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