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(define (true? expr) (eq? expr 'true))
(define (false? expr) (eq? expr 'false))
(define (bool? expr)
(or (true? expr)
(false? expr)))
(define (and-special . items)
(if (null? items)
'false
(let ([first (car items)])
(cond
[(true? first) (apply and-special (cdr items))]
[(false? first) 'false]
[else (error "AND: unable to evaluate non-boolean form" first)]))))
(define (or-special . items)
(if (null? items)
'false
(let ([first (car items)])
(cond
[(true? first) 'true]
[(false? first) (apply or-special (cdr items))]
[else (error "OR: unable to evaluate non-boolean form" first)]))))
(define (not-fn x) (not (true? x)))
(define primitives
`((+ . ,+)
(- . ,-)
(* . ,*)
(&& . ,and-special)
(|| . ,or-special)
(/= . ,not-fn)))
(define (primitive-names) (map car primitives))
(define (primitive-objs) (map cdr primitives))
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