C++ Moscow

template <typename ...T>
constexpr auto first_plus_last(T... values) -> T...[0] {
   return T...[0](values...[0] + values...[sizeof...(values) - 1]);
}
int main() {
   static_assert(first_plus_last(1, 2, 10) == 11);
]

namespace xstl {
   template <typename... Ts>
   struct tuple {
      Ts... elems;
   }
}
xstl::tuple tup{1, 2, 3};

constexpr auto r = ^int
typename[:r:] x = 42;       // Same as: int x = 42;
typename[:^char:] c = '*';  // Same as: char c = '*';

template <template auto> struct takes_anything { };
int main() {
   takes_anything<int> a;
   takes_anything<1> b;
}

// global.hpp
#include <iostream>
template <typename T> void dump(T val) { std::cout << val << std::endl; }

// global.cppm
module;
#include "global.hpp"
export module global;
export template <typename T> void output(T item) { dump(item); }

// main.cpp
import global;
int main() { output(42); }

template <typename... T>
constexpr auto first_plus_last(T... values) -> T...[0] {
    return T...[0](values...[0] + values...[sizeof...(values)-1]);
}

int main() {
    static_assert( first_plus_last(1, 2, 10) == 11 );
}

template<in-matrix InMat, class Triangle, in-vector InVec, out-vector OutVec>
void cholesky_solve(InMat A, Triangle t, InVec b, OutVec x)
{
  using std::linalg::explicit_diagonal, std::linalg::transposed, std::linalg::triangular_matrix_vector_solve;

  if constexpr (std::is_same_v<Triangle, upper_triangle_t>) {
    // Solve Ax=b where A = U^T U. Solve U^T c = b, using x to store c.
    triangular_matrix_vector_solve(transposed(A),
      opposite_triangle(t), explicit_diagonal, b, x);
    // Solve U x = c, overwriting x with result.
    triangular_matrix_vector_solve(A, t, explicit_diagonal, x);
  }
  else {
    // ...
  }
}

// Before:
std::vformat(str, std::make_format_args(42));
// After:
std::format(std::runtime_format(str), 42);

// Здесь мы хотим переключиться в отладчик
std::breakpoint_if_debugging();
// А здесь мы из него возвращаемся