Re: [DOC] About Lisp Data Types

[<tomas@tuxteam.de>]

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On Sun, Aug 01, 2021 at 03:00:16PM +0200, Kevin Vigouroux via Users list for the GNU Emacs text editor wrote:
> I agree with you. Unfortunately, some parts of the explanation are
> unclear or missing.
> 
>     In other languages, an expression is text; it has no other form.  In
>     Lisp, an expression is primarily a Lisp object and only secondarily the
>     text that is the object’s read syntax.  Often there is no need to
>     emphasize this distinction, but you must keep it in the back of your
>     mind, or you will occasionally be very confused.
> 
> • An expression is a Lisp object which gives its meaning.

Well, not really. An expression is something abstract. It can be
represented as a Lisp object. So the expression

  (+ 12 x)

is represented by the list

  ('+ 12 'x)

(now let's gloss over the fact that '+ is just a shorthand for (quote +)
and so on)

So a list of the symbol +, the number 12 and the symbol x.

An expression can be evaluated: then it corresponds to a value. The
value falling out from that evaluation depends on things (for the
example above, it will depend on the current values assigned to +
and x).

> • An expression cannot be understood in its original form (text).

I don't understand what you want to say here: cannot be understood
by whom? A person? A computer program? Which one?

> It makes no sense at first.

If you show me a piece of Hindi text written in Devanagari, I'll
be unable to make heads or tails of it. But this is due to my
lack of culture, not to the writing or language themselves.

This sounds like a stupid remark, but what I want to hint at is,
that if you don't specify context, it is difficult to understand
what you are after.

Cheers
 - t

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