Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!rpi!sci.ccny.cuny.edu!phri!marob!cowan
From: cowan@marob.masa.com (John Cowan)
Newsgroups: comp.lang.lisp
Subject: Re: Why aren't CL functions 1st class objects?
Message-ID: <26FE4FEF.48AE@marob.masa.com>
Date: 24 Sep 90 18:26:54 GMT
References: <1990Sep13.202219.21047@oracle.com> <3437@skye.ed.ac.uk> <3806@goanna.cs.rmit.oz.au>
Organization: ESCC, New York City
Lines: 32

In article <3806@goanna.cs.rmit.oz.au>,
	ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
>In article <3437@skye.ed.ac.uk>, jeff@aiai.ed.ac.uk (Jeff Dalton) writes:
>>    - All objects can be the arguments of procedures.
>>    - All objects can be returned as the results of procedures. 
>>    - All objects can be the subject of assignment statements.
>>    - All objects can be tested for equality.
>
>[T]here is something clearly wrong with this list, because C can
>satisfy it, and functions aren't first-class in C.  In C, a pointer to
>a function can be passed to a procedure, returned from a procedure,
>assigned to a variable, or compared for equality to another pointer of
>the same type.

This blurs the rigid distinction C makes between functions and pointers-to-
functions.  A pointer-to-function is a first-class C object; a function is
not.

>What's C missing?  The ability to create (possibly) new functions at run time.

That's not enough.  There is no ability in Lisp to create "new" integers
at run time; conceptually all the integers already exist.  Ditto with all
the characters.

You cannot have a function in C that accepts a function as an argument
or returns a function as a value.  Nor can you assign functions.
ANSI C relaxes the rules a little so that you can use the same syntax to
call a function specified by name or by a pointer-to-function, but the
two things are still different, and functions are very much 2nd-class.
-- 
cowan@marob.masa.com			(aka ...!hombre!marob!cowan)
			e'osai ko sarji la lojban