Xref: utzoo comp.object:553 comp.lang.c++:5733
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From: twl@brunix (Ted "Theodore" (W) Leung)
Newsgroups: comp.object,comp.lang.c++
Subject: Re: Continuations
Message-ID: <21989@brunix.UUCP>
Date: 1 Dec 89 17:19:49 GMT
References: <2664@bingvaxu.cc.binghamton.edu> <9624@pyr.gatech.EDU> <1623@odin.SGI.COM> <1989Nov28.183816.15252@odi.com> <9964@june.cs.washington.edu> <1989Nov29.225826.19483@odi.com> <10008@june.cs.washington.edu>
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Reply-To: twl@boojum.UUCP (Ted "Theodore" (W) Leung)
Organization: Brown University Department of Computer Science
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In article <10008@june.cs.washington.edu> peterd@june.cs.washington.edu (Peter C. Damron) writes:
>4. C and C++ have first class functions.  Functions can be passed as
>   parameters, returned as function values, and assigned to variables.
>   The reason that C and C++ do not allow nested functions is precisely
>   so that they can have first-class functions implemented on a stack
>   (e.g. no closure required).  The "parent block" of a function is
>   simply the global variables.
>
It seems like it would be useful to make a distinction between "first
class" functions which require their implementation via a closure, and
those which do not.  There is a fairly standard trick in the Scheme
community, which uses closures to create objects.  The closed over
variables are used to represent the local state of the object, and the
code of the closure is a big case statement which selects the correct
method to be invoked.  It seems to me that you cannot use C "first class"
functions to create objects, because they have no closure.....

I do think that C/C++ functions are not first class because it is not
possible to create a function on the fly the way that you can in LISP
or Scheme.

Ted

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