I've followed this discussion and thought I understood it quite well until I tried it. Following are my results, using Racket 3.3 on Windows XP:
Test 1: #lang racket (define-struct posn (x y)) (define x (make-posn 4 5)) (define y (make-posn 4 5)) (define z y) > (equal? x y) #f > (eq? x y) #f > (eqv? x y) #f > (equal? x z) #f > (equal? y z) #t > (eq? x z) #f > (eq? y z) #t Contrary to my understanding of what several commenters have said equal? eq? and eqv? all give #f when comparing x & y equal? and eq? both give #t when comparing y & z Test 2: #lang racket (define-struct posn (x y) #:transparent) (define x (make-posn 4 5)) (define y (make-posn 4 5)) (define z y) > (equal? x y) #t > (eq? x y) #f > (equal? x z) #t Adding #:transparent to the posn struct definition makes x equal? to both y and z as it should, and eq? gives #f when comparing x and y as it should.
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