I think Sam's solution is sufficient for Typed Racket because the type computation is purely static. The problem in my case is that I need a way to identify the dynamic locations of (statically identified) variables that get created during execution.
On Wed, Nov 20, 2013 at 5:34 AM, William Cushing <[email protected]>wrote: > For emina's problem, shouldn't the implementation of typed/racket have a > clue? > > > On Wed, Nov 20, 2013 at 5:19 AM, <[email protected]> wrote: > >> Send users mailing list submissions to >> [email protected] >> >> To subscribe or unsubscribe via the World Wide Web, visit >> http://lists.racket-lang.org/users/listinfo >> or, via email, send a message with subject or body 'help' to >> [email protected] >> >> You can reach the person managing the list at >> [email protected] >> >> When replying, please edit your Subject line so it is more specific >> than "Re: Contents of users digest..." >> >> [Racket Users list: >> http://lists.racket-lang.org/users ] >> >> Today's Topics: >> >> 1. Why does this tail recursive list length function fail at cdr >> l at end of list? (Bo Gus) >> 2. Re: Why does this tail recursive list length function fail at >> cdr l at end of list? (Pierpaolo Bernardi) >> 3. Re: Why does this tail recursive list length function fail at >> cdr l at end of list? (Bo Gus) >> 4. Re: Why does this tail recursive list length function fail at >> cdr l at end of list? (Daniel Prager) >> 5. Re: Why does this tail recursive list length function fail at >> cdr l at end of list? (Daniel Prager) >> 6. Re: obtaining the location of an identifier (Robby Findler) >> >> >> ---------- Forwarded message ---------- >> From: Bo Gus <[email protected]> >> To: Racket Newsgroup <[email protected]> >> Cc: >> Date: Wed, 20 Nov 2013 11:09:28 +0000 >> Subject: [racket] Why does this tail recursive list length function fail >> at cdr l at end of list? >> My tail recursive implementation of length is like this: >> >> (define (length2 l) >> (define (l-iter l count) >> (if (null? 1) count >> (l-iter (cdr l) (+ count 1)))) >> (l-iter l 0)) >> >> If I call (length2 '(1 2 3)) and step through the code in racket, count >> increments to 3 but then on the (if (null? l) count line instead of >> returning out of the function it goes onto the next line (l-iter (cdr l) (+ >> count l)))) and of course fails at cder of an empty list. >> >> Racket error message is: >> >> mcdr: contract violation >> expected: mpair? >> given: '() >> >> >> I am fairly new to scheme. What am I doing wrong? >> >> Angus >> >> >> >> ---------- Forwarded message ---------- >> From: Pierpaolo Bernardi <[email protected]> >> To: Bo Gus <[email protected]> >> Cc: Racket Newsgroup <[email protected]> >> Date: Wed, 20 Nov 2013 12:27:40 +0100 >> Subject: Re: [racket] Why does this tail recursive list length function >> fail at cdr l at end of list? >> On Wed, Nov 20, 2013 at 12:09 PM, Bo Gus <[email protected]> wrote: >> > My tail recursive implementation of length is like this: >> > >> > (define (length2 l) >> > (define (l-iter l count) >> > (if (null? 1) count >> > (l-iter (cdr l) (+ count 1)))) >> > (l-iter l 0)) >> >> > I am fairly new to scheme. What am I doing wrong? >> >> You wrote (null? 1), which is always false. Note 1 instead of l. >> >> Cheers >> >> >> >> ---------- Forwarded message ---------- >> From: Bo Gus <[email protected]> >> To: Racket Newsgroup <[email protected]> >> Cc: >> Date: Wed, 20 Nov 2013 11:33:18 +0000 >> Subject: Re: [racket] Why does this tail recursive list length function >> fail at cdr l at end of list? >> I noticed that just after posting. >> >> I changed to: >> (define (length2 lst) >> (define (l-iter l count) >> (if (null? l) count >> (l-iter (cdr l) (+ count 1)))) >> (l-iter lst 0)) >> >> Must get better at spotting obvious mistakes... >> >> >> On 20 November 2013 11:27, Pierpaolo Bernardi <[email protected]>wrote: >> >>> On Wed, Nov 20, 2013 at 12:09 PM, Bo Gus <[email protected]> wrote: >>> > My tail recursive implementation of length is like this: >>> > >>> > (define (length2 l) >>> > (define (l-iter l count) >>> > (if (null? 1) count >>> > (l-iter (cdr l) (+ count 1)))) >>> > (l-iter l 0)) >>> >>> > I am fairly new to scheme. What am I doing wrong? >>> >>> You wrote (null? 1), which is always false. Note 1 instead of l. >>> >>> Cheers >>> >> >> >> >> ---------- Forwarded message ---------- >> From: Daniel Prager <[email protected]> >> To: Bo Gus <[email protected]>, Racket Users <[email protected]> >> Cc: >> Date: Wed, 20 Nov 2013 22:52:17 +1100 >> Subject: Re: [racket] Why does this tail recursive list length function >> fail at cdr l at end of list? >> Replace the expression (null? 1) with (null? l). You appear to have typed >> 1 (one) where you meant l (ell). >> As a general rule-of-thumb a name such as lst or a-list will reduce the >> risk of this kind of error. >> >> Dan >> >> >> ---------- Forwarded message ---------- >> From: Daniel Prager <[email