Path: csiph.com!goblin3!goblin1!goblin.stu.neva.ru!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: Error on arithmetic evaluation of `~0`. Date: Wed, 26 Dec 2018 12:10:24 -0500 Organization: ITS, Case Western Reserve University Lines: 44 Approved: bug-bash@gnu.org Message-ID: References: <25e8adf0-96d5-1e38-faea-e7620ba3f846@case.edu> 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: 8bit X-Trace: usenet.stanford.edu 1545844237 13337 208.118.235.17 (26 Dec 2018 17:10:37 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu, bug-bash To: Bize Ma Envelope-to: bug-bash@gnu.org X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:cc:subject:to:references:from:openpgp :autocrypt:organization:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=naT8NsDEhGcRWuGcCn9wgcEXHIGBWTqlLEVtcc+EwCI=; b=OH9kwKJYUppjIB9bExpBS36SfaEoDCx7OiKPAYDRPfgpEqHFxY/oc/LbOcQocb8Ue7 UlfRASqF6E3qoy5fJJbiHkHx73j5eBRpvo4Z+NMdSQuBp8IJ58r6/s6ySfDJCOrWb1MR PB1vpvKpy+eRzz7s+tR3SBij5ckPvo0pAUb/S/LxNr1h+t/9rYFDzywymGdgqIUxLXEZ h5JPF5AV4ECvVmzZcw5ClNQEcqVyNuBuGatigZJCSRiIuZgDSbPoW/W0TPrm3jLt2itn zfhxaQOd1EGRURN9xgTXtvzgVraljvMpYt6Iv0RAvJ3UR2TIHIrEzUkG4h9JEmncJWGP kIvQ== X-Gm-Message-State: AA+aEWYy0A2vBVrtoe678A3tLeaqiVFAt5fb+bl8gXnVLyAyPGlmNdRQ LxyyWJJ/p9P9H8O2BVQaMB7iYCKD2uOnHZZPDORXXmMrgdJMrCDN2ms6MP8RUzMQ0G2q/24oaP/ egILv7TrriF0= X-Received: by 2002:a5b:310:: with SMTP id j16-v6mr20888371ybp.320.1545844227553; Wed, 26 Dec 2018 09:10:27 -0800 (PST) X-Google-Smtp-Source: AFSGD/XJKyPjvUBReB42udyHNAzys5Jr99ey7+L2v+tG5Gpq0Aiw5fmgdhsMR0lqtHw7bPt0Nq3//w== X-Received: by 2002:a5b:310:: with SMTP id j16-v6mr20888328ybp.320.1545844227117; Wed, 26 Dec 2018 09:10:27 -0800 (PST) Openpgp: preference=signencrypt Autocrypt: addr=chet.ramey@case.edu; prefer-encrypt=mutual; keydata= xsDiBEEOsGwRBACFa0A1oa71HSZLWxAx0svXzhOZNQZOzqHmSuGOG92jIpQpr8DpvgRh40Yp AwdcXb8QG1J5yGAKeevNE1zCFaA725vGSdHUyypHouV0xoWwukYO6qlyyX+2BZU+okBUqoWQ koWxiYaCSfzB2Ln7pmdys1fJhcgBKf3VjWCjd2XJTwCgoFJOwyBFJdugjfwjSoRSwDOIMf0D /iQKqlWhIO1LGpMrGX0il0/x4zj0NAcSwAk7LaPZbN4UPjn5pqGEHBlf1+xDDQCkAoZ/VqES GZragl4VqJfxBr29Ag0UDvNbUbXoxQsARdero1M8GiAIRc50hj7HXFoERwenbNDJL86GPLAQ OTGOCa4W2o29nFfFjQrsrrYHzVtyA/9oyKvTeEMJ7NA3VJdWcmn7gOu0FxEmSNhSoV1T4vP2 1Wf7f5niCCRKQLNyUy0wEApQi4tSysdz+AbgAc0b/bHYVzIf2uO2lIEZQNNt+3g2bmXgloWm W5fsm/di50Gm1l1Na63d3RZ00SeFQos6WEwLUHEB0yp6KXluXLLIZitEJM0aQ2hldCBSYW1l eSA8Y2hldEBjd3J1LmVkdT7CYQQTEQIAIQIbAwYLCQgHAwIDFQIDAxYCAQIeAQIXgAUCQ+La kQIZAQAKCRC7WGnwZOp0q9rGAJ4sRGLmlF8klZTH75z7jyQScpU6aACeNMahjWIhumt4u96d 9mdMJqlabVnOwE0EQQ6wbxAEAJCukwDigRDPhAuI+lf+6P64lWanIFOXIndqhvU13cDbQ/Wt 5LwPzm2QTvd7F+fcHOgZ8KOFScbDpjJaRqwIybMTcIN0B2pBLX/C10W1aY+cUrXZgXUGVISE MmpaP9v02auToo7XXVEHC+XLO9IU7/xaU98FL69l6/K4xeNSBRM/AAMHA/wNAmRBpcyK0+Vg