/in/foo.cc: In function 'bool e(double, double)':
/in/foo.cc:80:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status