# A bug in ranges? **URL:** \ **Category:** Ruby\ **Created:** [May 28, 2006, 2:29pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321 "2006-05-28T14:29:50Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 28, 2006, 2:29pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/1 "2006-05-28T14:29:50Z")
I think I may have stumbled upon a minor bug in ranges. on my system, (“Z”…“AA”).map returns [] while “Z”.succ returns “AA” “Z”.upto(“AA”) also returns [] ruby 1.8.4 (2005-12-24) [i686-darwin8.6.1] Is this a real bug, or am I expecting behavior that really shouldn’t be there? \_Kevin ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 28, 2006, 4:27pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/2 "2006-05-28T16:27:20Z")
On 5/28/06, Kevin O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I think I may have stumbled upon a minor bug in ranges. > (“Z”…“AA”).map returns [] > while > “Z”.succ returns “AA” > “Z”.upto(“AA”) also returns [] > Is this a real bug, or am I expecting behavior that really shouldn’t be > there? Character ranges act funny, is all. You’re expecting odd behaviour, really. -austin ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 28, 2006, 7:17pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/3 "2006-05-28T19:17:00Z")
On 5/28/06, Kevin O. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ## “Z”.succ returns “AA” > > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). By looking at the definition of the Range class [http://www.ruby-doc.org/core/classes/Range.html](http://www.ruby-doc.org/core/classes/Range.html) - please note that x…y is the same as Range.new(x,y) - one can conclude that Ranges are constructed using \<=\> and .succ. While it is true that “Z”.succ == “AA” it is also true that “Z” \<=\> “AA” is implying “Z”\>“AA” and therefore Range(“Z”…“AA”) seems correctly empty. What might come as a surprise is that you have found a ruby object that is greater than its successor but that depends on the kind of _order_ we are dealing with. This oddness comes from String, not from Range though. By carefully looking at the definition of succ and \<=\> in String one can ask oneself if constructing Ranges from Strings is very useful in all contexts because \<=\> and succ do not seem to be desinged for the same view of the String domain. BTW what do you think (“AA”…“Z”).to\_a delivers (should be infinite by the same reasoning, should it not?). It seems therefore that some classes are not made to be used for Ranges although they are Compareable and Enumerable which is not very reassuring. I guess you just opened Pandorra’s can ☹ Maybe that is because it was not clear that “\<=\>” and “succ” depend on each other by the design of the language and as they are used for other things “\<=\>” for Compareable one could argue that we have too closely coupled bahvior here. And while one could argue so, I do! Different methods should be used to define Range (e.g. range\_smaller?, range\_next). Cheers Robert – Deux choses sont infinies : l’univers et la bêtise humaine ; en ce qui concerne l’univers, je n’en ai pas acquis la certitude absolue. - Albert Einstein ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 29, 2006, 3:55am UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/4 "2006-05-29T03:55:02Z")
Robert D. wrote: > Just another point which is troubling: > > irb(main):025:0\> (“Z”…“AA”) === “Z” > =\> false > irb(main):026:0\> (“AA”…“Z”) === “Z” > =\> true > > and > > irb(main):030:0\* (“AA”…“Z”) === “Z” > =\> true > irb(main):031:0\> (“AA”…“Z”) === “AA” > =\> true > irb(main):035:0\> (“AA”…“Z”) === “AB” > =\> trueirb(main):036:0\> (“AA”…“Z”) === “A”\*1764 > =\> true I put together a short class to do LetterSeries. It implements \<=\> and succ in a way that lets it act correctly in a range object. [http://www.sciwerks.com/blog/2006/05/28/ruby-series-az/](http://www.sciwerks.com/blog/2006/05/28/ruby-series-az/) ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 28, 2006, 9:18pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/5 "2006-05-28T21:18:16Z")
Just another point which is troubling: irb(main):025:0\> (“Z”…“AA”) === “Z” =\> false irb(main):026:0\> (“AA”…“Z”) === “Z” =\> true and irb(main):030:0\* (“AA”…“Z”) === “Z” =\> true irb(main):031:0\> (“AA”…“Z”) === “AA” =\> true irb(main):035:0\> (“AA”…“Z”) === “AB” =\> trueirb(main):036:0\> (“AA”…“Z”) === “A”\*1764 =\> true ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 29, 2006, 3:42pm UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/6 "2006-05-29T15:42:45Z")
On 5/29/06, Ryan L. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Sorry if my confused post did not help to pass my point, thx also for the > pointer. > It seems to me, and that is eventually a clear statement from my side > ;), > that this needs more discussion. > Please kindly try to forget what I have written sofar - because of the > noise - and evaluate the following statement. It is bad that Range builds its behavior upon \<=\> and succ, because \<=\> and succ are not designed (not always at least) to work together for that purpose. I conclude from Matz’ post that this confusion could be clarified by redesigning Range to be build on a contract that does not interfere with other contracts. Changing the paradigme. I am well aware that such a redesign might have more impacts ( for logical compatibility with the Enumerable mixin f.i.) than one might think of at first sight but the OP’s confusion and the previous discussion make it quite clear to me… Thanks for listinening. Robert – Deux choses sont infinies : l’univers et la bêtise humaine ; en ce qui concerne l’univers, je n’en ai pas acquis la certitude absolue. - Albert Einstein ---
**Author:** ![olbrich](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/5f9b8f/32.png) [@olbrich](https://www.ruby-forum.com/u/olbrich)\ **Post date:** [May 29, 2006, 4:04am UTC](https://www.ruby-forum.com/t/a-bug-in-ranges/95321/7 "2006-05-29T04:04:43Z")
Just an FYI, this general topic of ranges and strings has been discussed extensively in the recent past: [http://groups.google.com/group/comp.lang.ruby/browse\_thread/thread/cfc720a7a0313323/9d17db883a1d6100](http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/cfc720a7a0313323/9d17db883a1d6100) [http://groups.google.com/group/comp.lang.ruby/browse\_thread/thread/2d6a59a136abce3d/ccf66936477e73a7](http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/2d6a59a136abce3d/ccf66936477e73a7) Ryan