Ruby Trivia

Presented at the Berlin Ruby User Group (RUG::B) on October 1, 2015.

Transcript

1. Ruby Trivia
2. In Ruby, a dash may not be used in a variable name… …but before Ruby 2.1, one variable was allowed to be named with a dash. What was it called? Question 1:
3. In Ruby, a dash may not be used in a variable name… …but before Ruby 2.1, one variable was allowed to be named with a dash. What was it called? Hint: It’s a global variable. Question 1:
4. $- Answer 1:
5. Why can’t variable names contain dashes? Bonus Question:
6. Why can’t variable names contain dashes? Bonus Question: Answer: Because the Ruby parser can’t distinguish it from the minus (-) operator between two variables (e.g. forty-two).
7. Ruby may define a special File object in the first file it interprets. What is it called? What does it do? Question 2:
8. Ruby may define a special File object in the first file it interprets. What is it called? Question 2: Hint: When you call read, it reads the file, starting after __END__
9. DATA Answer 2:
10. What happens if you call: DATA.rewind before DATA.read Bonus Question:
11. What happens if you call: DATA.rewind before DATA.read Bonus Question: Answer: It reads the entire file, including the source code.
12. The following line of code is valid Ruby syntax: a = true && return
 But this line of code is not: a = return && true What is the error message? Question 3:
13. void value expression Answer 3:
14. When you convert the range: (1..3).to_a You get the array:
 [1, 2, 3]
 What is the result of: (3..1).to_a Question 4:
15. [] Answer 4:
16. What method would need to be added to the Range interface to make descending sequences possible? Bonus Question:
17. What method would need to be added to the Range interface to make descending sequences possible? Bonus Question: Answer: pred (the opposite of succ).
18. What Ruby class mixes-in Comparable but doesn’t define the spaceship (<=>) operator? Question 5:
19. What Ruby class mixes-in Comparable but doesn’t define the spaceship (<=>) operator? Hint: It’s a descendant of Numeric. Question 5:
20. Complex Answer 5:
21. Thanks for playing! Follow @sferik on Twitter for more Ruby trivia and practica.