The promise of multiple dispatch is that it allows every library to be generic. One author writes a library that calculates $COMPLICATEDTHING; another author wr

The promise of multiple dispatch is that it allows every library to be generic. One author writes a library that calculates $COMPLICATEDTHING; another author writes a library that implements a new type of number, such as ranges; provided the second library defines all the methods that the first uses, then, magically, they work together and you can calculate $COMPLICATEDTHING on ranges! That is the thing that Julia does that nothing else does.