protected]> >> To: Bo Gus <[email protected]>, Racket Users <[email protected]> >> Cc: >> Date: Wed, 20 Nov 2013 22:56:25 +1100 >> Subject: Re: [racket] Why does this tail recursive list length function >> fail at cdr l at end of list? >> Oops - dup. >> >> Didn't see Pierpaolo's reply. >> >> Dan >> >> >> On Wed, Nov 20, 2013 at 10:52 PM, Daniel Prager < >> [email protected]> wrote: >> >>> Replace the expression (null? 1) with (null? l). You appear to have >>> typed 1 (one) where you meant l (ell). >>> As a general rule-of-thumb a name such as lst or a-list will reduce the >>> risk of this kind of error. >>> >>> Dan >>> >> >> >> >> -- >> *Daniel Prager* >> Agile/Lean Coaching, Software Development and Leadership >> Twitter: @agilejitsu <https://twitter.com/agilejitsu> >> Blog: agile-jitsu.blogspot.com >> >> >> ---------- Forwarded message ---------- >> From: Robby Findler <[email protected]> >> To: Emina Torlak <[email protected]> >> Cc: users <[email protected]>, Sam Tobin-Hochstadt < >> [email protected]> >> Date: Wed, 20 Nov 2013 07:19:35 -0600 >> Subject: Re: [racket] obtaining the location of an identifier >> I didn't try it, but you it might work to use local-expand and then find >> all the binding forms and then rewrite them to use boxes (or some other >> source of uniqueness you might have around). >> >> Robby >> >> >> On Wed, Nov 20, 2013 at 12:53 AM, Emina Torlak >> <[email protected]>wrote: >> >>> This is how my solution currently works, but unfortunately, it's not >>> quite right. Here is a small example that demonstrates why, assuming the >>> implementation based on free-id-table: >>> >>> (define (cell init) >>> (let ([x init]) >>> (case-lambda >>> [() x] >>> [(v) (set! x v)]))) >>> >>> (define foo (cell 0)) >>> (define bar (cell 1)) >>> >>> > (foo 2) >>> > (bar 3) >>> > (foo) >>> 2 >>> > (bar) >>> 3 >>> > (dict->list global) >>> '((.#<syntax:18:17 x> . 3)) >>> >>> In the above scenario, I need the global map to contain two bindings: >>> one for the location of 'foo.x' and the other for the location of 'bar.x.' >>> >>> >>> Emina >>> >>> >>> >>> On Tue, Nov 19, 2013 at 10:31 PM, Sam Tobin-Hochstadt < >>> [email protected]> wrote: >>> >>>> I think that just identifiers and `free-id-table`s should work here. >>>> Here's your example: >>>> >>>> #lang racket >>>> >>>> (require syntax/id-table (only-in racket [set! #%set!])) >>>> >>>> (define global (make-free-id-table)) >>>> >>>> (define-syntax-rule (location-of id) #'id) >>>> >>>> (define-syntax-rule (set! id expr) >>>> (let ([v expr]) >>>> (dict-set! global (location-of id) v) >>>> (#%set! id v))) >>>> >>>> > (define x 1) >>>> > (set! x 2) >>>> > (set! x 3) >>>> > (for/list ([(k v) (in-dict global)]) (list k v)) >>>> '((.#<syntax:4:8 x> 3)) >>>> >>>> Also at https://gist.github.com/samth/7558673 >>>> >>>> Sam >>>> >>>> On Mon, Nov 18, 2013 at 2:43 PM, Emina Torlak <[email protected]> >>>> wrote: >>>> > I'm using Racket to implement a language for which I need to track >>>> state >>>> > updates---in particular, variable mutation using set!. For example, >>>> > consider this module definition: >>>> > >>>> > #lang racket >>>> > >>>> > (require (only-in racket [set! #%set!])) >>>> > >>>> > (define global (make-hash)) >>>> > >>>> > (define-syntax-rule (location-of id) >>>> > (#%variable-reference id)) ; doesn't quite do the right thing >>>> > >>>> > (define-syntax-rule (set! id expr) >>>> > (let ([val expr]) >>>> > (hash-set! global (location-of id) val) >>>> > (#%set! id val))) >>>> > >>>> > When I evaluate the following sequence of forms against the above >>>> > definition, I would like the global hash map to contain just one >>>> binding >>>> > that maps the location for 'x' to the value 2. With the above >>>> > implementation I get two map entries, since variable-reference >>>> doesn't quite >>>> > do what I hoped it did: >>>> > >>>> >> (define x 0) >>>> >> (set! x 1) >>>> >> (set! x 2) >>>> >> x >>>> > 2 >>>> >> global >>>> > '#hash((#<variable-reference> . 1) (#<variable-reference> . 2)) >>>> > >>>> > Is there another construct in Racket that I could use for this >>>> purpose? If >>>> > not, can something like this be implemented and how much work would it >>>> > entail? >>>> > >>>> > I have a purely macro-based solution that works for the most part, >>>> but it's >>>> > fragile and there are corner cases for which it is just wrong. So, >>>> before >>>> > trying to fix that, I was wondering if there is a nicer way to solve >>>> it by >>>> > somehow getting handles for variable locations that are comparable >>>> using eq? >>>> > or equal? >>>> > >>>> > Thanks! >>>> > >>>> > Emina >>>> > >>>> > >>>> > ____________________ >>>> > Racket Users list: >>>> > http://lists.racket-lang.org/users >>>> > >>>> >>> >>> >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >>> >>> >> >> > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > >
____________________ Racket Users list: http://lists.racket-lang.org/users
