how to access elements of structs that in array

Question

ı want to create new node for huffnode structure,

(defstruct huffnode

  item
   left 
   right

) 

(setq huffroot (make-huffnode :item huffnode-item (aref arr3 (- (length arr3) 1))
                :left (aref arr3 (-  (length arr3) 1))
                :right (aref arr3 (-  (length arr3) 1))))

i need to get elements from arr3 that stores huffnode nodes, how can i access their data,and copy them to huffroot data

Answer 1

Your question is confused in its grammar so it's not clear what you are asking.

You access elements of an array with aref and the slots of a structure with their accessors which are (by default) automatically generated from the struct name and slot name e.g. (huffnode-item x) gets (or when used as the target of a setf sets) the value of the item slot of your huffnode struct stored in x

; SLIME 2.26
CL-USER> (defstruct huffnode item left right)
HUFFNODE
CL-USER> (defvar *huffroot* (make-huffnode :item "foo" :left nil :right nil))
*HUFFROOT*
CL-USER> (setf (huffnode-item *huffroot*)
           (aref arr3 0)
           (huffnode-left *huffroot*)
           (aref arr3 1)
           (huffnode-right *huffroot*)
           (aref arr3 2)