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From: jar@ZOHAR.AI.MIT.EDU (Jonathan Rees)
Newsgroups: comp.lang.scheme
Subject: unspecified-object
Message-ID: <8905241845.AA02829@zohar>
Date: 24 May 89 18:45:58 GMT
References: <24169@shemp.CS.UCLA.EDU>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: jar@zurich.ai.mit.edu
Organization: The Internet
Lines: 15


   Date: 23 May 89 01:51:40 GMT
   From: pierce@locus.ucla.edu

      I think that the specification of Scheme, as well as many Scheme programs,
      would be made more elegant if an "unspecified-object" analogous to NaN in 
      the IEEE numeric standard were introduced. Functions which return 
      unspecified values now would be required to return an "unspecified-object"
      instead.

It doesn't make sense to specify that the object to be returned should
be unspecified.  It seems to me that if some specific object is to be
specified, then it should be a specific object, not an unspecific one.
Besides, if we specify what object should be returned, then that
object will no longer be unspecified.