In file included from /in/ex3.cpp:4:0:
/in/cipher.h:20:16: error: variable or field 'decrypt_c' declared void
 void decrypt_c(string line);
                ^~~~~~
/in/cipher.h:20:16: error: 'string' was not declared in this scope
/in/cipher.h:20:16: note: suggested alternatives:
In file included from /usr/include/c++/7/iosfwd:39:0,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/ex3.cpp:1:
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
   typedef basic_string<char>    string;
                                 ^~~~~~
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
In file included from /in/ex3.cpp:4:0:
/in/cipher.h:22:16: error: variable or field 'decrypt_s' declared void
 void decrypt_s(string line);
                ^~~~~~
/in/cipher.h:22:16: error: 'string' was not declared in this scope
/in/cipher.h:22:16: note: suggested alternatives:
In file included from /usr/include/c++/7/iosfwd:39:0,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/ex3.cpp:1:
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
   typedef basic_string<char>    string;
                                 ^~~~~~
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
In file included from /in/ex3.cpp:4:0:
/in/cipher.h:24:16: error: variable or field 'encrypt_c' declared void
 void encrypt_c(string line);
                ^~~~~~
/in/cipher.h:24:16: error: 'string' was not declared in this scope
/in/cipher.h:24:16: note: suggested alternatives:
In file included from /usr/include/c++/7/iosfwd:39:0,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/ex3.cpp:1:
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
   typedef basic_string<char>    string;
                                 ^~~~~~
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
In file included from /in/ex3.cpp:4:0:
/in/cipher.h:26:16: error: variable or field 'encrypt_s' declared void
 void encrypt_s(string line);
                ^~~~~~
/in/cipher.h:26:16: error: 'string' was not declared in this scope
/in/cipher.h:26:16: note: suggested alternatives:
In file included from /usr/include/c++/7/iosfwd:39:0,
                 from /usr/include/c++/7/ios:38,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from /in/ex3.cpp:1:
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
   typedef basic_string<char>    string;
                                 ^~~~~~
/usr/include/c++/7/bits/stringfwd.h:74:33: note:   'std::__cxx11::string'
/in/ex3.cpp: In function 'int main(int, char**)':
/in/ex3.cpp:37:13: error: 'encrypt_c' was not declared in this scope
             encrypt_c();
             ^~~~~~~~~
/in/ex3.cpp:41:13: error: 'decrypt_c' was not declared in this scope
             decrypt_c();
             ^~~~~~~~~
/in/ex3.cpp:52:13: error: 'encrypt_s' was not declared in this scope
             encrypt_s();
             ^~~~~~~~~
/in/ex3.cpp:56:13: error: 'decrypt_s' was not declared in this scope
             decrypt_s();
             ^~~~~~~~~
/in/compile/Makefile:20: recipe for target 'ex3.o' failed
make: *** [ex3.o] Error 1