motonacciu

typedef int (*AbsTy)(int);
Reduction<std::plus<int>,AbsTy,AbsTy> r(std::plus<int>(), &abs, &abs);
r(-10, 5); // => 15
r(-2, -4); // => 6

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makeTree(int,bool,std::string) => std::pair<int,std::pair<bool, std::string>>

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template <typename... Args>
???? makeTree(const Args&... args);

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// Termination case (A, B) -> std::pair<A,B>
template <typename LhsTy, typename RhsTy>
std::pair<LhsTy,RhsTy> makeTree(const LhsTy& lhs, const RhsTy& rhs) { 
  return {lhs, rhs}; 
}

template <typename Arg1, typename Arg2, typename Arg3, typename... Args>
auto makeTree(const Arg1& arg1, const Arg2& arg2, const Arg3& arg3, const Args&... args) -> ???
{
  return {arg1, makeTree(arg2,arg3,args...)};

motonacciu

template <typename Arg1, typename Arg2, typename Arg3, typename... Args>
auto makeTree(const Arg1& arg1, const Arg2& arg2, const Arg3& arg3, const Args&... args) -> 
std::pair<Arg1,decltype(makeTree(arg2,arg3,args...))>
{
  return {arg1, makeTree(arg2,arg3,args...)};
}

motonacciu

#include <iostream>

namespace std {
template <typename T1, typename T2>
ostream& operator<<(ostream& out, const pair<T1,T2>& p) {
  return out << "(" << p.first << "," << p.second << ")";
}
} // end std namespace

int main(int argc, char* argv[]) {

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template <size_t N> struct uint_{ };

template <size_t N, typename Lambda, typename IterT>
inline void unroller(const Lambda& f, const IterT& iter, uint_<N>) {
	unroller(f, iter, uint_<N-1>());
	f(iter + N);
}

template <typename Lambda, typename IterT>
inline void unroller(const Lambda& f, const IterT& iter, uint_<0>) {

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std::vector<double> vec(N);

// loop body as a lambda 
auto body = [&](const int& i) { vec[i] = i*(i-1)*4*(i+1); };

assert(vec.size()%UnrollFact == 0 && "Vector size must be divisible by the Unrolling Factor");

auto start = std::chrono::system_clock::now();
for(size_t i = 0, size=vec.size(); i!=size; i+=UnrollFact) {
  unroller( body, i, uint_<UnrollFact-1>() );

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auto start = std::chrono::system_clock::now();
for(size_t i = 0, size=vec.size(); i!=size; ++i) {
	vec[i] = i*(i-1)*4*(i+1);
}
auto end = std::chrono::system_clock::now();

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namespace detail {

template <class IterT>
IterT partition(IterT begin, IterT end) {

    // The pivot is the first element of this array section
    IterT pivotIdx = begin;
    auto pivot = *(begin++);

    while(begin < end){