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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) x))
#f)))
(define (make-composed-comparator type-test . comparators)
(make-comparator
type-test
(if (every comparator-equality-predicate comparators)
(lambda (a b)
(every (lambda (cmp)
((comparator-equality-predicate cmp) a b))
comparators))
#f)
(if (every comparator-ordering-predicate comparators)
(lambda (a b)
(let ((gen (list->generator comparators)))
(let loop ((cmp (gen)))
(cond ((eof-object? cmp) #f)
(((comparator-ordering-predicate cmp) a b) #t)
(((comparator-equality-predicate cmp) a b) (loop (gen)))
(else #f)))))
#f)
(if (every comparator-hash-function comparators)
(lambda (x)
(generator-fold bitwise-xor
0
(gmap (lambda (cmp)
((comparator-hash-function cmp) x))
(list->generator comparators))))
#f)))
(define-syntax compose-comparator
(syntax-rules ()
((_ type-test (unwrap . more) ...)
(make-composed-comparator
type-test
(let-values (((unwrap cmp) (compose-comparator-form unwrap . more)))
(make-wrapper-comparator
(comparator-type-test-predicate cmp)
unwrap
cmp)) ...))))
(define-syntax compose-comparator-form
;; Using this submacro enables enforcement of the correct form with
;; moderately more useful syntax errors than doing it the SRFI 9
;; way, at least within the limited bounds of what one can do for
;; that in syntax-rules.
(syntax-rules ()
((_ unwrap) (compose-comparator-form unwrap (make-default-comparator)))
((_ unwrap cmp)
(values
unwrap cmp))))
(define (comparison-procedures comparator)
(values
(lambda args (apply <? comparator args))
(lambda args (apply <=? comparator args))
(lambda args (apply =? comparator args))
(lambda args (apply >=? comparator args))
(lambda args (apply >? comparator args))))
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