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Diffstat (limited to 'semestr-2/racket/l9z17/solution.rkt')
| -rw-r--r-- | semestr-2/racket/l9z17/solution.rkt | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/semestr-2/racket/l9z17/solution.rkt b/semestr-2/racket/l9z17/solution.rkt new file mode 100644 index 0000000..5e98036 --- /dev/null +++ b/semestr-2/racket/l9z17/solution.rkt @@ -0,0 +1,266 @@ +#lang racket
+
+; Do programming.rkt dodajemy instrukcje
+
+(provide eval-while parse-while env-empty env-lookup)
+
+;;; We współpracy z Kacprem Soleckim
+
+; --------- ;
+; Wyrazenia ;
+; --------- ;
+
+(struct const (val) #:transparent)
+(struct binop (op l r) #:transparent)
+(struct var-expr (id) #:transparent)
+(struct let-expr (id e1 e2) #:transparent)
+(struct letrec-expr (id e1 e2) #:transparent)
+(struct if-expr (eb et ef) #:transparent)
+(struct cons-expr (e1 e2) #:transparent)
+(struct car-expr (e) #:transparent)
+(struct cdr-expr (e) #:transparent)
+(struct null-expr () #:transparent)
+(struct null?-expr (e) #:transparent)
+(struct app (f e) #:transparent)
+(struct lam (id e) #:transparent)
+
+(define (expr? e)
+ (match e
+ [(const n) (or (number? n) (boolean? n) (string? n))]
+ [(binop op l r) (and (symbol? op) (expr? l) (expr? r))]
+ [(var-expr x) (symbol? x)]
+ [(let-expr x e1 e2)
+ (and (symbol? x) (expr? e1) (expr? e2))]
+ [(letrec-expr x e1 e2)
+ (and (symbol? x) (expr? e1) (expr? e2))]
+ [(if-expr eb et ef)
+ (and (expr? eb) (expr? et) (expr? ef))]
+ [(cons-expr e1 e2) (and (expr? e1) (expr? e2))]
+ [(car-expr e) (expr? e)]
+ [(cdr-expr e) (expr? e)]
+ [(null-expr) true]
+ [(null?-expr e) (expr? e)]
+ [(app f e) (and (expr? f) (expr? e))]
+ [(lam id e) (and (symbol? id) (expr? e))]
+ [_ false]))
+
+(define (parse q)
+ (cond
+ [(number? q) (const q)]
+ [(eq? q 'true) (const true)]
+ [(eq? q 'false) (const false)]
+ [(eq? q 'null) (null-expr)]
+ [(string? q) (const q)]
+ [(symbol? q) (var-expr q)]
+ [(and (list? q) (eq? (length q) 2) (eq? (first q) 'null?))
+ (null?-expr (parse (second q)))]
+ [(and (list? q) (eq? (length q) 3) (eq? (first q) 'cons))
+ (cons-expr (parse (second q))
+ (parse (third q)))]
+ [(and (list? q) (eq? (length q) 2) (eq? (first q) 'car))
+ (car-expr (parse (second q)))]
+ [(and (list? q) (eq? (length q) 2) (eq? (first q) 'cdr))
+ (cdr-expr (parse (second q)))]
+ [(and (list? q) (eq? (length q) 3) (eq? (first q) 'let))
+ (let-expr (first (second q))
+ (parse (second (second q)))
+ (parse (third q)))]
+ [(and (list? q) (eq? (length q) 3) (eq? (first q) 'letrec))
+ (letrec-expr (first (second q))
+ (parse (second (second q)))
+ (parse (third q)))]
+ [(and (list? q) (eq? (length q) 4) (eq? (first q) 'if))
+ (if-expr (parse (second q))
+ (parse (third q))
+ (parse (fourth q)))]
+ [(and (list? q) (eq? (length q) 3) (eq? (first q) 'lambda))
+ (parse-lam (second q) (third q))]
+ [(and (list? q) (pair? q) (not (op->proc (car q))))
+ (parse-app q)]
+ [(and (list? q) (eq? (length q) 3) (symbol? (first q)))
+ (binop (first q)
+ (parse (second q))
+ (parse (third q)))]))
+
+(define (parse-app q)
+ (define (parse-app-accum q acc)
+ (cond [(= 1 (length q)) (app acc (parse (car q)))]
+ [else (parse-app-accum (cdr q) (app acc (parse (car q))))]))
+ (parse-app-accum (cdr q) (parse (car q))))
+
+(define (parse-lam pat e)
+ (cond [(= 1 (length pat))
+ (lam (car pat) (parse e))]
+ [else
+ (lam (car pat) (parse-lam (cdr pat) e))]))
+
+; ---------- ;
+; Srodowiska ;
+; ---------- ;
+
+(struct blackhole () #:transparent)
+(struct environ (xs) #:transparent)
+
+(define env-empty (environ null))
+(define (env-add x v env)
+ (environ (cons (mcons x v) (environ-xs env))))
+(define (env-lookup x env)
+ (define (assoc-lookup xs)
+ (cond [(null? xs) (error "Unknown identifier" x)]
+ [(eq? x (mcar (car xs)))
+ (match (mcdr (car xs))
+ [(blackhole) (error "Stuck forever in a black hole!")]
+ [x x])]
+ [else (assoc-lookup (cdr xs))]))
+ (assoc-lookup (environ-xs env)))
+(define (env-update! x v xs)
+ (define (assoc-update! xs)
+ (cond [(null? xs) (error "Unknown identifier" x)]
+ [(eq? x (mcar (car xs))) (set-mcdr! (car xs) v)]
+ [else (env-update! x v (cdr xs))]))
+ (assoc-update! (environ-xs xs)))
+(define (env-update x v xs) ; <---------------------------------- !!!
