In designing complex systems, it's 
important to break the big problem down 
into smaller and smaller pieces. 
We've see that idea again and again 
throughout the course. 
But in the next few videos, we're 
going to look at another idea for 
managing the complexity of big systems. 
This idea has to do with reducing the 
amount of repetition in our code. 
It's a concept called abstraction, and 
the way it's going to work, is that we're 
going to take function definitions, cases 
where we have two or more examples of 
very similar functions and pull out from 
them, a more general function, which will 
let us later plug in the details of the 
different functions. 
So we're going to get less code, and more 
of our code will be more general or more 
abstract. 
It's going to be kind of fun, and what's 
going to happen here is that all of this 
discipline you've learned about type 
comments and templates and template 
rules, well all of that's going to pay 
off in a really big way in these videos.