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;;; The sort package -- sorted predicates
;;; Olin Shivers 10/98.
;;;
;;; (list-sorted? < lis) -> boolean
;;; (vector-sorted? < v [start end]) -> boolean
(define (list-sorted? < list)
(or (not (pair? list))
(let lp ((prev (car list)) (tail (cdr list)))
(or (not (pair? tail))
(let ((next (car tail)))
(and (not (< next prev))
(lp next (cdr tail))))))))
(define (vector-sorted? elt< v . maybe-start+end)
(call-with-values
(lambda () (vector-start+end v maybe-start+end))
(lambda (start end)
(or (>= start end) ; Empty range
(let lp ((i (+ start 1)) (vi-1 (vector-ref v start)))
(or (>= i end)
(let ((vi (vector-ref v i)))
(and (not (elt< vi vi-1))
(lp (+ i 1) vi)))))))))
;;; Copyright and porting non-notices
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Give me a break. It's fifteen lines of code. I place this code in the
;;; public domain; help yourself.
;;;
;;; If your Scheme has a faster mechanism for handling optional arguments
;;; (e.g., Chez), you should definitely port over to it. Note that argument
;;; defaulting and error-checking are interleaved -- you don't have to
;;; error-check defaulted START/END args to see if they are fixnums that are
;;; legal vector indices for the corresponding vector, etc.
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