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From: manheime@nbs-amrf.UUCP (Ken Manheimer)
Newsgroups: net.emacs
Subject: Re: Re: MLisp in Gosling's
Message-ID: <375@nbs-amrf.UUCP>
Date: Sun, 3-Aug-86 23:53:05 EDT
Article-I.D.: nbs-amrf.375
Posted: Sun Aug  3 23:53:05 1986
Date-Received: Mon, 4-Aug-86 07:26:09 EDT
References: <1514@vax135.UUCP> <916@unirot.UUCP> <371@nbs-amrf.UUCP> <2713@umcp-cs.UUCP>
Organization: National Bureau of Standards
Lines: 43

> In article <371@nbs-amrf.UUCP> manheime@nbs-amrf.UUCP (Ken Manheimer) writes:
> >The binding scheme is important.  [The one in MLisp] can be
> >very insidious and have enourmous impact on applications.
> >You lose recursion ... to the Mlisp binding bug.
> 
> Actually, it *is* possible to write recursive routines.  You have
> to use a two-stage argument evaluation method:
> 
> 	(defun foo $foo-arg1
> 	    (setq $foo-arg1 (arg 1))
> 	    (progn $foo-local-var
> 		(setq $foo-local-var $foo-arg1)
> 		...))
> -- 
> In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
> UUCP:	seismo!umcp-cs!chris
> CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu

You might as well just forget explicitly passing the value to the
subordinate invocation of the function and instead call a helper
function that uses a single "state" variable over the duration of
its multiple incursions.

Eg:

(defun fooMain $foo-arg
   (setq $foo-arg (arg 1))
   (...)	;;; miscellaneous foo preparation
   (fooHelper))
(defun fooHelper
   (xxx $foo-arg)	;;; miscellaneous operations on/wrt $foo-arg
   (if (fooPred $foo-arg)
       (fooHelper))
   ...)

I think you can do the same thing in fortran (?).  I'd hate to write
a substantial suite of programs where you had to worry about this
kind of finagling, though.  (Come to think of it, i have done a lot of
hacking on, um, rmail, info, ..., and this certainly was at times
a pain.  Doable, but not pleasant, and it certainly engenders a
weird contortion to the code...)

Ken.			...!seismo!nbs-amrf!manheime