Path: news.daimi.aau.dk!news.uni-c.dk!uninett.no!nntp.uio.no!newsfeed.nacamar.de!fu-berlin.de!news-ber1.dfn.de!news-ham1.dfn.de!news-han1.dfn.de!news-koe1.dfn.de!ilex.fernuni-hagen.de!news From: Arnd Poetzsch-Heffter Newsgroups: comp.lang.beta Subject: Is overwriting possible in BETA? Date: Mon, 09 Jun 1997 13:52:58 +0200 Organization: FernUniversitaet Hagen Lines: 37 Message-ID: <339BEE9A.B0F69DF@fernuni-hagen.de> NNTP-Posting-Host: pcpoet1.fernuni-hagen.de Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (X11; I; Linux 2.0.25 i586) Xref: news.daimi.aau.dk comp.lang.beta:11136 Hello! Is it possible in BETA to overwrite an attribute of a superpattern within a subpattern? Consider e.g. the following fragment (as I have no BETA execution environment, the fragment might contain some syntax errors, sorry for that): Super: (# Attr :< SuperAttrPattern { or: Attr : SuperAttrPattern } #); Sub : Super (# Attr : SomePattern_Not_Subpattern_Of_SuperAttrPattern; #) Such a situation is often useful to refine implementations (E.g. to refine a singly linked list implementation where the list length is computed by a recursive procedure pattern to an implementation where the length is stored with each element). If overwriting is not allowed in BETA, why is BETA that strict? Thanks in advance for your answers. Best regards, Arnd Poetzsch-Heffter _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ _/ _/ Prof. A. Poetzsch-Heffter tel: ++49 2331 987 2172 _/ LG Prakt. Informatik V _/ FernUniversit"at email: poetzsch@fernuni-hagen.de _/ D-58084 Hagen URL: http://voss.fernuni-hagen. _/ de/pi5/pi5.html