View Compilation Error

0_0_31487232_8444.cpp: In function 'int main()':
0_0_31487232_8444.cpp:18:22: error: reference to 'function' is ambiguous
         sort(a, a+n, function);
                      ^
0_0_31487232_8444.cpp:5:6: note: candidates are: bool function(int, int)
 bool function(int i, int j)
      ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/x86_64-w64-mingw32/bits/stdc++.h:70:0,
                 from 0_0_31487232_8444.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/functional:1834:11: note:                 template<class _Signature> class std::function
     class function;
           ^