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RE: [External] : Re: Which Elisp types are mutable?


From: Drew Adams
Subject: RE: [External] : Re: Which Elisp types are mutable?
Date: Sat, 5 Jun 2021 20:17:34 +0000

> > Symbols are probably a weird case terminology-wise.  Here I define "mutable
> symbol" as symbol whose value and function slots can be changed (true for
> most symbols except keywords).  However, arguably other definitions are
> possible, depending on whether you see their values and function slots as
> "part of a symbol" or as something they refer to.  (The manual doesn't
> specify this.)
> 
> Ah, I see.  For me, a symbol is one thing, and what is in its
> function/value/properties cells is another.

Do you say the same about a cons cell?  Certainly
the container is one thing and what it contains
is another, in one sense.  That's true of any kind
of container, from a file to a defstruct.

Mutability of list structure is all about changing
the contents (car, cdr) of cons cells.  It has no
other meaning.

Lisp symbols are a kind of object.  They have
attributes, including name, value (as a variable),
function definition, and an unlimited slew of
other attributes: their `symbol-properties'.



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