Topic: cons + eval

[kruuger]

hi
not sure how to properly type the subject but here is the issue
pseudo code which i want to execute.

we have subroutine _sum
than list of dotted pairs lst
now i want to go thru this list (assoc) and look for SearchFor.
if founded than eval correct _sum

Code: [Select]

(defun _sum (a b) (+ a b))


(setq lst
  (list
    (cons "One"   '(_sum 1 1))
    (cons "Two"   '(_sum 2 2))
    (cons "Three" '(_sum 3 3))
  )
)

(setq SearchFor "Two")

(if (setq res (assoc SearchFor lst))
  (ok so (eval (cdr res)) to run (_sum 2 2))
  (wrong)
)hope it is clear
thanks
kruuger

[VovKa]

what is the question?

[Grrr1337]

I think this is what you're asking:

Code - Auto/Visual Lisp: [Select]

1. (defun _sum (a b) (+ a b))
2.  
3. (setq lst
4.   (list
5.     (cons "One"   '(_sum 1 1))
6.     (cons "Two"   '(_sum 2 2))
7.     (cons "Three" '(_sum 3 3))
8.   )
9. )
10.  
11. (setq SearchFor "Two")
12.  
13. (or
14.   (eval (cdr (assoc SearchFor lst)))
15.   (princ "\nWrong.")
16. ); or

or access the item as a symbol (lazy way):

Code - Auto/Visual Lisp: [Select]

1. (or
2.   (eval
3.     (cdr
4.       (assoc 'Two '( (One _sum 1 1) (Two _sum 2 2) (Three _sum 3 3) ) )
5.     )
6.   )
7.   (princ "\nWrong")
8. );or

[Lee Mac]

Since the list does not contain variable data, the entire list may be quoted as a literal e.g.:

Code - Auto/Visual Lisp: [Select]

1. (defun _sum ( a b ) (+ a b))
2.  
3. (setq lst
4.    '(
5.         ("One"   _sum 1 1)
6.         ("Two"   _sum 2 2)
7.         ("Three" _sum 3 3)
8.     )
9. )
10. (if (setq expr (cdr (assoc "Two" lst)))
11.     (eval expr)
12.     (princ "\nNot found.")
13. )

Alternatively:

Code - Auto/Visual Lisp: [Select]

1. (defun _sum ( a b ) (+ a b))
2.  
3. (setq lst
4.    '(
5.         ("One"   1 1)
6.         ("Two"   2 2)
7.         ("Three" 3 3)
8.     )
9. )
10. (if (setq args (cdr (assoc "Two" lst)))
11.     (apply '_sum args)
12.     (princ "\nNot found.")
13. )

[kruuger]

omg    not sure why i expect cons this format to work with assoc:
("Two" . _sum 2 2)
and stop testing routine my routine. it looks like all was almost done.
thanks guys, all works fine.