calc++ example driver::scan_*

Bison.doc v3.8.1

I found the body for Driver::scan_begin and Driver::scan_end in 
scanner.ll. Shouldn't this be colocated with the Driver class source 
code? I (personally) have never seen the body of a class prototype 
function defined in any other location than the class source. Isn't this 
an example of poor coding?

thanks
art