+ (define (assoc-update xs)
+ (cond [(null? xs) (list (mcons x v))]
+ [(eq? x (mcar (car xs))) (cons (mcons x v) (cdr xs))]
+ [else (cons (car xs) (assoc-update (cdr xs)))]))
+ (environ (assoc-update (environ-xs xs))))
+
+; --------- ;
+; Ewaluacja ;
+; --------- ;
+
+(struct clo (id e env) #:transparent)
+(struct let-var (v) #:transparent)
+
+(define (value? v)
+ (or (number? v)
+ (boolean? v)
+ (string? v)
+ (and (pair? v) (value? (car v)) (value? (cdr v)))
+ (null? v)
+ (clo? v)
+ (blackhole? v)))
+
+(define (op->proc op)
+ (match op ['+ +] ['- -] ['* *] ['/ /] ['% modulo]
+ ['= =] ['> >] ['>= >=] ['< <] ['<= <=]
+ ['and (lambda (x y) (and x y))]
+ ['or (lambda (x y) (or x y))]
+ ['eq? eq?]
+ [_ false]))
+
+(define (eval-env e env)
+ (match e
+ [(const n) n]
+ [(binop op l r) ((op->proc op) (eval-env l env)
+ (eval-env r env))]
+ [(let-expr x e1 e2)
+ (eval-env e2 (env-add x (let-var (eval-env e1 env)) env))]
+ [(letrec-expr x e1 e2)
+ (let* ([new-env (env-add x (blackhole) env)]
+ [v (eval-env e1 new-env)])
+ (begin
+ (env-update! x v new-env)
+ (eval-env e2 new-env)))]
+ [(var-expr x) (let ((f (env-lookup x env)))
+ (if (let-var? f) (let-var-v f) f))]
+ [(if-expr eb et ef) (if (eval-env eb env)
+ (eval-env et env)
+ (eval-env ef env))]
+ [(cons-expr e1 e2) (cons (eval-env e1 env)
+ (eval-env e2 env))]
+ [(car-expr e) (car (eval-env e env))]
+ [(cdr-expr e) (cdr (eval-env e env))]
+ [(null-expr) null]
+ [(null?-expr e) (null? (eval-env e env))]
+ [(lam x e) (clo x e env)]
+ [(app f e)
+ (let ([vf (eval-env f env)]
+ [ve (eval-env e env)])
+ (match vf [(clo x body fun-env)
+ (eval-env body (env-add x ve (merge-let-vars env fun-env)))]))]))
+
+(define (merge-let-vars env1 env2)
+ (define (iter xs env)
+ (if (null? xs)
+ env
+ (let ((cur-var (car xs)))
+ (if (let-var? (mcdr cur-var))
+ (iter (cdr xs) (env-add (mcar cur-var) (mcdr cur-var) env))
+ (iter (cdr xs) env)))))
+ (iter (reverse (environ-xs env2)) env1))
+
+(define (eval e) (eval-env e env-empty))
+
+; ---------------------------------------------------------------- !!!
+
+(struct skip () #:transparent)
+(struct assign (x e) #:transparent)
+(struct if-cmd (eb ct cf) #:transparent)
+(struct while (eb cb) #:transparent)
+(struct comp (c1 c2) #:transparent)
+
+(define (cmd? c)
+ (match c
+ [(skip) true]
+ [(assign x e) (and (symbol? x) (expr? e))]
+ [(if-cmd eb ct cf) (and (expr? eb) (cmd? ct) (cmd? cf))]
+ [(while eb ct) (and (expr? eb) (cmd? ct))]
+ [else false]))
+
+(define (parse-while q)
+ (cond
+ [(eq? q 'skip) (skip)]
+ [(null? q) (skip)]
+ [(and (list? q) (= (length q) 3) (eq? (second q) ':=))
+ (assign (first q)
+ (parse (third q)))]
+ [(and (list? q) (= (length q) 4) (eq? (car q) 'if))
+ (if-cmd (parse (second q))
+ (parse-while (third q))
+ (parse-while (fourth q)))]
+ [(and (list? q) (= (length q) 3) (eq? (car q) 'while))
+ (while (parse (second q))
+ (parse-while (third q)))]
+ [(and (list? q) (= (length q) 2))
+ (comp (parse-while (first q))
+ (parse-while (second q)))]
+ [(and (list? q) (> (length q) 2))
+ (comp (parse-while (first q))
+ (parse-while (cdr q)))]
+ [else (error "while parse error")]))
+
+(define (eval-while e env)
+ (match e
+ [(skip) env]
+ [(assign x e)
+ (env-update x (eval-env e env) env)]
+ [(if-cmd eb ct cf)
+ (if (eval-env eb env)
+ (eval-while ct env)
+ (eval-while cf env))]
+ [(while eb cb)
+ (if (eval-env eb env)
+ (eval-while e (eval-while cb env))
+ env)]
+ [(comp c1 c2) (eval-while c2 (eval-while c1 env))]))
+
+; zakladamy, ze program startuje z pamiecia w ktorej
+; aktwna jest zmienna t
+(define WHILE_FACT
+ '{(i := 1)
+ (while (> t 0)
+ {(i := (* i t))
+ (t := (- t 1))})})
+
+(define (fact n)
+ (let* ([init-env (env-add 't n env-empty)]
+ [final-env
+ (eval-while (parse-while WHILE_FACT) init-env)])
+ (env-lookup 'i final-env)))
+
+(define prog1 '{(x := 5)
+ (f := (let [x 50] (lambda (y) (+ x y))))
+ (x := 10)
+ (z := (f 0))})
\ No newline at end of file |