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- #lang eopl
- ;******************************************************************************************
- ;;;;; Interpretador para lenguaje con condicionales, ligadura local, procedimientos,
- ;;;;; procedimientos recursivos, ejecución secuencial y asignación de variables
- ;; La definición BNF para las expresiones del lenguaje:
- ;;
- ;; <program> ::= <expression>
- ;; <a-program (exp)>
- ;; <expression> ::= <number>
- ;; <lit-exp (datum)>
- ;; ::= <identifier>
- ;; <var-exp (id)>
- ;; ::= <primitive> ({<expression>}*(,))
- ;; <primapp-exp (prim rands)>
- ;; ::= if <expresion> then <expresion> else <expression>
- ;; <if-exp (exp1 exp2 exp23)>
- ;; ::= let {<identifier> = <expression>}* in <expression>
- ;; <let-exp (ids rands body)>
- ;; ::= proc({<identificador>}*) <expression>
- ;; <proc-exp (ids body)>
- ;; ::= (<expression> {<expression>}*)
- ;; <app-exp proc rands>
- ;; ::= letrec {identifier ({identifier}*(,)) = <expression>}* in <expression>
- ;; <letrec-exp(proc-names idss bodies bodyletrec)>
- ;; ::= begin <expression> {; <expression>}* end
- ;; <begin-exp (exp exps)>
- ;; ::= set <identifier> = <expression>
- ;; <set-exp (id rhsexp)>
- ;; <primitive> ::= + | - | * | add1 | sub1
- ;******************************************************************************************
- ;******************************************************************************************
- ;Especificación Léxica
- (define scanner-spec-simple-interpreter
- '((white-sp
- (whitespace) skip)
- (comment
- ("%" (arbno (not #\newline))) skip)
- (identifier
- (letter (arbno (or letter digit "?"))) symbol)
- (number
- (digit (arbno digit)) number)
- (number
- ("-" digit (arbno digit)) number)))
- ;Especificación Sintáctica (gramática)
- (define grammar-simple-interpreter
- '((program (expression) a-program)
- (expression (number) lit-exp)
- (expression (identifier) var-exp)
- (expression
- (primitive "(" (separated-list expression ",")")")
- primapp-exp)
- (expression ("if" expression "then" expression "else" expression)
- if-exp)
- (expression ("let" (arbno identifier "=" expression) "in" expression)
- let-exp)
- (expression ("proc" "(" (arbno identifier) ")" expression)
- proc-exp)
- (expression ( "(" expression (arbno expression) ")")
- app-exp)
- (expression ("letrec" (arbno identifier "(" (separated-list identifier ",") ")" "=" expression) "in" expression)
- letrec-exp)
- ; características adicionales
- (expression ("begin" expression (arbno ";" expression) "end")
- begin-exp)
- (expression ("set" identifier "=" expression)
- set-exp)
- ;;;;;;
- (primitive ("+") add-prim)
- (primitive ("-") substract-prim)
- (primitive ("*") mult-prim)
- (primitive ("add1") incr-prim)
- (primitive ("sub1") decr-prim)))
- ;Tipos de datos para la sintaxis abstracta de la gramática
- ;Construidos manualmente:
- ;(define-datatype program program?
- ; (a-program
- ; (exp expression?)))
- ;
- ;(define-datatype expression expression?
- ; (lit-exp
- ; (datum number?))
- ; (var-exp
- ; (id symbol?))
- ; (primapp-exp
- ; (prim primitive?)
- ; (rands (list-of expression?)))
- ; (if-exp
- ; (test-exp expression?)
- ; (true-exp expression?)
- ; (false-exp expression?))
- ; (let-exp
- ; (ids (list-of symbol?))
- ; (rans (list-of expression?))
- ; (body expression?))
- ; (proc-exp
- ; (ids (list-of symbol?))
- ; (body expression?))
- ; (app-exp
- ; (proc expression?)
