;;; File:
;;;   searching.scm
;;; Authors:
;;;   Samuel A. Rebelsky
;;;   The denizens of CSC151.02 2003F
;;; Summary:
;;;   A variety of procedures for searching lists and vectors.

;;; Procedure:
;;;   search-vector
;;; Parameters:
;;;   vec, a vector
;;;   pred? a predicate
;;; Purpose:
;;;   Find a value in vec for which pred? holds.
;;; Produces:
;;;   pos, the index of vec in which a value that matches pred? resides
;;; Preconditions:
;;;   pred? must be applicable to every element in vec
;;; Postconditions:
;;;   pos is an integer
;;;   If pred? holds for no element of vec, pos is -1.
;;;   If pred? holds for an element of vec,
;;;     pos is a valid index (<= 0 pos (- (vector-length vec) 1))
;;;     (pred? (vector-ref vec pos)) holds (is not #f)
;;; Pstrategy:
;;;   Recursive kernel keeps track of position
;;;   Position starts at high value and drops down
(define search-vector
  (lambda (pred? vec)
    (letrec ((kernel
               (lambda (pos)
                 (cond
                   ((< pos 0) -1)
                   ((pred? (vector-ref vec pos)) pos)
                   (else (kernel (- pos 1)))))))
      (kernel (- (vector-length vec) 1)))))

;;; Procedure:
;;; Parameters:
;;; Purpose:
;;; Produces:
;;; Preconditions:
;;; Postconditions:

;;; Procedure:
;;; Parameters:
;;; Purpose:
;;; Produces:
;;; Preconditions:
;;; Postconditions: