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#include <iostream>
#include <functional>
 
using namespace std;
 
typedef int value;
 
template<class Signature>
function<void(int, value[])>
thunk( function<Signature> f );
 
 
template<class R, class Arg1>
function<void(int, value[])>
thunk( function<R(Arg1)> f )
{
	return [f](int, value v[]) -> R
	{
		return f(v[0]);
	};
}
 
 
template<class R, class Arg1, class Arg2>
function<void(int, value[])>
thunk( function<R(Arg1, Arg2)> f )
{
	return [f](int, value v[]) -> R
	{
		return f(v[0], v[1]);
	};
}
 
template<class R, class Arg1, class Arg2>
function<void(int, value[])>
thunk( R(*f)(Arg1, Arg2) )
{
	return [f](int, value v[]) -> R
	{
		return f(v[0], v[1]);
	};
}
 
 
void f1(int p1) { cout << "f1\t" << p1 << "\n"; }
void f2(int p1, int p2) { cout << "f2\t" << p1 << "\t" << p2 << "\n"; }
 
int main() {
	int a1[] = {1};
	int a2[] = {3, 4};
 
	// case 1
	auto ufunc = thunk( f2 );
	ufunc(2,a2);
 
 
	// case 2
	auto ff2 = [](int p1, int p2) { cout << "ff2\t" << p1 << "\t" << p2 << "\n"; };
 
	auto ufunc2 = thunk( ff2 );
	ufunc2(2,a2);
 
	return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:60:27: error: no matching function for call to ‘thunk(main()::__lambda3&)’
  auto ufunc2 = thunk( ff2 );
                           ^
prog.cpp:60:27: note: candidates are:
prog.cpp:10:1: note: template<class Signature> std::function<void(int, int*)> thunk(std::function<Signature>)
 thunk( function<Signature> f );
 ^
prog.cpp:10:1: note:   template argument deduction/substitution failed:
prog.cpp:60:27: note:   ‘main()::__lambda3’ is not derived from ‘std::function<Signature>’
  auto ufunc2 = thunk( ff2 );
                           ^
prog.cpp:15:1: note: template<class R, class Arg1> std::function<void(int, int*)> thunk(std::function<R(Arg1)>)
 thunk( function<R(Arg1)> f )
 ^
prog.cpp:15:1: note:   template argument deduction/substitution failed:
prog.cpp:60:27: note:   ‘main()::__lambda3’ is not derived from ‘std::function<R(Arg1)>’
  auto ufunc2 = thunk( ff2 );
                           ^
prog.cpp:26:1: note: template<class R, class Arg1, class Arg2> std::function<void(int, int*)> thunk(std::function<R(Arg1, Arg2)>)
 thunk( function<R(Arg1, Arg2)> f )
 ^
prog.cpp:26:1: note:   template argument deduction/substitution failed:
prog.cpp:60:27: note:   ‘main()::__lambda3’ is not derived from ‘std::function<R(Arg1, Arg2)>’
  auto ufunc2 = thunk( ff2 );
                           ^
prog.cpp:36:1: note: template<class R, class Arg1, class Arg2> std::function<void(int, int*)> thunk(R (*)(Arg1, Arg2))
 thunk( R(*f)(Arg1, Arg2) )
 ^
prog.cpp:36:1: note:   template argument deduction/substitution failed:
prog.cpp:60:27: note:   mismatched types ‘R (*)(Arg1, Arg2)’ and ‘main()::__lambda3’
  auto ufunc2 = thunk( ff2 );
                           ^
prog.cpp:49:6: warning: unused variable ‘a1’ [-Wunused-variable]
  int a1[] = {1};
      ^

Standard output is empty