- ; (args (list-of expression?)))
- ; (letrec-exp
- ; (proc-names (list-of symbol?))
- ; (idss (list-of (list-of symbol?)))
- ; (bodies (list-of expression?))
- ; (body-letrec expression?))
- ; (begin-exp
- ; (exp expression?)
- ; (exps (list-of expression?)))
- ; (set-exp
- ; (id symbol?)
- ; (rhs expression?)))
- ;
- ;(define-datatype primitive primitive?
- ; (add-prim)
- ; (substract-prim)
- ; (mult-prim)
- ; (incr-prim)
- ; (decr-prim))
- ;Construidos automáticamente:
- (sllgen:make-define-datatypes scanner-spec-simple-interpreter grammar-simple-interpreter)
- (define show-the-datatypes
- (lambda () (sllgen:list-define-datatypes scanner-spec-simple-interpreter grammar-simple-interpreter)))
- ;*******************************************************************************************
- ;Parser, Scanner, Interfaz
- ;El FrontEnd (Análisis léxico (scanner) y sintáctico (parser) integrados)
- (define scan&parse
- (sllgen:make-string-parser scanner-spec-simple-interpreter grammar-simple-interpreter))
- ;El Analizador Léxico (Scanner)
- (define just-scan
- (sllgen:make-string-scanner scanner-spec-simple-interpreter grammar-simple-interpreter))
- ;El Interpretador (FrontEnd + Evaluación + señal para lectura )
- (define interpretador
- (sllgen:make-rep-loop "--> "
- (lambda (pgm) (eval-program pgm))
- (sllgen:make-stream-parser
- scanner-spec-simple-interpreter
- grammar-simple-interpreter)))
- ;*******************************************************************************************
- ;El Interprete
- ;eval-program: <programa> -> numero
- ; función que evalúa un programa teniendo en cuenta un ambiente dado (se inicializa dentro del programa)
- (define eval-program
- (lambda (pgm)
- (cases program pgm
- (a-program (body)
- (eval-expression body (init-env))))))
- ; Ambiente inicial
- ;(define init-env
- ; (lambda ()
- ; (extend-env
- ; '(x y z)
- ; '(4 2 5)
- ; (empty-env))))
- (define init-env
- (lambda ()
- (extend-env
- '(i v x)
- '(1 5 10)
- (empty-env))))
- ;(define init-env
- ; (lambda ()
- ; (extend-env
- ; '(x y z f)
- ; (list 4 2 5 (closure '(y) (primapp-exp (mult-prim) (cons (var-exp 'y) (cons (primapp-exp (decr-prim) (cons (var-exp 'y) ())) ())))
- ; (empty-env)))
- ; (empty-env))))
- ;eval-expression: <expression> <enviroment> -> numero
- ; evalua la expresión en el ambiente de entrada
- (define eval-expression
- (lambda (exp env)
- (cases expression exp
- (lit-exp (datum) datum)
- (var-exp (id) (apply-env env id))
- (primapp-exp (prim rands)
- (let ((args (eval-rands rands env)))
- (apply-primitive prim args)))
- (if-exp (test-exp true-exp false-exp)
- (if (true-value? (eval-expression test-exp env))
- (eval-expression true-exp env)
- (eval-expression false-exp env)))
- (let-exp (ids rands body)
- (let ((args (eval-rands rands env)))
- (eval-expression body
- (extend-env ids args env))))
- (proc-exp (ids body)
- (closure ids body env))
- (app-exp (rator rands)
- (let ((proc (eval-expression rator env))
- (args (eval-rands rands env)))
- (if (procval? proc)
- (apply-procedure proc args)
- (eopl:error 'eval-expression
- "Attempt to apply non-procedure ~s" proc))))
- (letrec-exp (proc-names idss bodies letrec-body)
- (eval-expression letrec-body
- (extend-env-recursively proc-names idss bodies env)))
- (set-exp (id rhs-exp)
- (begin
- (setref!
