structural-each-plus-others.rkt

#lang racket/base

(require racket/match)

(define (each+others/non-index cs [prev '()] [res '()])
  (match cs
    ['() res]
    [(cons c cs) (each+others/non-index cs
                                        (cons c prev)
                                        (cons (cons c (append prev cs)) res))]))
                                        
;; example:
;; > (each+others/non-index (string->list "hello"))
;; '((#\o #\l #\l #\e #\h) (#\l #\l #\e #\h #\o) (#\l #\e #\h #\l #\o) (#\e #\h #\l #\l #\o) (#\h #\e #\l #\l #\o))