Lecture 12, Tue 09/04

File permissions, Stacks, Local vs. Global

Code from class

https://github.com/ucsb-cs8-m18/code-from-class/tree/master/09-04

Final next week!

You don’t have to print out ic01 tomorrow.

iClicker Questions

0. What is the octal number that represents the permissions r-x-w---x?

   (a) 614
   (b) 521
   (c) 246
   (d) 241

In-Class Questions / Schedule of Events

• Text prediction program (only preserve alphanumeric things)
• file permissions, octal (see https://ucsb-cs8.github.io/topics/number_conversions/)
  • chmod changes permissions
• reuse, modularity, encapsulation
  • reuse: if I want to do the same thing multiple times, I can put that thing in a function! Then I can just call the function a bunch of times instead of copying and pasting the same code a bunch of times.
    • What from lab05 is an example of reuse and why?
  • modularity: breaking down things into smaller, simpler pieces.
    • Your tree drawing function draws triangles!
  • encapsulation: the user of your function doesn’t need to know how it’s implemented–they just need to know how to call it
    • What from lab05 is an example of encapsulation and why?
• push and pop in the context of lists (push is append)
• RPN calculator example
• local vs. global
  • variables defined inside a function are called local variables. They don’t affect any variables defined with the same name elsewhere. This is good for encapsulation.
  • different functions have different spaces for variables. These are called namespaces.
  • a new namespace is made for every function call (example on p. 208)
  • global variables are those defined outside of any function
    • they can be accessed anywhere, but you need to use special code to update them inside of functions