Re: evaluater problem

On Jul 22, 6:50=A0am, leppie <xacc....@[EMAIL PROTECTED]
> wrote:
> On Jul 22, 11:50=A0am, fooor...@[EMAIL PROTECTED]
 wrote:
>
>
>
>
>
> > I have to Write a procedure (rename exp) which renames all repeated
> > declarations
> > (parameters) in nested scopes. Modify =93eval-substitution.scm=94.
> >
-----------------------------------------------------------------------=
----=AD----------
> > eval-substitution.scm=94.
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ evaluator core
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;;; Pre-conditions: The given expression is legal according to the
> > concrete syntax.
> > ;;; Inner 'define' expressions are not legal.
> > ;;; Evaluator does not sup****t inner recursive procedures.
> > (define (eval exp)
> > =A0 (cond ((atomic? exp) (eval-atomic exp))
> > =A0 =A0 =A0 =A0 ((special-form? exp) (eval-special-form exp))
> > =A0 =A0 =A0 =A0 ((derived? exp) (eval-derived exp))
> > =A0 =A0 =A0 =A0 (else (apply-procedure (eval (operator exp))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0
=A0(list-of=
-values (operands exp))))))
>
> > ;~~~~~~~~~~~~~~~~~~~~ atomic ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > (define (atomic? exp)
> > =A0 (or (number? exp) (boolean? exp) (variable? exp)))
>
> > (define (eval-atomic exp)
> > =A0 (cond ((number? exp) exp)
> > =A0 =A0 =A0 =A0 ((boolean? exp) exp)
> > =A0 =A0 =A0 =A0 ((variable? exp) (lookup-variable-value exp))))
>
> > ;~~~~~~~~~~~~~~~~~~~ special form ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> > (define (special-form? exp)
> > =A0 (or (quoted? exp) (lambda? exp) (cond? exp) (definition? exp) (or?
> > exp)))
>
> > (define (eval-special-form exp)
> > =A0 (cond ((quoted? exp) (text-of-quotation exp))
> > =A0 =A0 =A0 =A0 ((lambda? exp) exp)
> > =A0 =A0 =A0 =A0 ((cond? exp) (eval-cond exp))
> > =A0 =A0 =A0 =A0 ((definition? exp) (eval-definition exp))
> > =A0 =A0 =A0 =A0 ((or? exp) (eval-or exp))))
>
> > (define (eval-cond exp)
> > =A0 (let ((clauses =A0(cond-clauses exp)))
> > =A0 =A0 (cond ((null? clauses) 'unspecified)
> > =A0 =A0 =A0 =A0 =A0 ((or (and (cond-last-clause? clauses) (eq?
(cond-pr=
edicate
> > (cond-first-clause clauses)) 'else))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0(eval (cond-predicate
(cond-first-clause=
 clauses))))
> > =A0 =A0 =A0 =A0 =A0 =A0(eval-sequence (cond-actions (cond-first-clause
=
(cond-
> > clauses exp)))))
> > =A0 =A0 =A0 =A0 =A0 (else (eval-cond (make-cond (cond-rest-clauses
(con=
d-clauses
> > exp))))))))
>
> > ;;; Purpose: Handle define expression. Bind a variable to a value in
> > the global environment.
> > (define (eval-definition exp)
> > =A0 (add-binding-to-environment (definition-variable exp) (eval
> > (definition-value exp)))
> > =A0 'ok)
>
> > (define (eval-or exp)
> > =A0 (if (null? (or-expressions exp))
> > =A0 =A0 =A0 #f
> > =A0 =A0 =A0 (let ((or-first-result (eval (or-first-expression exp))))
> > =A0 =A0 =A0 =A0 (if (or (=3D (length (or-expressions exp)) 1)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 or-first-result)
> > =A0 =A0 =A0 =A0 =A0 =A0 or-first-result
> > =A0 =A0 =A0 =A0 =A0 =A0 (eval (make-or (or-rest-expression exp)))))))
>
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ derived expressions ( syntactic
> > sugars ) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > (define (derived? exp)
> > =A0 (or (if? exp) (let? exp)))
>
> > (define (eval-derived exp)
> > =A0 (cond ((if? exp) (eval (if->cond exp)))
> > =A0 =A0 =A0 =A0 ((let? exp) (eval (let->combination exp)))))
>
> > ;;;Pre-condition: (if? exp)
> > (define (if->cond exp)
> > =A0 (let ((first-predicate =A0(if-predicate exp))
> > =A0 =A0 =A0 =A0 (first-actions (list (if-consequent exp)))
> > =A0 =A0 =A0 =A0 (second-actions (list (if-alternative exp))) )
> > =A0 =A0 (let ( (first-clause (make-cond-clause first-predicate first-
> > actions))
> > =A0 =A0 =A0 =A0 =A0 =A0(second-clause (make-cond-clause 'else
second-ac=
tions)) )
> > =A0 =A0 =A0 =A0 =A0 (make-cond (list first-clause second-clause))
> > =A0 =A0 =A0 =A0 )))
>
> > ;;; Pre-conditions: (let? exp)
> > (define (let->combination exp)
> > =A0 (make-application (make-lambda (let-variables exp) (let-body exp))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (let-initial-values exp)))
>
> > ;~~~~~~~~~~~~~~~~~ application ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> > (define (apply-procedure procedure arguments)
> > =A0 (cond ((lambda? procedure)
> > =A0 =A0 =A0 =A0 =A0(eval-sequence
> > =A0 =A0 =A0 =A0 =A0 (substitute (lambda-body procedure)
(lambda-paramet=
ers
> > procedure) arguments)))
> > =A0 =A0 =A0 =A0 ((defined-proc-in-global? procedure)
> > =A0 =A0 =A0 =A0 =A0(apply-primitive-procedure procedure arguments))
> > =A0 =A0 =A0 =A0 (else
> > =A0 =A0 =A0 =A0 =A0(error
> > =A0 =A0 =A0 =A0 =A0 "eval: Illegal procedure" procedure))))
>
> > (define (eval-sequence exps)
> > =A0 (cond ((null? (cdr exps)) (eval (car exps)))
> > =A0 =A0 =A0 =A0 (else (eval (car exps))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 (eval-sequence (cdr exps)))))
>
> > (define (apply-primitive-procedure proc args)
> > =A0 (apply proc args)) ; apply in underlying Scheme
>
> > ;;; list-of-values is used in 'eval'.
