/* Code for exercise 19.1. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/#include <functional>#include <iostream>#include <list>namespace mystd {   template<typename T> inline   void swap(T &a, T &b) {      T tmp(a);      a = b;      b = tmp;   }}namespace mystd {   template<typename Bi> inline   void reverse(Bi begin, Bi end) {      while (begin!=end) {         --end;         if (begin==end)            break;         std::swap(*begin, *end);         ++begin;      }   }}template<typename For>void forward_reverse(For begin1, int len) {   if (len>1) {      int half_len = len/2;      For end1 = begin1; // End of first half      for (int k = 0; k!=half_len; ++k)         ++end1;      For begin2 = end1;      if (len%2!=0) // Odd number of elements?         ++begin2;      std::swap_ranges(begin1, end1, begin2);      forward_reverse(begin1, half_len);      forward_reverse(begin2, half_len);   }}int main() {   std::list<int> L;   int value = 31;   std::cout << "Before reversing: ";   for (int k = 0; k!=10; ++k) {      value = value*13261%1023;      L.push_back(value); // Just some value      std::cout << L.back() << ' ';   }   mystd::reverse(L.begin(), L.end());   std::cout << "\nAfter reversing: ";   for (list<int>::iterator p = L.begin(); p!=L.end(); ++p) {      std::cout << *p << ' ';   }   std::cout << '\n';   forward_reverse(L.begin(), 10);   std::cout << "\nAfter reversing once more: ";   for (list<int>::iterator p = L.begin(); p!=L.end(); ++p) {      std::cout << *p << ' ';   }   std::cout << '\n';   return 0;}