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From: oz@yunexus.yorku.ca (Ozan Yigit)
Newsgroups: comp.lang.misc
Subject: Re: On whether C has first-class composable functions
Keywords: first-class, scheme
Message-ID: <20021@yunexus.YorkU.CA>
Date: 8 Jan 91 18:27:19 GMT
References: <1990Dec29.110202.3862@mathrt0.math.chalmers.se> <17557:Jan219:22:3191@kramden.acf.nyu.edu> <442@data.UUCP> <4408:Jan421:44:3391@kramden.acf.nyu.edu>
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In article <4408:Jan421:44:3391@kramden.acf.nyu.edu> 
brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:

>In article <442@data.UUCP> kend@data.UUCP (Ken Dickey) writes:
>> There is an important property of "first-class" objects missing here.
>> A first-class object does not have to be named.

>Do you have a reference? As always, I'm doing my best to use standard
>terminology; I just haven't seen any references that demand a syntactic
>restriction like that.

There may be many references, though I am not sure if that will that make
any difference whatsoever. It appears that you would prefer to argue than
to look them up.

Here is one: William Clinger, Semantics of Scheme, February. 1988, BYTE,
             pp. 221-227

[Will Clinger is an author of MacScheme, one of the nicest [I think]
implementations of this language.]

   First-Class Objects
   
   All Scheme objects are endowed with certain inalienable rights:
   
   o Objects have the right to remain anonymous.
   o Objects have an identity that is independent of any names by
     which they may be known 
   o Objects can be stored in variables and in data structures without
     losing their identity
   o Objects may be returned as a result of a procedure call
   o Objects never die.
   
   All scheme objects are first-class citizens of the language. In most
   programming languages, the only first-class objecst are those that can
   easily fit into a machine register, like numbers, booleans, and
   pointers.  While numbers may be used without being given names,
   procedures may not; while characters and pointers may be stored,
   strings may not; while booleans live forever, vectors may die when the
   procedure that created them returns. Thus, Scheme is very unusual in
   this respect. In fact, Scheme is the most widely used procedural
   language in which all objects are first class.

     Though objects never die, they may become inaccessible and therefore
   useless. Implementations of Scheme and other advanced languages may in
   fact reclaim the storage occupied by an object, provided they can prove
   that the object will never again be used. Algorithms for performing
   these proofs are known as garbage-collection algorithms.
   

... next !!

oz
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