Question

Input1:

(decompose '(* 1 2 3 4))

Output1:

'(* 1 (* 2 (* 3 4)))

Input2

(decompose '(+ 1 2 3 (* 5 6 7)))

Output2

'(+ 1 (+ 2 (+ 3 (* 5 (* 6 7)))))    

Does anyone have ideas about this?

Answer 1

Same way as you would evaluate it, but instead of outputting the result, you simply output the expression that would be used.

Here’s my implementation, tested on Racket:

(define (decompose expr)
  (define (expand x)
    (if (list? x)
        (decompose x)
        x))
  (define oper (car expr))
  (let next ((args (map expand (cdr expr))))
    (if (<= (length args) 2)
        (cons oper args)
        (list oper (car args) (next (cdr args))))))