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(define (make-wrapper-comparator type-test unwrap contents-comparator)
(make-comparator
type-test
(lambda (a b)
((comparator-equality-predicate contents-comparator)
(unwrap a)
(unwrap b)))
(if (comparator-ordering-predicate contents-comparator)
(lambda (a b)
((comparator-ordering-predicate contents-comparator)
(unwrap a)
(unwrap b)))
#f)
(if (comparator-hash-function contents-comparator)
(lambda (x)
((comparator-hash-function contents-comparator)
(unwrap x)))
#f)))
(define (make-product-comparator . comparators)
(if (null? comparators)
comparator-one
(let* ((type-tests
(delete-duplicates
(map comparator-type-test-predicate comparators)
eq?))
(type-test
(lambda (val)
(every (lambda (test) (test val)) type-tests))))
(make-comparator
type-test
(lambda (a b)
(every (lambda (cmp)
((comparator-equality-predicate cmp) a b))
comparators))
(if (every comparator-ordered? comparators)
(lambda (a b)
(let loop ((cmps comparators))
(cond ((null? cmps) #f)
(((comparator-ordering-predicate (car cmps)) a b) #t)
(((comparator-equality-predicate (car cmps)) a b) (loop (cdr cmps)))
(else #f))))
#f)
(if (every comparator-hashable? comparators)
(lambda (x)
(fold bitwise-xor
0
(map (lambda (cmp)
((comparator-hash-function cmp) x))
comparators)))
#f)))))
(define (comparator-index comparators val)
(list-index
(lambda (cmp)
((comparator-type-test-predicate cmp) val))
comparators))
(define (make-sum-comparator . comparators)
(if (null? comparators)
comparator-zero
(make-comparator
(lambda (x)
(any
(lambda (cmp)
((comparator-type-test-predicate cmp) x))
comparators))
(lambda (a b)
(let ((a-cmp-idx (comparator-index comparators a))
(b-cmp-idx (comparator-index comparators b)))
(if (not (= a-cmp-idx b-cmp-idx))
#f
(let ((cmp (list-ref comparators a-cmp-idx)))
((comparator-equality-predicate cmp) a b)))))
(if (every comparator-ordered? comparators)
(lambda (a b)
(let ((a-cmp-idx (comparator-index comparators a))
(b-cmp-idx (comparator-index comparators b)))
(cond ((< a-cmp-idx b-cmp-idx) #t)
((> a-cmp-idx b-cmp-idx) #f)
(else
(let ((cmp (list-ref comparators a-cmp-idx)))
((comparator-ordering-predicate cmp) a b))))))
#f)
(if (every comparator-hashable? comparators)
(lambda (x)
(let ((cmp (find (lambda (cmp) ((comparator-type-test-predicate cmp) x))
comparators)))
((comparator-hash-function cmp) x)))
#f))))
(define comparator-one
(make-comparator
(lambda (x) #t)
(lambda (a b) #t)
(lambda (a b) #f)
(lambda (x) 0)))
(define comparator-zero
(make-comparator
(lambda (x) #f)
(lambda (a b) (error "can't compare" a b))
(lambda (a b) (error "can't compare" a b))
(lambda (x) (error "can't hash" x))))
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