[No scan&parse]Any easy way to testing the code in page 72 ?

[Li Weijian]

Hey, guys

I want to testing the code in page 72 in DrRacket, but I can't find the definition of scan&parse function before page 72.

After download the EOPL3's source code, I found scan&parse defined in chapter3\let-lang\lang.scm.

I tried to require the lang.scm in my code, but it seems that some code in lang.scm conflict with my testing code. 

There's a 'program' in lang.scm:

(define the-grammar

    '((program (expression) a-program)

...

But there's another similar definition in page 69:

(define-datatype program program?

  (a-program

    (exp1 expression?)))

I think I can solve this problem by spending a lot of time on modify and merge these files, but I don't think that's a good way to lean EOPL.

So I was wondering is there any easy way to debug the code in page 72?

Any help would be appreciated:)

My testing code was:

#lang eopl

(define-datatype program program?

  (a-program

   (exp1 expression?)))

(define-datatype expression expression?

  (const-exp

   (num number?))

  (diff-exp

   (exp1 expression?)

   (exp2 expression?))

  (zero?-exp

   (exp1 expression?))

  (if-exp

   (exp1 expression?)

   (exp2 expression?)

   (exp3 expression?))

  (var-exp

   (var identifier?))

  (let-exp

   (var identifier?)

   (exp1 expression?)

   (body expression?)))

(define-datatype expval expval?

  (num-val

   (num number?))

  (bool-val

   (bool boolean?)))

(define empty-env

  (lambda ()

    '()))

(define extend-env

  (lambda (var val env)

    (list var val env)))

(define apply-env

  (lambda (env search-var)

    (cond

      ((null? env) (report-no-binding-found search-var))

      ((eqv? (car env) search-var) (cadr env)) 

      (else

       (apply-env (caddr env) search-var)))))

(define report-no-binding-found

  (lambda (search-var)

    (eopl:error 'apply-env "No binding for ~s" search-var)))

(define identifier? symbol?)

(define init-env

  (lambda ()

    (extend-env

     'i (num-val 1)

     (extend-env

      'v (num-val 5)

      (extend-env

       'x (num-val 10)

       (empty-env))))))

(define expval->num

  (lambda (val)

    (cases expval val

      (num-val (num) num)

      (else (eopl:error 'expval->num "expval num extractor error:~s" val)))))

(define expval->bool

  (lambda (val)

    (cases expval val

      (bool-val (bool) bool)

      (else (eopl:error 'expval->bool "expval bool extractor error:~s" val)))))

(define run

  (lambda (string)

    (value-of-program (scan&parse string))))

(define value-of-program

  (lambda (pgm)

    (cases program pgm

      (a-program (exp1)

                 (value-of exp1 (init-env))))))

(define value-of

  (lambda (exp env)

    (cases expression exp

      (const-exp (num) (num-val num))

      (var-exp (var) (apply-env env var))

      (diff-exp (exp1 exp2)

                (let ((val1 (value-of exp1 env))

                      (val2 (value-of exp2 env)))

                  (let ((num1 (expval->num val1))

                        (num2 (expval->num val2)))

                    (num-val

                     (- num1 num2)))))

      (zero?-exp (exp1)

                 (let ((val1 (value-of exp1 env)))

                   (let ((num1 (expval->num val1)))

                     (if (zero? num1)

                         (bool-val #t)

                         (bool-val #f)))))

      (if-exp (exp1 exp2 exp3)

              (let ((val1 (value-of exp1 env)))

                (if (expval->bool val1)

                    (value-of exp2 env)

                    (value-of exp3 env))))

      (let-exp (var exp1 body)

               (let ((val1 (value-of exp1 env)))

                 (value-of body

                           (extend-env var val1 env)))))))

[Mitchell Wand]

This code uses the sllgen package. At eopl3.com, download the whole code base (allcode.zip), and look in chapter3/let-lang .  You will see that scan&parse is defined in lang.scm .

Does that help?

--Mitch

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[Li Weijian]

Nope:(

I had test the code with lang.scm, but conflicted with the code I wrote.

Read the detail I just posted:)

在 2013年7月19日星期五UTC+8上午3时59分20秒，Mitch写道：

[Mitchell Wand]

Dear Li,

Have you solved this problem yet?

--Mitch

[Luca]

Hi, it's very easy to test every program in the book.
That's how I do it:
1 - make sure you have this at the top of you definitions
#lang eopl

2 - Add the following:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;Sacanner and parser

(define scanner-spec-1
  '((white-sp (whitespace) skip)
    (comment ("%" (arbno (not #\newline))) skip)
    (identifier (letter (arbno (or letter digit))) symbol)
    (number (digit (arbno digit)) number)))

(define grammar-1
  '(
    (program   
     (expression)
     a-program)
    (expression
     (number)
     const-exp)
    (expression
     ("-(" expression "," expression ")")
     diff-exp)
    (expression
     ("zero?(" expression ")")
     zero?-exp)
    (expression
     ("if" expression "then" expression "else" expression)
     if-exp)
    (expression
     (identifier)
     var-exp)
    (expression
     ("let" identifier "=" expression "in" expression)
     let-exp)
    (expression
     ("proc" "(" identifier ")" expression)
     proc-exp)
    (expression
     ("(" expression expression")")
     call-exp)))

(sllgen:make-define-datatypes scanner-spec-1 grammar-1)

(define list-the-datatypes
  (lambda ()
    (sllgen:list-define-datatypes scanner-spec-1 grammar-1)))

(define just-scan
  (sllgen:make-string-scanner scanner-spec-1 grammar-1))

(define scan&parse
  (sllgen:make-string-parser scanner-spec-1 grammar-1))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

This code is int the appendix at the end of the book, you have to try and figure out these things on your own while using the book.
Luca

[Li Weijian]

Not yet:(

I have downloaded the source code from the website, I can understand the code of the chapter 3 in it.

It''s different from the code from the text book, there're no define-datatype program and define-datatype expression in it, it uses define the-grammar instead.

I think there should be some black magic in it, so I try to run the source code top.scm in racket, unfortunately, failed again:

`data-structures.scm:5:11: all-defined: not a provide sub-form in: (all-defined)`

I can't run the code typed by myself which was copied from the text book, and can't run the code downloaded from the website either, feel like I'm stuck here...
在 2013年7月24日星期三UTC+8下午7时38分56秒，Mitch写道：

[Mitchell Wand]

Hmm, this appears to be an issue with recent versions of Racket.

To run the code in Racket 5.3.5, change all occurrences of (all-defined) to (all-defined-out).

Sorry about that.

I am hoping to have this fixed in Racket 5.3.6 (to be released in August 2013).

--Mitch