newlispfanclub.alh.net

Posted: **Fri Jun 29, 2007 1:08 pm**

Is it possible to define new types in newlisp?

Posted: **Fri Jun 29, 2007 1:52 pm**

no two symbols in newLISP point to the same, except when pointing to symbols. So if you do:

(set 'x "hello"
(set 'y x) => "hello"

those are two different memory pieces containing "hello". But when doing

Code: Select all

(set 's "content of s")
(set 'x 's) => s
(set 'y x) => s

(eval x) => "content of s"
(eval y) => "content of s"

The two strings are the identical piece of memory, as you can show:

Code: Select all

(pop s) => "c"
(eval x) => "ontent of s"
(eval y) => "ontent of s"

(pop (evall x)) = "o"
(eval y) => "ntent of s"

Is there a way to discover symbols that point to a value?

yes, you still could do this:

Code: Select all

 (set 'x "hello")
 (set 'y "hello")

(filter (fn (s) (= "hello" (eval s))) (symbols)) => (x y)

but of course this is just a linear lookup, nothing is indexed here.

Ooo! A reverse lookup! Interesting idea. Lutz?

yes that would be possible, you could create a reversed index:

Code: Select all

(set 'x "hello")
(set 'y 123)

; create a reverse index in Idx
(map (fn (s) (set (sym (string (eval s)) 'Idx) s )) (symbols))

(context Idx "hello") => x
(context Idx "123") => y

Lutz

newlispfanclub.alh.net

Defining types

Defining types