Another code review perhaps?

[B. Pym]

Define iterative and recursive versions of a function that takes an
object x and a vector v, and returns a list of all the objects that
immediately precede x in v.

(defun precedes (object vector)
(loop for x across vector
and i from 0
when (and (equal x object) (> i 0))
collect (elt vector (1-i))))

Look at that:

(1-i)

Don't you think that that should be:

(1- i)

or

(- i 1)

?

It's shorter when you use a Lispy language instead of CL.

Gauche Scheme

(use srfi-42) ; list-ec

(define (precedes obj vec)
(list-ec (: x (index i) vec)
(if (and (> i 0) (equal? x obj)))
(ref vec (- i 1))))

(precedes 5 #(5 0 4 5 8 9 5))
===>
(4 9)

Another way:

(define (precedes o v)
(let ((l (vector->list vec)))
(filter-map
(^(a b) (and (equal? o a) b))
(cdr l)
l)))

[Kaz Kylheku]

Post by B. Pym

Define iterative and recursive versions of a function that takes an
object x and a vector v, and returns a list of all the objects that
immediately precede x in v.

(defun precedes (object vector)
(loop for x across vector
and i from 0
when (and (equal x object) (> i 0))
collect (elt vector (1-i))))

(1-i)
(1- i)
or
(- i 1)
?
It's shorter when you use a Lispy language instead of CL.
Gauche Scheme
(use srfi-42) ; list-ec
(define (precedes obj vec)
(list-ec (: x (index i) vec)
(if (and (> i 0) (equal? x obj)))
(ref vec (- i 1))))
(precedes 5 #(5 0 4 5 8 9 5))
===>
(4 9)
(define (precedes o v)
(let ((l (vector->list vec)))
(filter-map
(^(a b) (and (equal? o a) b))
(cdr l)
l)))

1> (match @(scan-all (@x 5 . @nil)) '(5 0 4 5 8 9 5) x)
(4 9)
2> (window-mappend 1 nil (do if (and @1 (= @2 5)) (list @1)) #(5 0 4 5 8 9 5))
#(4 9)