Where did I go wrong?

Question

x = 5
=> 5
a = 2
=> 2
b = x + a
=> 7
a = 29
=> 29
puts b
7
=> nil
puts a
29
=> nil
puts b
7
=> nil

Is b = x + a a snapshot in time that stays that way forever no matter what changes about x or a?

Answer 1

Your variables are getting references to existing objects. Notice how the object_id is the same regardless of how I specify "7" (or change a variable that originally led to the object for 7).

https://code.sololearn.com/cbYnENB5Gh3u/?ref=app

If you want to look more at how object_id works (close to your example):
https://launchschool.com/blog/references-and-mutability-in-ruby

Answer 2

Your followup question...track changes to vars...perhaps by using "watches" (a debugging term):

debugging: trace_var
http://phrogz.net/ProgrammingRuby/trouble.html

Pry...to get at the code state:
http://pryrepl.org

https://stackoverflow.com/questions/41811558/how-can-i-watch-a-variable-in-ruby-pry

Answer 3

b stores the result of the addition x+a. That result is 7.
It is not storing references to 'x' and 'a'.

Answer 4

is there anything like a variable that stores references to x and a and tracks the changes if them?