From: Alex S. Crain
Subject: Re: Survey question
Date:
Message-ID: <1373@umbc3.UMD.EDU>
In article <·····@bu-cs.BU.EDU> ······@bu-cs.BU.EDU (Robert Muller) writes:
> What type of object is read in:
>> (read)
>(lambda (x) x)
A list, specifically (LAMBDA . ((X . nil) . (X . nil)))
--
:alex.
Systems Programmer
···········@umbc3.umd.edu UMBC
····@umbc3.umd.edu
From: Michael Sokolov
Subject: Re: Survey question
Date:
Message-ID: <3320@mit-amt>
>(setq foo (read))
>(lambda (x) x)
I think the question was what type of object is foo bound to?
I think it is basically just a list. (fboundp 'foo) returns nil.
however, (funcall foo 1) does return 1. Accordingly, (functionp foo)
returns t. I discovered that (functionp 'bar) also returns t, in spite
of the fact that bar was previously unbound: anyone know why?
MS
In article <····@mit-amt> ·······@media-lab.media.mit.edu (Michael Sokolov) writes:
>>(setq foo (read))
>>(lambda (x) x)
> I think the question was what type of object is foo bound to?
>I think it is basically just a list. (fboundp 'foo) returns nil.
Since READ doesn't call EVAL it is just returning a cons. If you need
to have the arguments evaled then you have to write (eval (read)).
That would cause an error in the above example, since LAMBDA is not
a function.
>however, (funcall foo 1) does return 1. Accordingly, (functionp foo)
>returns t. I discovered that (functionp 'bar) also returns t, in spite
>of the fact that bar was previously unbound: anyone know why?
FUNCTIONP only says whether its argument is suitable to passed to FUNCALL,
which is true of all symbols. If you want to find out if a symbol has a
global function definition attached to it you have to use FBOUNDP.
There was some discussion a while back -- though I think it may have been
in the KCl list -- as to what the point of FUNCTIONP was. I think it was
generally agreed that it was pretty pointless. I don't recall whether
X3J13 was planning on rethinking it or not -- perhaps someone from there
might fill us in on the latest update.