gZ5esQaIP/LyolAm2qwcmrd3dZi+g24s7yjV0EUwvRP7xHRDQFgkAo6++QbuecU/J90lxrVn QwucZmfz9zgWDkT/MpfB/CNRSKLFjhYq2yHmHWT6vEjw9Ry/hF6Pc0oh1a62USdfaKAiim0n VxxQmPmiRvtCmcJJBBgRAgAJBQJBDrBvAhsMAAoJELtYafBk6nSr43AAn2ZZFQg8Gs/zUzvX Mt7evaFqVTzcAJ0cHtKpP1i/4H4R9+OsYeQdxxWxTQ== User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 In-Reply-To: Content-Language: en-US X-Junkmail-Status: score=8/90, host=mpv1-2015.case.edu X-Junkmail-PrAS-Raw: score=8/90, refid=2.7.2:2018.12.26.164216:17:8.317, ip=, rules=__YOUTUBE_RCVD, __X_GOOGLE_DKIM_SIGNATURE, __HAS_REPLYTO, __HAS_CC_HDR, __MULTIPLE_RCPTS_CC_X2, __CC_NAME, __CC_NAME_DIFF_FROM_ACC, __SUBJ_REPLY, __PHISH_SPEAR_SUBJ_ALERT, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __TO_MALFORMED_2, __TO_NAME, __TO_NAME_DIFF_FROM_ACC, __REFERENCES, __HAS_FROM, FROM_EDU_TLD, __HAS_MSGID, __SANE_MSGID, DATE_TZ_NA, __USER_AGENT, __MOZILLA_USER_AGENT, __MIME_VERSION, __IN_REP_TO, __CT, __CT_TEXT_PLAIN, __CTE, __REPLYTO_SAMEAS_FROM_ADDY, __REPLYTO_SAMEAS_FROM_ACC, __FROM_DOMAIN_IN_ANY_CC2, __REPLYTO_SAMEAS_FROM_DOMAIN, __ANY_URI, __URI_WITH_PATH, __URI_NO_WWW, __CP_URI_IN_BODY, __FRAUD_MONEY_CURRENCY_DOLLAR, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, __URI_NOT_IMG, __FORWARDED_MSG, __NO_HTML_TAG_RAW, BODY_SIZE_1300_1399, BODYTEXTP_SIZE_3000_LESS, __MIME_TEXT_P1, __MIME_TEXT_ONLY, __URI_NS, HTML_00_01, HTML_00_10, [TRUNCATED], so=2010-03-03 19:42:08, dmn=2016-08-03-0138 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] [fuzzy] X-Received-From: 129.22.103.226 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.21 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:14959 On 12/23/18 12:01 PM, Bize Ma wrote: > Chet Ramey (>) wrote: > > > > > While this works: > > > > var=(hello); echo "${var[ ~0]}" > > hello > > Because negative array subscripts count backwards from the end of the > array. > > > Doh!, yes. And, because of that: "${var[-1]}" > should give the *last* element of array "var", shouldn't it? Yes, if it's an array variable. > Consequently,  this happens: > >     $ unset var; var[0]=77; echo "${var[0]}"; echo "${var[-1]}" >     77 >     77 >   > The only value in var is at index 0, which means it is also the *last* value. Correct. > > The point being that a variable which has an scalar value "var=hello" > should act (for most practical cases) as an array for which only the > value at address 0 has been defined. > > Both command line above should have printed "hello". No. 0 is the only valid subscript for a non-array variable. The difference between bash and other shells that implement this feature is that bash warns about negative subscripts. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/