This is a cool trick I learned from bisqwit’s video.

A typical for loop in C++:

for (auto i = 0UZ; i < N; i++) {

A very cool compile time for-loop in ISO C++20 (or GNU++17 w/gcc 8+):

[&]<std::size_t ...I>(std::index_sequence<I...>)
    (function(I), ...);

Which then effectively gets compiled into:

( function(0),
  /* ... */
  function(N - 1)

The comma operator can be replaced with any other operator in C++, or in the function call as a parameter expansion.

This is useful if function(x) requires a compile time constant, or for unrolling the loop (but the compiler should do that, not you).

Parameter Expansion

[&]<std::size_t ...I>(std::index_sequence<I...>)
    function(std::get<I>(params).get() ...);
(std::make_index_sequence<std::tuple_size_v<decltype(params)>>{ });

The std::get<N>() function requires a template parameter, N, as such it must be some compile-time constant. In this instance, we cannot use a run-time loop, and can opt for this compile-time loop pattern.

Or, we can just:

function(params[0].get(), params[1].get() /* et ad nauseam */);