Re: [racket-users] Simple macro issues

[Simon Haines]

Thanks Sorawee,

So what is 'num' inside define-syntax-rule if not a syntax object? And why 
did my earlier attempt create a macro that tried to evaluate its arguments? 
In other words, what are the steps I need to take, or the realisations I 
need to make, to work back from "a: unbound identifier in: a" to a solution 
like you provided? Thanks again.


On Monday, 9 September 2019 15:31:29 UTC+10, Sorawee Porncharoenwase wrote:
>
> This works for me:
>
> #lang racket
>
> (define (hex:char x)
>   (if (number? x)
>   x
>   (string->number (symbol->string x) 16)))
>
> (define-syntax-rule (hex num ...) (bytes (hex:char (quote num)) ...))
>
> (hex a b c 1 2 3) ; #"\n\v\f\1\2\3"
>
> It’s almost always a mistake to use a function that manipulate syntax 
> object (syntax-e, etc.) inside syntax-rules, because syntax-rules don’t 
> give you an access to the syntax object. If you do want to manipulate 
> syntax object, use syntax-cases instead. In your case, however, the 
> problem is easy enough that you don’t need to directly manipulate syntax 
> objects.
>
> On Mon, Sep 9, 2019 at 12:12 PM Simon Haines  > wrote:
>
>> I'm trying to write a macro that will turn a list of hex literals into a 
>> byte string.
>>
>> (hex a b c 1 2 3) ; #"\n\v\f\1\2\3"
>>
>> After many hours I have finally come up with this:
>>
>> #lang racket
>> (define-syntax hex
>>   (syntax-rules ()
>> [(_ num ...)
>>  (bytes
>>   (let ([e (syntax-e #'num)])
>> (if (number? e) num
>> (string->number (symbol->string e) 16))) ...)]))
>>
>> (hex a b c 1 2 3)
>>
>> Of course there are many issues with checking the parameters etc. My 
>> problem is this generates "a: unbound identifier in: a" because the 
>> arguments are evaluated? If I remove the last line it works in the REPL OK.
>>
>> I suspect this is a small matter of my phases being mixed up, or a 
>> misunderstanding of when macros can be defined and used, or just outright 
>> ignorance on my part. I couldn't find any clues in the many, many 
>> references and tutorials I have read. I want to master them but I loathe 
>> creating macros, they always make me feel like an idiot, and I hope Racket2 
>> simplifies them somehow.
>>
>> Thanks for any help sorting this one out.
>>
>> -- 
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>>  
>> 
>> .
>>
>

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Re: [racket-users] Simple macro issues

[Sorawee Porncharoenwase]

This works for me:

#lang racket

(define (hex:char x)
  (if (number? x)
  x
  (string->number (symbol->string x) 16)))

(define-syntax-rule (hex num ...) (bytes (hex:char (quote num)) ...))

(hex a b c 1 2 3) ; #"\n\v\f\1\2\3"

It’s almost always a mistake to use a function that manipulate syntax
object (syntax-e, etc.) inside syntax-rules, because syntax-rules don’t
give you an access to the syntax object. If you do want to manipulate
syntax object, use syntax-cases instead. In your case, however, the problem
is easy enough that you don’t need to directly manipulate syntax objects.

On Mon, Sep 9, 2019 at 12:12 PM Simon Haines <
simon.hai...@con-amalgamate.net> wrote:

> I'm trying to write a macro that will turn a list of hex literals into a
> byte string.
>
> (hex a b c 1 2 3) ; #"\n\v\f\1\2\3"
>
> After many hours I have finally come up with this:
>
> #lang racket
> (define-syntax hex
>   (syntax-rules ()
> [(_ num ...)
>  (bytes
>   (let ([e (syntax-e #'num)])
> (if (number? e) num
> (string->number (symbol->string e) 16))) ...)]))
>
> (hex a b c 1 2 3)
>
> Of course there are many issues with checking the parameters etc. My
> problem is this generates "a: unbound identifier in: a" because the
> arguments are evaluated? If I remove the last line it works in the REPL OK.
>
> I suspect this is a small matter of my phases being mixed up, or a
> misunderstanding of when macros can be defined and used, or just outright
> ignorance on my part. I couldn't find any clues in the many, many
> references and tutorials I have read. I want to master them but I loathe
> creating macros, they always make me feel like an idiot, and I hope Racket2
> simplifies them somehow.
>
> Thanks for any help sorting this one out.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Racket Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to racket-users+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/racket-users/6d096642-b770-4655-acc5-08b36e176554%40googlegroups.com
> 
> .
>

