/in/foo.cc: In function 'int main()':
/in/foo.cc:26:5: error: reference to 'hash' is ambiguous
a=hash(a); b=hash(b);
^~~~
/in/foo.cc:10:5: note: candidates are: int hash(int)
int hash(int x){
^~~~
In file included from /usr/include/c++/6/bits/basic_string.h:5643:0,
from /usr/include/c++/6/string:52,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/istream:38,
from /usr/include/c++/6/sstream:38,
from /usr/include/c++/6/complex:45,
from /usr/include/c++/6/ccomplex:39,
from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
from /in/foo.cc:1:
/usr/include/c++/6/bits/functional_hash.h:58:12: note: template<class _Tp> struct std::hash
struct hash;
^~~~
/in/foo.cc:26:16: error: reference to 'hash' is ambiguous
a=hash(a); b=hash(b);
^~~~
/in/foo.cc:10:5: note: candidates are: int hash(int)
int hash(int x){
^~~~
In file included from /usr/include/c++/6/bits/basic_string.h:5643:0,
from /usr/include/c++/6/string:52,
from /usr/include/c++/6/bits/locale_classes.h:40,
from /usr/include/c++/6/bits/ios_base.h:41,
from /usr/include/c++/6/ios:42,
from /usr/include/c++/6/istream:38,
from /usr/include/c++/6/sstream:38,
from /usr/include/c++/6/complex:45,
from /usr/include/c++/6/ccomplex:39,
from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:52,
from /in/foo.cc:1:
/usr/include/c++/6/bits/functional_hash.h:58:12: note: template<class _Tp> struct std::hash
struct hash;
^~~~