contains.rkt

#lang racket/base

;;;; This file has been changed from its original dharmatech/mpl version.

(provide contains?
        this-contains?
        contains-this?
        free?
        is-free?
        free-of?)

(require (only-in srfi/1 any))

(define (contains-this? t)
  (lambda (u)
    (contains? u t)))

(define (this-contains? u)
  (lambda (t)
    (contains? u t)))

(define (contains? u t)
  (or (equal? u t)
      (and (list? u)
           (any (contains-this? t) u))))

(define (free? u t)
  (not (contains? u t)))

(define (is-free? u)
  (lambda (t)
    (free? u t)))

(define (free-of? t)
  (lambda (u)
    (free? u t)))