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[racket-users] Simple macro issues

[Simon Haines]

I'm trying to write a macro that will turn a list of hex literals into a 
byte string.

(hex a b c 1 2 3) ; #"\n\v\f\1\2\3"

After many hours I have finally come up with this:

#lang racket
(define-syntax hex
  (syntax-rules ()
[(_ num ...)
 (bytes
  (let ([e (syntax-e #'num)])
(if (number? e) num
(string->number (symbol->string e) 16))) ...)]))

(hex a b c 1 2 3)

Of course there are many issues with checking the parameters etc. My 
problem is this generates "a: unbound identifier in: a" because the 
arguments are evaluated? If I remove the last line it works in the REPL OK.

I suspect this is a small matter of my phases being mixed up, or a 
misunderstanding of when macros can be defined and used, or just outright 
ignorance on my part. I couldn't find any clues in the many, many 
references and tutorials I have read. I want to master them but I loathe 
creating macros, they always make me feel like an idiot, and I hope Racket2 
simplifies them somehow.

Thanks for any help sorting this one out.

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Re: [racket-users] Applicable sets and hashes?

[Maciek Godek]

Great, thanks!

W dniu niedziela, 8 września 2019 11:57:47 UTC+2 użytkownik ricardo.g.herdt 
napisał:
>
> Hi Maciek, 
>
> yes, it is. Take a look at rackjure: 
>
> https://docs.racket-lang.org/rackjure/index.html#(part._dict-app) 
>
> Regards, 
>
> Ricardo 
>
>
> Am 08.09.2019 11:51 schrieb Maciek Godek: 
> > Hi, 
> > is it possible to take Racket's hash tables and sets, and make them 
> > applicable (like in Clojure)? 
> > 
> > So that, for example 
> > 
> > (#hash((a . 1) (b . 2)) 'a) 
> > 
> > would be equivalent to 
> > 
> > (hash-ref #hash((a . 1) (b . 2)) 'a) 
> > 
> > and 
> > 
> > ((set 1 2 3) 1) 
> > 
> > would be equivalent to 
> > 
> > (set-member? (set 1 2 3) 1) 
> > 
> >  -- 
> >  You received this message because you are subscribed to the Google 
> > Groups "Racket Users" group. 
> >  To unsubscribe from this group and stop receiving emails from it, 
> > send an email to racket...@googlegroups.com . 
> >  To view this discussion on the web visit 
> > 
> https://groups.google.com/d/msgid/racket-users/879ae299-8f3f-4b9a-b13e-16727f347cb8%40googlegroups.com
>  
> > [1]. 
> > 
> > 
> > Links: 
> > -- 
> > [1] 
> > 
> https://groups.google.com/d/msgid/racket-users/879ae299-8f3f-4b9a-b13e-16727f347cb8%40googlegroups.com?utm_medium=email_source=footer
>  
>

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RE: [racket-users] transparency of structs?

[jos.koot]

Thanks,
make-sibling-inspector does what I want.
Jos

-Mensaje original-
De: Ben Greenman  
Enviado el: 08 September 2019 01:20
Para: jos.k...@gmail.com
CC: Racket Users 
Asunto: Re: [racket-users] transparency of structs?

I see the same results on Racket 7.0 and 6.5, so I don't think anything has 
changed.

Maybe the trouble is that (make-inspector) makes a subinspector of 
(current-inspector), which has the same value for both the main module & the 
submodules.

