Ruby Quiz

at 学生エンジニア限定LT大会

Transcript

1. Ruby Quiz Oct. 8, 2017 第4回 学生エンジニア限定LT大会
2. I have only 5 minutes, so I'll speak very fast.
3. Self introduction • Pocke • Actcat, Inc. / SideCI • RuboCop' s core developer • Student at The Open University of Japan
4. SideCI
5. Automated Code Review as a Service
6. Please access here! https://sideci.com
7. Ruby Quiz
8. Question
9. Do you write Ruby?
10. Ruby Quiz • You are a Ruby interpreter. ◦ You are a parse.y. ◦ You are a YARV. • You execute ruby code, and you output result.
11. Quiz 1
12. Q. What does the code output? p(??) p(%_?_)
13. Answer p(??) # => "?" p(%_?_) # => "?"
14. Why?
15. A. Why does it output "?"? p(??) p(%_?_) %<any character>…<any character> is a string literal. e.g.) %_?_ == "?" , %!???! == "???" ?_ is a character literal. e.g.) ?_ == "_" , ?? == "?"
16. Quiz 2
17. Q. What does the code output? p(????::?:) p(% %s% %%%%)
18. Answer p(????::?:) # => ":" p(% %s% %%%%) # => "%"
19. Why????
20. Answer p(????::?:) p(% %s% %%%%) 1. ?? is "?" 2. ? is a part of conditional op 3. ?: is ":" 4. : is a part of conditional op 5. ?: is ":" "?" ? ":" : ":" 1. % %s% is "%s%" 2. % is a format op(Like sprintf) 3. %%% is "" sprintf("%s%", "")
21. Quiz 3
22. Q. What does the code output? a = ["1","2","3"] a&.map(&:to_i)&.&([1])
23. Answer a = ["1","2","3"] a&.map(&:to_i)&.&([1]) # => [1]
24. Why?????
25. Answer a = ["1","2","3"] a&.map(&:to_i)&.&([1]) # => [1] &. is a safe navigation op(nil guard). &:to_i is an implicit to_proc op. A safe navigation op & is an intersection op call (like [1,2,3] & [1])
26. Conclusion
27. • We can write tricky code in Ruby. ◦ Very fun!!! Thank you for listening! Conclusion