BoostToStd.cc

#include <tuple>
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <iterator>

/* This is an attempt to translate the Boost-oriented demo of C++14
   from the O'Reilly handout "C++ Today: The Beast Is Back"
   (http://www.oreilly.com/programming/free/files/c++-today.pdf) into
   something both GCC 4.8.5 and Clang 3.9.1 can understand and use
   without Boost.

   A bit got lost in translation; Boost's "iterator_value_type" is a
   loose revision of std::iterator_traits<T>::value_type, and even if
   I am moving the tuple back to the calling space, the tuple type
   can't be auto-cast, which I think was part of the original demo.
   Where they return {count, minimum, maximum}, I had to provide the
   type as a templated typename, which was disappointing, to work
   around the explicit constructor limitations in std::tuple<T...>.

   On the other hand, I was able to exchange the primitive while()
   loop with a lambda, which makes me very happy.  This code actually
   passes both clang-tidy (c++1y mode) and cppcheck (c++11 mode)
   without a single complaint.
*/

template <typename ConstInputIterator,
          typename MinMaxType = typename std::iterator_traits<ConstInputIterator>::value_type,
          typename ResultType = std::tuple<size_t, MinMaxType, MinMaxType>>
auto lenminmax(ConstInputIterator first, ConstInputIterator last) -> ResultType
{
  if (first == last) { return ResultType(0, 0, 0); }
  auto count = size_t{1};
  auto minimum(*first);
  auto maximum(minimum); // only evaluate *first once
  for_each(first, last, [&minimum, &maximum, &count](MinMaxType &value) {
      if (value < minimum) { minimum = value; }
      if (value > maximum) { maximum = value; }
      count++;
  });
  return ResultType(count, minimum, maximum);
}

/* std::tie and std::ignore are provided by std::tuple; std::tie
   allows you to receive multiple return values, and std::ignore tells
   the compiler that a particular return value is of no interest to
   the receiving function.
*/

int main() {
  std::vector<int> samples {5, 3, 2, 4, 8, 9, 13, 12};
  int min, max;
  std::tie(std::ignore, min, max) = lenminmax(samples.begin(), samples.end());
  std::cout << "Minimun: " << min << ", Maximum: " << max << std::endl;
}