Switching to (make-sibling-inspector) causes (struct? an-s) to return #f


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[racket-users] On multilanguage programming

[Hendrik Boom]

I found an interesting document on the STEPS project, presenting the 
astonishing benefits of clever design and the use and improvisation of many, 
many programming languages in one project.

http://www.vpri.org/pdf/tr2012001_steps.pdf

-- hendrik

(found in a document list http://vpri.org/writings.php
which probably lists many other documents of interest)

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Re: [racket-users] Applicable sets and hashes?

[Ricardo Herdt]

Hi Maciek,

yes, it is. Take a look at rackjure:

https://docs.racket-lang.org/rackjure/index.html#(part._dict-app)

Regards,

Ricardo


Am 08.09.2019 11:51 schrieb Maciek Godek:

Hi,
is it possible to take Racket's hash tables and sets, and make them
applicable (like in Clojure)?

So that, for example

(#hash((a . 1) (b . 2)) 'a)

would be equivalent to

(hash-ref #hash((a . 1) (b . 2)) 'a)

and

((set 1 2 3) 1)

would be equivalent to

(set-member? (set 1 2 3) 1)

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[1].


Links:
--
[1]
https://groups.google.com/d/msgid/racket-users/879ae299-8f3f-4b9a-b13e-16727f347cb8%40googlegroups.com?utm_medium=email_source=footer


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[racket-users] Applicable sets and hashes?

[Maciek Godek]

Hi,
is it possible to take Racket's hash tables and sets, and make them 
applicable (like in Clojure)?

So that, for example

(#hash((a . 1) (b . 2)) 'a)

would be equivalent to

(hash-ref #hash((a . 1) (b . 2)) 'a)

and 

((set 1 2 3) 1)

would be equivalent to

(set-member? (set 1 2 3) 1)


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Re: [racket-users] [OT] Cities and GPS

[Laurent]

This DB is even better:
http://download.geonames.org/export/


On Sun, Sep 8, 2019 at 8:34 AM Laurent  wrote:

> Nice :)
>
>
> On Sat, Sep 7, 2019 at 2:00 AM Alex Harsanyi 
> wrote:
>
>> In fact, I updated the data frame package to be able to read the CSV file
>> directly, without having to process it, so the example now becomes:
>>
>> #lang racket
>> (require data-frame)
>>
>> (define df (df-read/csv "worldcities.csv" #:quoted-numbers? #t))
>>
>> (define ((is-city? name) v)
>>   (equal? (vector-ref v 0) name))
>>
>> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>>
>> ;; Produces:
>>
>> ;; '#(#("Perth" "Australia" -31.955 115.84)
>> ;;  #("Perth" "United Kingdom" 56.4003 -3.47))
>>
>> Alex.
>>
>>
>> On Saturday, September 7, 2019 at 8:13:28 AM UTC+8, Alex Harsanyi wrote:
>>>
>>>
>>> That database is simple enough to use directly, not sure if it needs a
>>> separate package:
>>>
>>> #lang racket
>>> (require data-frame)
>>>
>>> ;; The worldcities.csv file has all values quoted, so df-read/csv reads
>>> them
>>> ;; all as strings.  Convert a series to numbers.
>>> (define (->numeric df series)
>>>   (df-add-derived df series (list series) (lambda (v) (string->number (car
>>> v)
>>>
>>> (define df (df-read/csv "worldcities.csv"))
>>>
>>>   ;; Convert numeric series to numbers
>>> (for ([series '("lat" "lng" "population")])
>>>   (->numeric df series))
>>>
>>> (define ((is-city? name) v)
>>>   (equal? (vector-ref v 0) name))
>>>
>>> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>>>
>>> ;; The above call produces:
>>>
>>> ;; '#(#("Perth" "Australia" -31.955 115.84)
>>> ;;#("Perth" "United Kingdom" 56.4003 -3.47))
>>>
>>>
>>>
>>> Alex.
>>>
>>> On Friday, September 6, 2019 at 8:37:59 PM UTC+8, Laurent wrote:

 There's a small free database here too:
 https://simplemaps.com/data/world-cities

 I started writing a simple query system for it this morning (csv->rktd,
 then just list of assoc operations).

