From: Hong Bae Kim
Subject: how to force evaluation of a list?
Date: 
Message-ID: <gCz9a.6483$Or5.765926@news20.bellglobal.com>
Hi

Let's say I have z defined as follows:

> (define z '(+ 1 2))

then z will point to the list (+ 1 2)
so when I type z at the prompt, I get

> z
(+ 1 2)

But now I want to evaluate this list. How do I do it?
From: Henrik Motakef
Subject: Re: how to force evaluation of a list?
Date: 
Message-ID: <873cm1vyuw.fsf@interim.henrik-motakef.de>
"Hong Bae Kim" <········@sympatico.ca> writes:

> But now I want to evaluate this list. How do I do it?

Use EVAL:
http://www.lispworks.com/reference/HyperSpec/Body/f_eval.htm

hth
Henrik
From: Larry Hunter
Subject: Re: how to force evaluation of a list?
Date: 
Message-ID: <m3u1egbglk.fsf@huge.uchsc.edu>
Hong Cae Kim asks:

 > (define z '(+ 1 2))
 > z
 (+ 1 2)
 But now I want to evaluate this list. How do I do it?

Well, "define" suggests scheme and not (Common) lisp, but there are
two possible answers depending on what exactly you meant.

1. Don't quote the expression you want to evaluation. ' means "don't
   evaluate what comes next."

   > (define z (+ 1 2))
   > z
   3

2. If you are trying to programmatically construct code, and then want
   to evaluated what you constructed, you can use the function "eval"
   as in:

   > (define z '(+ 1 2))
   > (eval z)
   3

   But this is rarely what people new to lisp (or scheme) really want
   to be doing.

Larry

-- 

Lawrence Hunter, Ph.D.
Director, Center for Computational Pharmacology
Associate Professor of Pharmacology, PMB & Computer Science

phone  +1 303 315 1094           UCHSC, Campus Box C236    
fax    +1 303 315 1098           School of Medicine rm 2817b   
cell   +1 303 324 0355           4200 E. 9th Ave.                 
email: ············@uchsc.edu    Denver, CO 80262       
PGP key on public keyservers     http://compbio.uchsc.edu/hunter
From: Kaz Kylheku
Subject: Re: how to force evaluation of a list?
Date: 
Message-ID: <cf333042.0303060125.75f45d9b@posting.google.com>
"Hong Bae Kim" <········@sympatico.ca> wrote in message news:<·····················@news20.bellglobal.com>...
> Hi
> 
> Let's say I have z defined as follows:
> 
> > (define z '(+ 1 2))

Then you are programming in Scheme, not Lisp. The comp.lang.scheme
newsgroup is down the hall, to your left.

> then z will point to the list (+ 1 2)
> so when I type z at the prompt, I get
> 
> > z
> (+ 1 2)
> 
> But now I want to evaluate this list. How do I do it?

In Lisp or Scheme, this will work:

  (eval z)

In Lisp, you could also use this trick: make z a symbol-macro. Then
the symbol z is automatically replaced by the specified expansion,
which is evaluated in its place:

  (define-symbol-macro z '(+ 1 2))
  z
  ==> 3
comp.lang.lisp / 2003 / mar