- (apply-env-ref env id)
- (eval-expression rhs-exp env))
- 1))
- (begin-exp (exp exps)
- (let loop ((acc (eval-expression exp env))
- (exps exps))
- (if (null? exps)
- acc
- (loop (eval-expression (car exps)
- env)
- (cdr exps))))))))
- ; funciones auxiliares para aplicar eval-expression a cada elemento de una
- ; lista de operandos (expresiones)
- (define eval-rands
- (lambda (rands env)
- (map (lambda (x) (eval-rand x env)) rands)))
- (define eval-rand
- (lambda (rand env)
- (eval-expression rand env)))
- ;apply-primitive: <primitiva> <list-of-expression> -> numero
- (define apply-primitive
- (lambda (prim args)
- (cases primitive prim
- (add-prim () (+ (car args) (cadr args)))
- (substract-prim () (- (car args) (cadr args)))
- (mult-prim () (* (car args) (cadr args)))
- (incr-prim () (+ (car args) 1))
- (decr-prim () (- (car args) 1)))))
- ;true-value?: determina si un valor dado corresponde a un valor booleano falso o verdadero
- (define true-value?
- (lambda (x)
- (not (zero? x))))
- ;*******************************************************************************************
- ;Procedimientos
- (define-datatype procval procval?
- (closure
- (ids (list-of symbol?))
- (body expression?)
- (env environment?)))
- ;apply-procedure: evalua el cuerpo de un procedimientos en el ambiente extendido correspondiente
- (define apply-procedure
- (lambda (proc args)
- (cases procval proc
- (closure (ids body env)
- (eval-expression body (extend-env ids args env))))))
- ;*******************************************************************************************
- ;Ambientes
- ;definición del tipo de dato ambiente
- (define-datatype environment environment?
- (empty-env-record)
- (extended-env-record
- (syms (list-of symbol?))
- (vec vector?)
- (env environment?)))
- (define scheme-value? (lambda (v) #t))
- ;empty-env: -> enviroment
- ;función que crea un ambiente vacío
- (define empty-env
- (lambda ()
- (empty-env-record))) ;llamado al constructor de ambiente vacío
- ;extend-env: <list-of symbols> <list-of numbers> enviroment -> enviroment
- ;función que crea un ambiente extendido
- (define extend-env
- (lambda (syms vals env)
- (extended-env-record syms (list->vector vals) env)))
- ;extend-env-recursively: <list-of symbols> <list-of <list-of symbols>> <list-of expressions> environment -> environment
- ;función que crea un ambiente extendido para procedimientos recursivos
- (define extend-env-recursively
- (lambda (proc-names idss bodies old-env)
- (let ((len (length proc-names)))
- (let ((vec (make-vector len)))
- (let ((env (extended-env-record proc-names vec old-env)))
- (for-each
- (lambda (pos ids body)
- (vector-set! vec pos (closure ids body env)))
- (iota len) idss bodies)
- env)))))
- ;iota: number -> list
- ;función que retorna una lista de los números desde 0 hasta end
- (define iota
- (lambda (end)
- (let loop ((next 0))
- (if (>= next end) '()
- (cons next (loop (+ 1 next)))))))
- ;(define iota
- ; (lambda (end)
- ; (iota-aux 0 end)))
- ;
- ;(define iota-aux
- ; (lambda (ini fin)
- ; (if (>= ini fin)
- ; ()
- ; (cons ini (iota-aux (+ 1 ini) fin)))))
- ;función que busca un símbolo en un ambiente
- (define apply-env
- (lambda (env sym)
- (deref (apply-env-ref env sym))))
- (define apply-env-ref
- (lambda (env sym)
- (cases environment env
- (empty-env-record ()
- (eopl:error 'apply-env-ref "No binding for ~s" sym))
- (extended-env-record (syms vals env)
- (let ((pos (rib-find-position sym syms)))
- (if (number? pos)
- (a-ref pos vals)
- (apply-env-ref env sym)))))))
- ;*******************************************************************************************
- ;Referencias
- (define-datatype reference reference?
