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From: rose@think.ARPA (John Rose)
Newsgroups: net.lang.c
Subject: Re: Pointers to freshly minted functions
Message-ID: <4954@think.ARPA>
Date: Fri, 11-Apr-86 10:18:19 EST
Article-I.D.: think.4954
Posted: Fri Apr 11 10:18:19 1986
Date-Received: Sun, 13-Apr-86 07:43:19 EST
References: <728@petsd.UUCP> <1486@devwrl.DEC.COM>
Reply-To: rose@think.UUCP (John Rose)
Followup-To: net.lang.c
Distribution: net
Organization: Thinking Machines, Cambridge, MA
Lines: 25
Summary: Submitted code creates new functions on the Vax

I have posted to net.sources a small utility which allows creation
of new functions, called ``closures''.  I've already posted this
code, at the end of a lengthy article on closures in Lisp and C,
but I suspect that few people made it to the end of that article.
So, since the topic is still alive, and for the sake of concreteness,
you can look at the code.  Here's an example of what it can do:

typedef double (*PFD)();
extern PFD make_myexp(/* double base */);
/* make_myexp is implemented with malloc, _init_closure,
 * and a `base function' which calls exp. */

PFD Exp, Exp10, Exp2;

/* Each call mallocs a new function object: */
Exp = make_myexp(2.71828183);
Exp10 = make_myexp(10.0);
Exp2 = make_myexp(2.0);

/* Now, pow(x,10.0) == (*Exp10)(x) == Exp10(x) */
-- 
----------------------------------------------------------
John R. Rose		     Thinking Machines Corporation
245 First St., Cambridge, MA  02142    (617) 876-1111 X270
rose@think.arpa				  ihnp4!think!rose