From owner-sc22wg5 Wed Sep 4 22:06:17 2002 Received: from math.jpl.nasa.gov (math.jpl.nasa.gov [137.79.7.57]) by dkuug.dk (8.9.2/8.9.2) with ESMTP id WAA86126 for ; Wed, 4 Sep 2002 22:06:16 +0200 (CEST) (envelope-from vsnyder@math.jpl.nasa.gov) Received: from math.jpl.nasa.gov (vsnyder@localhost) by math.jpl.nasa.gov (8.11.6/8.11.6) with ESMTP id g84K7Be28561 for ; Wed, 4 Sep 2002 13:07:11 -0700 Message-Id: <200209042007.g84K7Be28561@math.jpl.nasa.gov> X-Mailer: exmh version 2.4 06/23/2000 with nmh-1.0.4 X-Exmh-Isig-CompType: comp X-Exmh-Isig-Folder: Fortran/WG5 To: SC22WG5@dkuug.dk Subject: Re: John Reid's notes (SC22WG5.2544) SC22 meeting Mime-Version: 1.0 Content-Type: text/plain Date: Wed, 04 Sep 2002 13:07:11 -0700 From: Van Snyder In (SC22WG5.2544), John Reid remarked that other languages are beginning to allow international characters in identifiers. I'm not convinced this is possible in Fortran, as the lexer and parser sometimes don't know where an identifier is until the end of a statement is reached, so it may not be possible to know when to switch alphabets. If this could be allowed, care must be taken in doing so, so as not to allow more than one set to be in use at one time. The reason is that characters that have different encodings in different parts of ISO-10646 have the same appearance. Consider Latin B, Russian B (named "vuh") and Greek B (named "veeta" -- digression: we say "beta", but the Latin/English "b" sound is written in Greek as mu pi). If I write identifiers BBB (Latin, Latin, Latin) and BBB (Latin, Greek, Russian), are they the same or different? If they're different, this represents an enormous opportunity to multiply maintenance costs by a large factor, and leads one to suspect the proposal originally arose in the International Brotherhood of Maintenance Programmers. It's bad enough allowing O and 0 in the same identifier. In any case, at this time, allowing other than the invariant set of ISO-646 goes against the guidelines proposed in the fourth edition of ISO/IEC JTC1/SC22 TR 10176 "Guidelines for the preparation of programming language standards," which is the subject of a current DTR ballot (paper JTC1 -- NOT WG5! -- N6815). In 4.1.3.1.1, it says "As far as possible, the language should be defined in terms only of the characters included within ISO/IEC 646, avoiding use of any that are in national use positions." It goes on to say "The guideline relates to the need for international interchange of programs, and hence is based on the principle of using a minimal set of characters which can be expected to be common to all systems likely to use the programs." I also agree with Richard's reservations about UTF-16. Many years ago, CDC had a "6-12" encoding system. There were very complicated rules to compute the length of a character literal (actually a Hollerith literal at that time). It was a mess that I don't want to duplicate. It is remotely possible that strenuous pondering of the issue may find a way to support it, but I, for one, don't want to hurt myself in trying. Besides, I have a long list of stuff I'd rather do. -- Van Snyder | What fraction of Americans believe vsnyder@math.jpl.nasa.gov | Wrestling is real and NASA is fake? Any alleged opinions are my own and have not been approved or disapproved by JPL, CalTech, NASA, Sean O'Keefe, George Bush, the Pope, or anybody else.