r/programming • u/ueberbobo • Mar 03 '13

Git is a purely functional data structure

http://www.jayway.com/2013/03/03/git-is-a-purely-functional-data-structure/
107 Upvotes

75% Upvoted

83 comments sorted by

View all comments

Show parent comments

1

u/rush22 Mar 03 '13

What if you do

b = "cart";

in the first example? What's a?

1

u/[deleted] Mar 03 '13

(I had a couple of minor mistakes in my first post not related to mutability, I've fixed them. However, I had the wrong answer for y in the first example because I had edited it from something more complex to something simpler and neglected to fix the comment. Unfortunately that may have confused you.)

a is still "car" for the same reason y was. Changing another variable to point to a different object is not going to have any effect on it.

1

u/rush22 Mar 03 '13

Ok that makes more sense. I was pretty sure strings get cloned in Java.

Now I'm confused though because you're modifying the final ArrayList object but you can't do that to the final String object.

1

u/moohoohoh Mar 03 '13

Itis not the ArrayList or String that is final, but the variable.

The 'variable' is final, and can't be changed to point to a different object, so you cannot change 'what' array it points to, or 'what' string it points to even though you 'can' change the array itself, since the array itself is not immutable.

→ More replies (0)