 On Fri, Sep 6, 2019 at 1:35 PM Sage Gerard 
 wrote:

> Would geonames help?
> http://www.geonames.org/
>
>
>  Original Message 
> On Sep 6, 2019, 8:28 AM, Hendrik Boom < hen...@topoi.pooq.com> wrote:
>
>
> On Thu, Sep 05, 2019 at 10:42:01PM -0700, Alex Harsanyi wrote:
> ...
> >
> > >
> > > A package containing a database of the positions of the major
> cities and
> > > countries would be nice too :)
> > >
> >
> >
> > A general facility able to resolve location names to GPS coordinates
> would
> > be a lot of work, and I don't have time for such a thing. Sorry.
>
> There must be a GPS database of cities available somewhere already.
>
> -- hendrik
>
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> 
> .
>
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>> 
>> .
>>
>

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Re: [racket-users] [OT] Cities and GPS

[Laurent]

Nice :)


On Sat, Sep 7, 2019 at 2:00 AM Alex Harsanyi  wrote:

> In fact, I updated the data frame package to be able to read the CSV file
> directly, without having to process it, so the example now becomes:
>
> #lang racket
> (require data-frame)
>
> (define df (df-read/csv "worldcities.csv" #:quoted-numbers? #t))
>
> (define ((is-city? name) v)
>   (equal? (vector-ref v 0) name))
>
> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>
> ;; Produces:
>
> ;; '#(#("Perth" "Australia" -31.955 115.84)
> ;;  #("Perth" "United Kingdom" 56.4003 -3.47))
>
> Alex.
>
>
> On Saturday, September 7, 2019 at 8:13:28 AM UTC+8, Alex Harsanyi wrote:
>>
>>
>> That database is simple enough to use directly, not sure if it needs a
>> separate package:
>>
>> #lang racket
>> (require data-frame)
>>
>> ;; The worldcities.csv file has all values quoted, so df-read/csv reads
>> them
>> ;; all as strings.  Convert a series to numbers.
>> (define (->numeric df series)
>>   (df-add-derived df series (list series) (lambda (v) (string->number (car
>> v)
>>
>> (define df (df-read/csv "worldcities.csv"))
>>
>>   ;; Convert numeric series to numbers
>> (for ([series '("lat" "lng" "population")])
>>   (->numeric df series))
>>
>> (define ((is-city? name) v)
>>   (equal? (vector-ref v 0) name))
>>
>> (df-select* df "city" "country" "lat" "lng" #:filter (is-city? "Perth"))
>>
>> ;; The above call produces:
>>
>> ;; '#(#("Perth" "Australia" -31.955 115.84)
>> ;;#("Perth" "United Kingdom" 56.4003 -3.47))
>>
>>
>>
>> Alex.
>>
>> On Friday, September 6, 2019 at 8:37:59 PM UTC+8, Laurent wrote:
>>>
>>> There's a small free database here too:
>>> https://simplemaps.com/data/world-cities
>>>
>>> I started writing a simple query system for it this morning (csv->rktd,
>>> then just list of assoc operations).
>>>
>>> On Fri, Sep 6, 2019 at 1:35 PM Sage Gerard  wrote:
>>>
 Would geonames help?
 http://www.geonames.org/


  Original Message 
 On Sep 6, 2019, 8:28 AM, Hendrik Boom < hen...@topoi.pooq.com> wrote:


 On Thu, Sep 05, 2019 at 10:42:01PM -0700, Alex Harsanyi wrote:
 ...
 >
 > >
 > > A package containing a database of the positions of the major
 cities and
 > > countries would be nice too :)
 > >
 >
 >
 > A general facility able to resolve location names to GPS coordinates
 would
 > be a lot of work, and I don't have time for such a thing. Sorry.

 There must be a GPS database of cities available somewhere already.

 -- hendrik

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