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  1. #include <iostream>
  2.  
  3. template < size_t N, typename T >
  4. struct param_packer : param_packer<N-1,T>
  5. {
  6.     int value;
  7.  
  8.     param_packer( param_packer<N-1,T> const & other, 
  9.                   int last )
  10.     : param_packer<N-1,T>(other), value(last) 
  11.     { }
  12.  
  13.     param_packer<N+1,T>
  14.     operator,( T append ) const {
  15.         return param_packer<N+1,T>( *this, append );
  16.     }
  17. };
  18.  
  19. template < typename T >
  20. struct param_packer<0,T>
  21. {
  22.     param_packer<1,T>
  23.     operator,( T first ) const {
  24.         return param_packer<1,T>( *this, first );
  25.     }
  26. };
  27.  
  28. template < size_t I, size_t N, typename T >
  29. T&
  30. param_at( param_packer<N,T> & pack ) {
  31.     return static_cast< param_packer<I+1,T>* >(&pack)->value;
  32. }
  33.  
  34. param_packer<0,int> _;
  35.  
  36. template < size_t N >
  37. void foo( param_packer<N, int> pack ) {
  38.     std::cout << "N = " << N << std::endl;
  39.     std::cout << "\t param at <0> is: " << param_at<0>( pack ) << std::endl;
  40.     std::cout << "\t param at <N-1> is: " << param_at<N-1>( pack ) << std::endl;
  41. }
  42.  
  43. int main() {
  44.  
  45.     foo( (_, 1, 2) );
  46.  
  47. }
Success #stdin #stdout 0s 2852KB
comments (?)
stdin 
Standard input is empty
stdout 
N = 2
	 param at <0> is: 1
	 param at <N-1> is: 2
https://ideone.com/Qpj9EM
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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