In file included from main.cpp:7:0:
num.cpp:3:35: error: default argument given for parameter 2 of 'Num::Num(int, int)' [-fpermissive]
 Num::Num(int value, int modulo = 0) : value(value), modulo(modulo) {
                                   ^
In file included from main.cpp:6:0:
num.h:7:5: note: previous specification in 'Num::Num(int, int)' here
     Num(int value=0, int modulo=0);
     ^~~