Is there a compact equivalent to Python range() in C++/STL

In C++11, there's std::iota:

#include <vector>
#include <numeric> //std::iota

int main() {
    std::vector<int> x(10);
    std::iota(std::begin(x), std::end(x), 0); //0 is the starting number
}

C++20 introduced a lazy version (just like Python) as part of the ranges library:

#include <iostream>
#include <ranges>

namespace views = std::views;

int main() {
    for (int x : views::iota(0, 10)) {
        std::cout << x << ' '; // 0 1 2 3 4 5 6 7 8 9
    }
}

There is boost::irange:

std::vector<int> x;
boost::push_back(x, boost::irange(0, 10));

I ended up writing some utility functions to do this. You can use them as follows:

auto x = range(10); // [0, ..., 9]
auto y = range(2, 20); // [2, ..., 19]
auto z = range(10, 2, -2); // [10, 8, 6, 4]

The code:

#include <vector>
#include <stdexcept>

template <typename IntType>
std::vector<IntType> range(IntType start, IntType stop, IntType step)
{
  if (step == IntType(0))
  {
    throw std::invalid_argument("step for range must be non-zero");
  }

  std::vector<IntType> result;
  IntType i = start;
  while ((step > 0) ? (i < stop) : (i > stop))
  {
    result.push_back(i);
    i += step;
  }

  return result;
}

template <typename IntType>
std::vector<IntType> range(IntType start, IntType stop)
{
  return range(start, stop, IntType(1));
}

template <typename IntType>
std::vector<IntType> range(IntType stop)
{
  return range(IntType(0), stop, IntType(1));
}

Tags:

Python

C++