- 
+++ 
@@ -1,7 +1,7 @@
 // Taken from https://gist.github.com/arvidsson/7231973
 
-#ifndef BITCOIN_REVERSE_ITERATOR_HPP
-#define BITCOIN_REVERSE_ITERATOR_HPP
+#ifndef BITCOIN_REVERSE_ITERATOR_H
+#define BITCOIN_REVERSE_ITERATOR_H
 
 /**
  * Template used for reverse iteration in C++11 range-based for loops.
@@ -14,19 +14,19 @@
 template <typename T>
 class reverse_range
 {
-    T &x;
+    T &m_x;
 
 public:
-    reverse_range(T &x) : x(x) {}
+    reverse_range(T &x) : m_x(x) {}
 
-    auto begin() const -> decltype(this->x.rbegin())
+    auto begin() const -> decltype(this->m_x.rbegin())
     {
-        return x.rbegin();
+        return m_x.rbegin();
     }
 
-    auto end() const -> decltype(this->x.rend())
+    auto end() const -> decltype(this->m_x.rend())
     {
-        return x.rend();
+        return m_x.rend();
     }
 };
 
@@ -36,4 +36,4 @@
     return reverse_range<T>(x);
 }
 
-#endif // BITCOIN_REVERSE_ITERATOR_HPP
+#endif // BITCOIN_REVERSE_ITERATOR_H
Rename member field according to the style guide.
