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@tungurlakachakcak
Created September 23, 2019 22:56
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Expression eval in Racket
; Small interpreter
; (Const (Add 1 (Add-v 2 3))) = 6
(define (Const? x) (eq? x `Const))
(define (Add? x) (eq? x `Add))
(define (eval_expr exp)
(cond [(Const? (car exp))
(if (number? (cdr exp))
(cdr exp)
(eval_expr (cdr exp)))]
[(Add? (car exp))
(if (number? (car (cdr exp)))
(if (number? (cdr (cdr exp)))
(+ (car (cdr exp)) (cdr (cdr exp)))
(+ (car (cdr exp)) (eval_expr (cdr (cdr exp)))))
(if (number? (cdr (cdr exp)))
(+ (eval_expr (car (cdr exp))) (cdr (cdr exp)))
(+ (eval_expr (car (cdr exp))) (eval_expr (cdr (cdr exp))))))]))
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