trying to convert C to Lisp

Question

I am trying to convert this code to lisp code. But don't know how to do it is it right?

for (j=i-1; j>=0 && list[j]>key; j--) {
    list[j+1] = list[j];
}

(loop (set j (- i 1))
  (setq (aref x(+ j 1) (aref x j))
  (setq j (- j 1)
  (when (or(>= j 0)
           (> (aref x j) key)
  (return-from foo 0))

Answer 1

The most straightforward way is to use the extended loop:

(loop :for j :downfrom (1- i)
      :while (and (not (minusp j))
                  (> (aref list j) key))
      :do (setf (aref list (1+ j))
                (aref list j)))

(Note: I prefer to use keywords for loop keywords, because that gives me nice syntax highlighting for free. You will often also find them as plain symbols, e. g. for instead of :for.)

Answer 2

though it's not a word-by-word translation, i would probably go with something like this:

(let* ((data (vector 1 2 3 4 5 6 7 8 9))
       (key 3)
       (pos (or (position-if (lambda (x) (<= x key)) data :from-end t)
                0)))
  (setf (subseq data (1+ pos))
        (subseq data pos))
  data)

Looks more like a CL style to me.