Examples

• Example 1: Comparison with std::ranges

Compiling the examples

All examples have been compiled on a MacBook Pro with an Apple M2 Max chip. At the point of writing this documentation only gcc has implemented the required std::ranges for some of the examples. We therefore used gcc 15.2.0 together with cmake 4.1.2.

Assuming that the actual example code is in a file main.cpp and that the print.hpp (see below) is in the same directory, the following generic CMakeLists.txt should work for all examples:

cmake_minimum_required(VERSION 3.20)
project(example CXX)
 
# set required standard (needed for some std::ranges)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
# fetch itertools from github
set(Build_Tests OFF CACHE BOOL "" FORCE)
include (FetchContent)
FetchContent_Declare(
  itertools
  GIT_REPOSITORY https://github.com/TRIQS/itertools.git
  GIT_TAG        2.0.x
)
FetchContent_MakeAvailable(itertools)
 
# build the example
add_executable(ex main.cpp)
target_link_libraries(ex itertools::itertools_c)

print.hpp

To print the elements of a range to stdout, we used the following header:

#include <iostream>
#include <tuple>
#include <utility>
 
// helper function to pretty-print a tuple/array
template <typename T, size_t... I> void print_impl(const T &tup, std::index_sequence<I...>) {
  std::cout << "(";
  (..., (std::cout << (I == 0 ? "" : ", ") << std::get<I>(tup)));
  std::cout << ")";
}
 
// print a tuple/array to std::cout
template <typename T> void print_tuple(const T &tup) { print_impl(tup, std::make_index_sequence<std::tuple_size_v<T>>()); }
 
// print a range of tuple elements to std::cout
template <typename R> void print_tuple_range(R &&rg) { // NOLINT (cppcoreguidelines-missing-std-forward)
  for (auto &&x : rg) {
    print_tuple(x);
    std::cout << " ";
  }
  std::cout << std::endl;
}
 
// print a range of simple elements to std::cout
template <typename R> void print_simple_range(R &&rg) { // NOLINT (cppcoreguidelines-missing-std-forward)
  for (auto &&x : rg) { std::cout << x << " "; }
  std::cout << std::endl;
}