How is the following code giving an o/p of [0,2,4,6,8,10,12,14,16,18]
nums = Array.new(10) { |e| e = e * 2 }
puts "#{nums}"
Asked
Active
Viewed 354 times
0
-
1It doesn't. It outputs `[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]` – user12341234 Apr 02 '16 at 23:25
-
yeah sorry for that. Edited it but still can't understand the reason – Mukul Chakravarty Apr 02 '16 at 23:26
-
1[Have you read the documentation?](http://ruby-doc.org/core/Array.html#method-c-new) Also the `e = ` part is unnecessary. – cremno Apr 02 '16 at 23:27
-
@MukulChakravarty what output did you expect and why? – Stefan Apr 02 '16 at 23:29
-
@stefan it is written e=e*2. so how is the value being generated ? is it like 0*2 then 1*2...? – Mukul Chakravarty Apr 02 '16 at 23:34
-
Well, yes. Although the assignment is superfluous, because `e` is never used afterwards. Your code is equivalent to `Array.new(10) { |index| index * 2 }`. The array is created based on the block's return value(s). – Stefan Apr 02 '16 at 23:38
-
@ so basically in the above code index is iterating from 0..9 and being multiplied by 2 each time. – Mukul Chakravarty Apr 02 '16 at 23:40
-
1Exactly, you could also write `(0..9).map { |e| e * 2 }` to get that result. – Stefan Apr 02 '16 at 23:48
-
Another way: `r = (0..9); (2*r.first..2*r.last).step(2).to_a`. – Cary Swoveland Apr 03 '16 at 01:32
2 Answers
0
I believe the idea here is that e represents each "number" passed as the argument in your {} block, populating it the multiple of 2 in an array, and you end up manipulating it by passing an argument. see more details there http://ruby-doc.org/core-2.2.1/Array.html
>> new_array = Array.new(10)
=> [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil]
>> new_array = Array.new(10) { |e| e * 2 }
=> [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
>> new_array = Array.new(10) { |e| e }
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Diego
- 594
- 2
- 10
- 29
0
The index value is what gets piped into the block. The return value from the block gets placed into the array at that index.
efreezy
- 253
- 1
- 3
- 12