> > (define (list-of-values exps)
> > =A0 (if (no-operands? exps)
> > =A0 =A0 =A0 ()
> > =A0 =A0 =A0 (cons (eval (first-operand exps))
> > =A0 =A0 =A0 =A0 =A0 =A0 (list-of-values (rest-operands exps)))))
>
> > ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;~~~~~~~~~~~~~~~~ substitute procedures ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;;; Pre-conditions: substitute is not performed on 'define' or 'let'
> > expressions
> > ;;; or expression containing such sub-expressions.
> > (define (substitute exp vars vals)
> > =A0 (letrec (( substitute-var-val
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0(lambda (exp var val)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0(cond ((or (number? exp) (quoted? exp)
(=
boolean? exp))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 exp)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0((variable? exp)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (if (and (eq? exp var))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 val ;; substitute
f=
ree occurrence of var
> > with val
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 exp))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0((lambda? exp)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (if (memq =A0var
(lambda-pa=
rameters exp))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 exp
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (make-lambda
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0
=A0(lambda-paramete=
rs exp)
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0(map (lambda
(e)=
 (substitute-var-val e var
> > val))
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0
(lambda=
-body
> > exp)))) )
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0(else ; expression is a
list=
 of expressions:
> > application, cond.
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 (map (lambda(e)
(substitute=
-var-val e var val))
> > exp)))) ))
> > =A0 =A0 (if (and (null? vars) (null? vals))
> > =A0 =A0 =A0 =A0 exp
> > =A0 =A0 =A0 =A0 (substitute
> > =A0 =A0 =A0 =A0 =A0(substitute-var-val exp (car vars) (car vals))
> > =A0 =A0 =A0 =A0 =A0(cdr vars)
> > =A0 =A0 =A0 =A0 =A0(cdr vals))
> > =A0 =A0 =A0 =A0 ) ))
>
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ global environment ADT
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~~~~=AD~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> > (define global-environment
> > =A0 (list
> > =A0 =A0; primitive procedures
> > =A0 =A0(list 'car car)
> > =A0 =A0(list 'cdr cdr)
> > =A0 =A0(list 'cons cons)
> > =A0 =A0(list 'null? null?)
> > =A0 =A0(list 'list list)
> > =A0 =A0(list 'length length)
> > =A0 =A0(list '+ +)
> > =A0 =A0(list '* *)
> > =A0 =A0(list '> >)
> > =A0 =A0(list '< <)
> > =A0 =A0(list '- -)
> > =A0 =A0(list '=3D =3D)
> > =A0 =A0(list 'expt expt)
> > =A0 =A0))
>
> > (define (lookup-variable-value var)
> > =A0 (if (assoc var global-environment)
> > =A0 =A0 =A0 (cadr (assoc var global-environment))
> > =A0 =A0 =A0 (error "variable is not defined" var )))
>
> > (define (defined-proc-in-global? proc)
> > =A0 (member proc (map cadr global-environment)))
>
> > (define (add-binding-to-environment var val)
> > =A0 (set! global-environment (cons (list var val)
global-environment)))
> >
-----------------------------------------------------------------------=
----=AD----------------------------------------
> > The procedure may have internal procedures defined using letrec. Use
> > parser
> > procedures to get and build the expressions components.
> > Use the primitive procedure gensym to give a new variable name. For
> > example,> (gensym)
> > g305
> > > (gensym)
>
> > g306
> > Here are some examples of how rename is expected to work:>(rename 3)
> > 3
> > >(rename '(quote r))
> > 2
> > >r
> > >(rename '(x 3))
> > (x 3)
> > >(rename '(lambda(x y)
>
> > (* x y)))
> > (lambda (x y) (* x y))>(rename '(lambda(x y)
>
> > (* ((lambda(y z)
> > (+ y x)) x y
> > )
> > y)))
> > (lambda (x y)
> > (* ((lambda (g423 z)
> > (+ g423 x)) x y
> > )
> > y))>(rename '(lambda(x y)
>
> > (* ((lambda(y z)
> > (+ y ((lambda (x)
> > x)
> > x)))
> > x y)
> > y)))
> > (lambda (x y)
> > (* ((lambda (g446 z)
> > (+ g446 ((lambda (g445)
> > g445)
> > x)))
> > x y)
> > y))
> > Hint: review the substitute procedure and take ideas from it. The
> > procedure
> > rename may be similar to substitute and may even call substitute.
> > The contract
> > ;;; 1. Signature: (rename exp)
> > ;;; 2. Type: Expression -> Expression
> > ;;; 3. Purpose: renames all repeated declarations (parameters) in
> > nested scopes.
> > ;;; 4. Example: above.
> > ;;; 5. Pre-conditions: exp is a legal expression.
> > ;;; 6. Post-conditions: the result is an expression with identical
> > functionality to
> > exp.
> > ;;; 7. Tests:
>
> Sorry, we cant do your homework for you...- Hide quoted text -
>
> - Show quoted text -

i just want from you a main points what to do and not to solve the
exersice!
Regards