# My second day of learning Ruby (and my seconds feels) **URL:** \ **Category:** Ruby\ **Created:** [October 19, 2006, 12:38pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851 "2006-10-19T12:38:29Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 12:38pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/1 "2006-10-19T12:38:29Z")
Hi all, Thanks for your anwers yesterday. Are you ready for my next day of learning Ruby? 😉 ## First impressions of ranges: let’s try ranges as sequences: irb(main):271:0\> (0
2).each { |bb| puts bb } 0 1 2 =\> 0
2 irb(main):272:0\> (0
2).each { |bb| puts bb } 0 1 =\> 0
2 very fun. Now let’s try ranges as conditions: irb(main):282:0\* a=[“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] irb(main):283:0\> a.each { |b| puts b if b=~/b/
b=~/d/ } bbbb bbbbbb ccc dddddd =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] irb(main):284:0\> a.each { |b| puts b if b=~/b/
b=~/d/ } bbbb bbbbbb ccc dddddd =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] “Oups it did not it again!” 
 and 
 seems not working on the same way if you use ranges as sequences or ranges as conditions. My point of view: (unless I’m making a mistake) It gets confusing. ## First impressions of blocks: irb(main):293:0\* a=[“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] irb(main):294:0\> a.each { |a| puts a } aaa bbbb bbbbbb ccc dddddd =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] irb(main):295:0\> a =\> “dddddd” a is changed. scope of the block is not duplicate/separate? Florent, ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 1:55pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/2 "2006-10-19T13:55:20Z")
Florent G. a Ă©crit : > dddddd > =\> [“aaa”, “bbbb”, “bbbbbb”, “ccc”, “dddddd”] > irb(main):295:0\> a > =\> “dddddd” > > a is changed. scope of the block is not duplicate/separate? I’ve got my anwser at Chapter 7, Part I of pickaxe Ruby book: Variable Scope, Loops, and Blocks (
cut
) However, if at the time the block executes a local variable already exists with the same name as that of a variable in the block, the existing local variable will be used in the block. Its value will therefore be available after the block finishes. Florent, ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 1:55pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/3 "2006-10-19T13:55:20Z")
On 10/19/06, Florent G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > 
 and 
 seems not working on the same way if you use ranges as > sequences or ranges as conditions. My point of view: (unless I’m making > a mistake) It gets confusing. Personally, I don’t think I ever saw someone use a range as a condition. I don’t even know if they’re supposed to be used that way, since the name “range” pretty much implies “sequence” rather than “condition” to me. What were you trying to do in your example? > First impressions of blocks: > a is changed. scope of the block is not duplicate/separate? IIRC, a block can “see” and use variables in the scope immediately outside it. This is intended, and useful. They work more like the code you put inside a loop than the code you put inside a method call. Would you do the following in another language? for (i = 0; i \<= 10; i++) { i = some\_array[i]; } ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 4:19pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/4 "2006-10-19T16:19:01Z")
On 10/19/06, Bira [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On 10/19/06, Florent G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > 
 and 
 seems not working on the same way if you use ranges as > > sequences or ranges as conditions. My point of view: (unless I’m making > > a mistake) It gets confusing. > > Personally, I don’t think I ever saw someone use a range as a > condition. I don’t even know if they’re supposed to be used that way, > since the name “range” pretty much implies “sequence” rather than > “condition” to me. It’s the allmighty flip-flop operator\*. Useful only for obfuscating code. It’s not worthy of your attention unless your implementing ruby. - [http://redhanded.hobix.com/inspect/hopscotchingArraysWithFlipFlops.html](http://redhanded.hobix.com/inspect/hopscotchingArraysWithFlipFlops.html) ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 6:31pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/5 "2006-10-19T18:31:05Z")
On Thu, Oct 19, 2006 at 07:37:02PM +0900, Florent G. wrote: > dddddd > 
 and 
 seems not working on the same way if you use ranges as > sequences or ranges as conditions. My point of view: (unless I’m making > a mistake) It gets confusing. The difference between 
 and 
 in a conditional is a little different than when used in a range. This is described in the PickAxe book on p 327 Second Edition PDF 2007-09-20. The difference is that the two-dot form evaluates the second condition when it enters the true state and the three-dot form does not. So, for example, on a given iteration if the first conditional caused the ``state machine’’ to go into the set state and the second conditional evaluated to true, the two-dot form would return true but switch the state back to unset and the three-dot form would not. Here is the example code from the PickAxe book (spruced up a bit): #! /usr/bin/ruby -w # test behavior of range operator in conditional require ‘pp’ a = (11
20).collect {|i| (i % 4 == 0)
(i % 3 == 0) ? i : nil} pp(a) b = (11
20).collect {|i| (i % 4 == 0)
(i % 3 == 0) ? i : nil} pp(b) Which outputs: [nil, 12, nil, nil, nil, 16, 17, 18, nil, 20] [nil, 12, 13, 14, 15, 16, 17, 18, nil, 20] The two-dot form evaluates both conditionals when i is 12, it returns true but since the second condition evaulates to true the state machine is changed back to unset and subsequent values do not get printed until the first contitional returns true again. Note that even when the second conditional returns true and the state machine is switched to unset, the expression returns true. This is true for both forms. ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 2:27pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/6 "2006-10-19T14:27:40Z")
Bira a Ă©crit : > Personally, I don’t think I ever saw someone use a range as a > condition. I don’t even know if they’re supposed to be used that way, > since the name “range” pretty much implies “sequence” rather than > “condition” to me. What were you trying to do in your example? In the Ruby’s pickaxe book Chapter 5: Ranges - Ranges as sequences - Ranges as conditions - Ranges as intervals ---
**Author:** ![florent\_g](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/977dab/32.png) [@florent\_g](https://www.ruby-forum.com/u/florent_g)\ **Post date:** [October 19, 2006, 10:51pm UTC](https://www.ruby-forum.com/t/my-second-day-of-learning-ruby-and-my-seconds-feels/72851/7 "2006-10-19T22:51:38Z")
Simen E. wrote: > It’s the allmighty flip-flop operator\*. Useful only for obfuscating > code. It’s not worthy of your attention unless your implementing ruby. IIRC, it’s being dropped in Ruby 2.0 anyway.