View Compilation Error

0_0_36348076_20344.cpp:27:48: error: 'operator()' function uses 'auto' type specifier without trailing return type
   template<class ...U> auto operator()(U &&...a) { 
                                                ^
0_0_36348076_20344.cpp:27:48: note: deduced return type only available with -std=c++1y or -std=gnu++1y
0_0_36348076_20344.cpp:31:32: error: 'YF' function uses 'auto' type specifier without trailing return type
 template<class F> auto YF(F &&f) { 
                                ^
0_0_36348076_20344.cpp:31:32: note: deduced return type only available with -std=c++1y or -std=gnu++1y
0_0_36348076_20344.cpp: In function 'auto YF(F&&)':
0_0_36348076_20344.cpp:32:22: error: 'decay_t' was not declared in this scope
   return YCombinator<decay_t<F>>(forward<F>(f)); 
                      ^
0_0_36348076_20344.cpp:32:30: error: template argument 1 is invalid
   return YCombinator<decay_t<F>>(forward<F>(f)); 
                              ^