/in/foo.cc:24:1: error: reference to 'complex' is ambiguous
 complex operator + (complex a,complex b){
 ^~~~~~~
/in/foo.cc:18:9: note: candidates are: struct complex
 struct  complex{
         ^~~~~~~
In file included from /usr/include/c++/6/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/complex:63:32: note:                 template<class _Tp> struct std::complex
   template<typename _Tp> class complex;
                                ^~~~~~~
/in/foo.cc:27:1: error: reference to 'complex' is ambiguous
 complex operator - (complex a,complex b){
 ^~~~~~~
/in/foo.cc:18:9: note: candidates are: struct complex
 struct  complex{
         ^~~~~~~
In file included from /usr/include/c++/6/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/complex:63:32: note:                 template<class _Tp> struct std::complex
   template<typename _Tp> class complex;
                                ^~~~~~~
/in/foo.cc:30:1: error: reference to 'complex' is ambiguous
 complex operator * (complex a,complex b){
 ^~~~~~~
/in/foo.cc:18:9: note: candidates are: struct complex
 struct  complex{
         ^~~~~~~
In file included from /usr/include/c++/6/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/complex:63:32: note:                 template<class _Tp> struct std::complex
   template<typename _Tp> class complex;
                                ^~~~~~~
/in/foo.cc:34:17: error: variable or field 'fft' declared void
 inline void fft(complex *X,int type){
                 ^~~~~~~
/in/foo.cc:34:17: error: reference to 'complex' is ambiguous
/in/foo.cc:18:9: note: candidates are: struct complex
 struct  complex{
         ^~~~~~~
In file included from /usr/include/c++/6/ccomplex:39:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
                 from /in/foo.cc:1:
/usr/include/c++/6/complex:63:32: note:                 template<class _Tp> struct std::complex
   template<typename _Tp> class complex;
                                ^~~~~~~
/in/foo.cc:34:26: error: 'X' was not declared in this scope
 inline void fft(complex *X,int type){
                          ^
/in/foo.cc:34:28: error: expected primary-expression before 'int'
 inline void fft(complex *X,int type){
                            ^~~