University
of Washington • CSE583 • D. Notkin © 2000
23
Equality
lThere are (more than) two different notions of equality in Scheme (and most other programming languages)
–Are the two entities isomorphic? (equal?)
–Are they the exact same
entity? (eqv?)
l(eqv? 3 3) ® #t
l(eqv? ’(3
4) ‘(3 4))® #f l(let ((x ‘(3 4)))
(eqv? x x) ® #t l(equal? ’(3 4) ‘(3 4))
® #t
l(eqv? “hi”
“hi”) ® #f
l(equal?
“hi” “hi”) ® #t
l(eqv? ‘hi
‘hi) ® #t
l(eqv? ()
()) ® #t