Path: csiph.com!xmission!news.glorb.com!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: Inconsistent arithmetic evaluation of parameters Date: Wed, 2 Sep 2015 10:06:28 -0400 Lines: 36 Approved: bug-bash@gnu.org Message-ID: References: <61895190-83A6-4D62-B90E-65023D5E966B@gmail.com> Reply-To: chet.ramey@case.edu NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Trace: usenet.stanford.edu 1441202797 29317 208.118.235.17 (2 Sep 2015 14:06:37 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu To: Clint Hepner , bug-bash@gnu.org Envelope-to: bug-bash@gnu.org X-Enigmail-Draft-Status: N1110 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 In-Reply-To: <61895190-83A6-4D62-B90E-65023D5E966B@gmail.com> X-Junkmail-Status: score=10/60, host=mpv5.cwru.edu X-Junkmail-Whitelist: YES (by domain whitelist at mpv1.tis.cwru.edu) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 129.22.105.36 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com gnu.bash.bug:11460 On 9/1/15 12:50 AM, Clint Hepner wrote: > Bash Version: 4.3 > Patch Level: 42 > Release Status: release > > Description: > > Parameter names are recursively evaluated in an arithmetic expression, but this > is not done consistently. Parameter names are expanded and treated as expressions where they need to be evaluated as a number, and as identifiers when they are the subject of assignment. This is the usual way to handle context-dependent evaluation. > Repeat-By: > > foo=bar > bar=5 > echo $(( foo )) # produces 5 > echo $(( foo++ )) # produces 5 > echo $foo # produces 6, not bar > echo $bar # produces 5, not 6 Consider this equivalent expression: oldfoo=foo,foo=foo+1,oldfoo Would you claim that the foo on the lhs of the assignment statement should be expanded to `bar'? How would assignments ever be performed if it were? -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, ITS, CWRU chet@case.edu http://cnswww.cns.cwru.edu/~chet/