- (a-ref (position integer?)
- (vec vector?)))
- (define deref
- (lambda (ref)
- (primitive-deref ref)))
- (define primitive-deref
- (lambda (ref)
- (cases reference ref
- (a-ref (pos vec)
- (vector-ref vec pos)))))
- (define setref!
- (lambda (ref val)
- (primitive-setref! ref val)))
- (define primitive-setref!
- (lambda (ref val)
- (cases reference ref
- (a-ref (pos vec)
- (vector-set! vec pos val)))))
- ;****************************************************************************************
- ;Funciones Auxiliares
- ; funciones auxiliares para encontrar la posición de un símbolo
- ; en la lista de símbolos de un ambiente
- (define rib-find-position
- (lambda (sym los)
- (list-find-position sym los)))
- (define list-find-position
- (lambda (sym los)
- (list-index (lambda (sym1) (eqv? sym1 sym)) los)))
- (define list-index
- (lambda (pred ls)
- (cond
- ((null? ls) #f)
- ((pred (car ls)) 0)
- (else (let ((list-index-r (list-index pred (cdr ls))))
- (if (number? list-index-r)
- (+ list-index-r 1)
- #f))))))
- ;******************************************************************************************
- ;Pruebas
- (show-the-datatypes)
- just-scan
- scan&parse
- (just-scan "add1(x)")
- (just-scan "add1( x )%cccc")
- (just-scan "add1( +(5, x) )%cccc")
- (just-scan "add1( +(5, %ccccc x) ")
- (scan&parse "add1(x)") ;#(struct:a-program #(struct:primapp-exp #(struct:incr-prim) (#(struct:var-exp x))))
- (scan&parse "add1( x )%cccc")
- (scan&parse "add1( +(5, x) )%cccc") ;#(struct:a-program #(struct:primapp-exp #(struct:incr-prim) (#(struct:primapp-exp #(struct:add-prim) (#(struct:lit-exp 5) #(struct:var-exp x))))))
- (scan&parse "add1( +(5, %cccc
- x)) ")
- (scan&parse "if -(x,4) then +(y,11) else *(y,10)") ;#(struct:a-program #(struct:if-exp #(struct:primapp-exp #(struct:substract-prim) (#(struct:var-exp x) #(struct:lit-exp 4)))
- ;#(struct:primapp-exp #(struct:add-prim) (#(struct:var-exp y) #(struct:lit-exp 11)))
- ;#(struct:primapp-exp #(struct:mult-prim) (#(struct:var-exp y) #(struct:lit-exp 10)))))
- (scan&parse "let
- x = -(y,1)
- in
- let
- x = +(x,2)
- in
- add1(x)") ;#(struct:a-program #(struct:let-exp (x) (#(struct:primapp-exp #(struct:substract-prim) (#(struct:var-exp y) #(struct:lit-exp 1))))
- ;#(struct:let-exp (x) (#(struct:primapp-exp #(struct:add-prim) (#(struct:var-exp x) #(struct:lit-exp 2))))
- ;#(struct:primapp-exp #(struct:incr-prim) (#(struct:var-exp x))))))
- (define caso1 (primapp-exp (incr-prim) (list (lit-exp 5))))
- (define exp-numero (lit-exp 8))
- (define exp-ident (var-exp 'c))
- (define exp-app (primapp-exp (add-prim) (list exp-numero exp-ident)))
- (define programa (a-program exp-app))
- (define una-expresion-dificil (primapp-exp (mult-prim)
- (list (primapp-exp (incr-prim)
- (list (var-exp 'v)
- (var-exp 'y)))
- (var-exp 'x)
- (lit-exp 200))))
- (define un-programa-dificil
- (a-program una-expresion-dificil))
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