From: Run Paint Run Run Date: 2009-07-09T11:30:58+09:00 Subject: [ruby-core:24225] [Bug #1750] Inconsistent Behavior on 1.8 and 1.9 of String#[]= with Single Fixnum Argument Bug #1750: Inconsistent Behavior on 1.8 and 1.9 of String#[]= with Single Fixnum Argument http://redmine.ruby-lang.org/issues/show/1750 Author: Run Paint Run Run Status: Open, Priority: Normal Category: core ruby -v: ruby 1.9.2dev (2009-07-08 trunk 23995) [i686-linux] Brian Ford posted the following to [ruby-core:23706], but it seems to have been passed over, so I'm submitting it as a ticket. Hopefully we can clarify this behaviour, then get the affected RubySpec tests fixed. :-) #### String[]= behaves differently on 1.8 and 1.9 when given a single Fixnum argument == to the size of the string. Given the following code: $ cat string.rb s = "" p s[0] s[0,0] = "a" p s s = "" s[0] = "a" p s s = "x" s[1] = "a" p s these are the results: $ ruby -vw string.rb ruby 1.8.6 (2008-08-11 patchlevel 287) [universal-darwin9.0] nil "a" string.rb:8:in `[]=': index 0 out of string (IndexError) from string.rb:8 $ ruby1.8 -vw string.rb ruby 1.8.8dev (2009-06-04 revision 23638) [i386-darwin9.7.0] nil "a" string.rb:8:in `[]=': index 0 out of string (IndexError) from string.rb:8 $ ruby1.9 -vw string.rb ruby 1.9.2dev (2009-05-28 trunk 23601) [i386-darwin9.7.0] nil "a" "a" "xa" Given any string s of N characters, s[N] == nil, so I understand that to mean that N is out of the bounds of the string. The RDoc for String#[]= states that "The forms that take a +Fixnum+ will raise an +IndexError+ if the value is out of range; the +Range+ form will raise a +RangeError+, and the +Regexp+ and +String+ forms will silently ignore the assignment." The RDoc does not appear to have changed on 1.9. So, my questions are: 1. should ""[0] = "a" work on 1.8 the way it does on 1.9? OR 2. should ""[0] = "a" raise an IndexError on 1.9? If the answer to the above is "it should raise an IndexError on 1.9", then should ""[0,N] = "a" also raise an IndexError? If the answer is ""[0] = "a" should work as it does on 1.9, can we please update the RDoc to somehow explain that while s[N] is out of bounds of the string, you can "replace" that non-existent character with an arbitrary length string. Cheers, Brian ---------------------------------------- http://redmine.ruby-lang.org