From 449777950889588554 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,6d5520f8ce526ad5,start X-Google-Attributes: gidf78e5,public From: Jim Cobban Subject: Pointer to member function restriction in standard Date: 2000/01/24 Message-ID: <388CC286.B7848872@hotmail.com>#1/1 X-Deja-AN: 577116269 X-NNTP-Posting-Host: 206.191.1.177 Approved: stephen.clamage@sun.com (comp.std.c++) X-Accept-Language: en X-UID: 0000000001 X-Status: $$$T Content-Type: multipart/mixed; boundary="------------2A153B3BFFFFB9C79A044A80" Organization: Magma Communications Ltd. Mime-Version: 1.0 NNTP-Posting-Date: Mon, 24 Jan 2000 16:19:55 EDT Newsgroups: comp.std.c++ Originator: clamage@taumet This is a multi-part message in MIME format. --------------2A153B3BFFFFB9C79A044A80 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Could someone please explain to me the rationale behind the restriction documented in paragraph 3 of section 5.3.1 of the standard: "A pointer to member is only formed when an explicit & is used and its operand is a qualified-id not enclosed in parentheses. [Note: that is, the expression &(qualified-id), where the qualified-id is enclosed in parentheses, does not form an expression of type Neither does qualified-id, because there is no implicit conversion from a qualified-id for a nonstatic member function to the type as there is from an lvalue of function type to the type (4.3). Nor is &unqualified-id a pointer to member, even within the scope of the unqualified-id's class. ]" The result of this restriction is what seems unnecessarily ugly code in my program. I am writing a state based parser. So at the end of processing each token I want to set the state for handling the next token. At first I did this with an enumeration, but that then required a switch statement to select the function to be called for each state, so I decided to use a pointer-to-member-function. But that requires the ugly syntax: pmf = &ClassName::StateFunc; where, as the standard says this qualification would not be required if I were not writing this code using classes. I therefore feel that the standard is, in this situation, penalizing me for wanting to program using object oriented techniques. Note that the enforcement of this restriction varies by compiler. I have tried it on Borland, which issues an error message, and on Metrowerks, which accepts the short-hand pmf = StateFunc; -- Jim Cobban jcobban@magma.ca 34 Palomino Dr. Kanata, ON, CANADA K2M 1M1 +1-613-592-9438 --------------2A153B3BFFFFB9C79A044A80 Content-Type: text/x-vcard; charset=us-ascii; name="thesnaguy.vcf" Content-Transfer-Encoding: 7bit Content-Description: Card for Jim Cobban Content-Disposition: attachment; filename="thesnaguy.vcf" begin:vcard n:Cobban;James tel;fax:+1-613-592-9438 tel;home:+1-613-592-9438 x-mozilla-html:FALSE url:http://www.magma.ca/~jcobban version:2.1 email;internet:thesnaguy@hotmail.com title:Consultant adr;quoted-printable:;;34 Palomino Dr.=0D=0A;Kanata;ON;K2M 1M1;Canada fn:Jim Cobban end:vcard --------------2A153B3BFFFFB9C79A044A80-- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]