When I execute the following:
(set 'lst '(
(id001 (name "Anne") (addr (country "USA") (city "New York")))
(id002 (name "Jean") (addr (country "France") (city "Paris")))
))
(set 'myargs '('id002 'addr))
;; ('id002 'addr)
(set 'allargs (append '(lst) myargs))
;; (lst 'id002 'addr)
(apply assoc allargs)
I get
Whereas
Yields the expected result.
What is the correct way?
Thanks
Tim
When you have multiple keys only the second parenthesized form will work. The flat from and using 'apply' would only work for one key:
(apply assoc allargs)
=> (id001 (name "Anne") (addr (country "USA") (city "New York")))
In case you have to construct the arguments for the parenthesized multi-key capable form you could do it this way:
(eval (cons assoc allargs))
=> (addr (country "France") (city "Paris"))
But why would you do this, when all elements in the parenthesized form can be variables:
(set 'key2 'addr)
(assoc (lst key1 key2))
=> (addr (country "France") (city "Paris"))
Hi Lutz.
My goal is an interface to a context that manages associative lists
of any level.
Thus, rather than use named variables, I'd like to use (args)
- so think (args) instead of myargs.
Unfortunately, I still can't wrap my brain around _that_ approach.
thanks
tim
Draft attempt to use more of a 'drill-down' approach
(define (hashit)
(catch
(let((res lst))
(doargs (i)
(set 'res (assoc i res))
(if (not res) (throw nil))) ;; dead end
(throw res)) ;; done
'res ;; catch it here
) res) ;; return here