cpp-lazy-stream/streams.cpp

#include <vector>
#include <iostream>
#include <iterator>

#include "streams.hpp"

namespace stream {
  template <typename T, typename F>
  auto make_map_t(F&& func) -> map_t<T, decltype(func(std::declval<T>()))> {
    return map_t<T, decltype(func(std::declval<T>()))>{func};
  }
  
  template <typename T, typename F>
  auto make_flatmap_t(F&& func) -> flatmap_t<T, decltype(func(std::declval<T>()))> {
    return flatmap_t<T, decltype(func(std::declval<T>()))>{func};
  }

  template <typename T, typename F>
  auto make_filter_t(F&& func) -> filter_t<T> {
    return filter_t<T>{func};
  }
}

#define map(t, x, expr) stream::make_map_t<t>([](t x) { return expr; })
#define filter(t, x, expr) stream::make_filter_t<t>([](t x) { return expr; })
#define flatmap(t, x, expr) stream::make_flatmap_t<t>([](t x) { return expr; })
#define fold(t, x, y, expr, init) stream::make_fold_t<t>([](t x, t y) { return expr; })

template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> const& tmp) {
  os << "{ ";
  for (auto it = tmp.begin(); it != tmp.end(); ++it) {
    os << *it << ", ";
  }
  return os << "\b\b }";
}

std::vector<int> iota(int max) {
  std::vector<int> r(3);
  std::iota(r.begin(), r.end(), max);
  return r;
}

int main(int argc, const char**argv) {
  std::vector<int> vec{1,2,3,4,5};
//  auto s = stream::make_stream(vec) | stream::map_t<int, int>([](int x) { return x*2; });
  auto s = stream::make_stream(vec) | filter(int, x, x%2==0) | map(int, x, x*2);
  std::cout << "The result of the expression 'stream(vec) | filter(x,x%2==0) | map(x,x*2)' is:\n\t";
  std::cout << "{ ";
  for (auto it = s.begin(); it != s.end(); ++it) {
    std::cout << *it << ", ";
  }
  std::cout << "\b\b }" << std::endl;
  std::cout << "The result of the expression 'stream(vec) | filter(x,x%2==0) | map(x,x*2) | fold(i,j,i*j,1)' is:\n\t";
  std::cout << s.accumulate([](int i, int j){return i*j;},1);
  std::cout << std::endl;
  auto t = s | flatmap(int, x, std::vector<double>{1/(double)x});
  std::cout << "The result of the expression 'stream(vec) | filter(x,x%2==0) | map(x,x*2) | map(x, [1/x])' is:\n\t";
  std::cout << "{ ";
  for (auto it = t.begin(); it != t.end(); ++it) {
    std::cout << *it << ", ";
  }
  std::cout << "\b\b }" << std::endl;
  auto q = stream::make_stream(vec) | filter(int, x, x%2==1) | map(int, x, iota(x));
  std::cout << "The result of the expression 'stream(vec) | filter(x,x%2==1) | map(x,iota(x))' is:\n\t";
  std::cout << "{ ";
  for (auto it = q.begin(); it != q.end(); ++it) {
    std::cout << *it << ", ";
  }
  std::cout << "\b\b }" << std::endl;
  return 0;
}