/tmp/cc7ZiqNQ.o: In function `stress_test(int, int, int)':
main.cpp:(.text+0x1c7): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0x1ed): undefined reference to `Num::operator*=(int)'
/tmp/cc7ZiqNQ.o: In function `main':
main.cpp:(.text+0x8d9): undefined reference to `Num::operator+(Num const&)'
main.cpp:(.text+0xa89): undefined reference to `Num::operator+=(Num const&)'
main.cpp:(.text+0xbcc): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0xc41): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0xdca): undefined reference to `Num::operator+(Num const&)'
main.cpp:(.text+0xe0e): undefined reference to `Num::operator+(Num const&)'
main.cpp:(.text+0xf1c): undefined reference to `Num::operator+(Num const&)'
main.cpp:(.text+0xf5b): undefined reference to `Num::operator+(int)'
main.cpp:(.text+0xf7b): undefined reference to `Num::operator+=(Num const&)'
main.cpp:(.text+0x146d): undefined reference to `Num::operator*(Num const&)'
main.cpp:(.text+0x161d): undefined reference to `Num::operator*=(Num const&)'
main.cpp:(.text+0x1760): undefined reference to `Num::operator*=(int)'
main.cpp:(.text+0x17d5): undefined reference to `Num::operator*=(int)'
main.cpp:(.text+0x195e): undefined reference to `Num::operator*(Num const&)'
main.cpp:(.text+0x19a2): undefined reference to `Num::operator*(Num const&)'
main.cpp:(.text+0x1ab0): undefined reference to `Num::operator*(Num const&)'
main.cpp:(.text+0x1aef): undefined reference to `Num::operator*(int)'
main.cpp:(.text+0x1b0f): undefined reference to `Num::operator*=(Num const&)'
main.cpp:(.text+0x1d0b): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0x1dd5): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0x1e79): undefined reference to `Num::operator*=(int)'
main.cpp:(.text+0x21d5): undefined reference to `Num::operator-(Num const&)'
main.cpp:(.text+0x2380): undefined reference to `Num::operator-=(int)'
main.cpp:(.text+0x2462): undefined reference to `Num::operator+=(int)'
main.cpp:(.text+0x24d7): undefined reference to `Num::operator-=(int)'
main.cpp:(.text+0x265f): undefined reference to `Num::operator-(Num const&)'
main.cpp:(.text+0x26a3): undefined reference to `Num::operator-(Num const&)'
main.cpp:(.text+0x27bf): undefined reference to `Num::operator-(Num const&)'
main.cpp:(.text+0x27fb): undefined reference to `Num::operator-(int)'
main.cpp:(.text+0x2831): undefined reference to `Num::operator+(int)'
main.cpp:(.text+0x284b): undefined reference to `Num::operator-=(Num const&)'
collect2: error: ld returned 1 exit status