Re: [racket-users] generalised set! in Racket

[Alexander D . Knauth]

On Jun 29, 2015, at 5:56 AM, Alexey Cherkaev  wrote:

> For example, I was thinking of defining syntax to access my implementation of 
> multidimensional arrays
> as
> 
> (define-syntax aref
>  (syntax-rules (set!)
>[(set! (aref ?a ?i ...) ?v) (array-set! ?a ?i ... ?v)]
>[(aref ?a ?i ...) (array-ref ?a ?i ...)]))
> 
> but obviously it won't work now as `set!` expects the `id` not an expression 
> (`syntax-id-rules` won't work either as `aref` is not an `id`).


#lang racket
(require srfi/17 math/array)
(define (aref a . is)
  (array-ref a (list->vector is)))
(set! (setter aref)
  (λ (a . is+v)
(match-define (list is ... v) is+v)
(array-set! a (list->vector is) v)))
(define a (mutable-array #[#[1 2] #[3 4]]))
(aref a 0 1)
(set! (aref a 0 1) 20)
(aref a 0 1)

If you wanted, you could also define your own version of set! that does what 
you want, which (I think) you would need to do if you needed aref to be a macro.


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Re: [racket-users] Using ‘except-in’ to exclude identifiers for a single phase level

[Alexis King]

Thanks for your help. I did consider the only-meta-in approach, but then I’d be 
excluding the syntax-rules export as well, which I was trying to avoid if 
possible.

> On Jun 29, 2015, at 7:39 AM, Matthew Flatt  wrote:
> 
> You're right that there's not a form that's like `except-out` but
> constrained both by name and phase. There's also not an export variant
> of `only-meta-in`, which would get your half-way there. You could
> implement a new provide expander to do that.
> 
> Otherwise, in addition to the strategy that you describe, another
> possibility is
> 
> (require (only-meta-in 0 r5rs)
>  ...)
> 
> Then you won't have any conflicts from `r5rs` and `racket/base` at
> phase 1, since there won't be any phase-1 imports from `r5rs`.

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Re: [racket-users] try a new macro expander

[Greg Hendershott]

Oops, didn't Cc list:

On Mon, Jun 29, 2015 at 12:13 PM, Greg Hendershott
 wrote:
> On Mon, Jun 29, 2015 at 7:43 AM, Matthew Flatt  wrote:
>> I'll have to update the version number, so there's now a
>>
>>racket-current-x86_64-linux.sh
>>
>> installer link.
>
> Thanks. Updated to use this:
>
> https://github.com/greghendershott/travis-racket/commit/5e4d01720497bac37e8f9e522253c9b778a64b5a

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Re: [racket-users] Naming conventions

[Norman Gray]

Greetings.

> On 2015 Jun 29, at 16:05, Philip Blair  wrote:
> 
> Perhaps, I'm wrong, but I don't believe there's an *explicit* convention;  
> however, as far as I've seen, it typically is used for function variants 
> (more specifically, I *usually* see it used to distinguish multiple functions 
> which do more or less the same thing with different input forms).
> 
> To quote Neil Van Dyke: "Pronounce the '/' as 'with' [...] Sometimes it's for 
> a variation in behavior, or composition of behaviors, sometimes it's just a 
> shorthand for the word 'with', and sometimes it's something else."
> Source: http://lists.racket-lang.org/users/archive/2011-September/048044.html

I've tended to make names consistent with the list of conventions collected in 
 (with 
'plt-scheme' -> 'racket').

These are mostly echoed in the Racket style guide at 

 (though I think that '#:' is a syntactical constraint that denotes keywords, 
and not just a naming convention).

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK

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Re: [racket-users] Naming conventions

[Philip Blair]

Perhaps, I'm wrong, but I don't believe there's an *explicit* 
convention;  however, as far as I've seen, it typically is used for 
function variants (more specifically, I *usually* see it used to 
distinguish multiple functions which do more or less the same thing with 
different input forms).


To quote Neil Van Dyke: "Pronounce the '/' as 'with' [...] Sometimes 
it's for a variation in behavior, or composition of behaviors, sometimes 
it's just a shorthand for the word 'with', and sometimes it's something 
else."
Source: 
http://lists.racket-lang.org/users/archive/2011-September/048044.html


On 6/29/2015 10:51 AM, John Carmack wrote:


Is there an explicit strategy for the use of / in function names, 
“overlay/xy”, “scale/xy” and so on?


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[racket-users] Naming conventions

[John Carmack]

Is there an explicit strategy for the use of / in function names, "overlay/xy", 
"scale/xy" and so on?



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Re: [racket-users] Using ‘except-in’ to exclude identifiers for a single phase level

[Matthew Flatt]

You're right that there's not a form that's like `except-out` but
constrained both by name and phase. There's also not an export variant
of `only-meta-in`, which would get your half-way there. You could
implement a new provide expander to do that.

Otherwise, in addition to the strategy that you describe, another
possibility is

 (require (only-meta-in 0 r5rs)
  ...)

Then you won't have any conflicts from `r5rs` and `racket/base` at
phase 1, since there won't be any phase-1 imports from `r5rs`.

At Sun, 28 Jun 2015 17:29:37 -0700, Alexis King wrote:
> I think it might be time for me to disclose what I’m actually trying to do 
> here to make it more clear. As mentioned in my original message, I’m trying 
> to 
> make a module language just like r5rs but with support for syntax-case 
> macros. 
> This was my attempt:
> 
> #lang racket/base
> 
> (require (except-in r5rs define-syntax)
>  (for-syntax (only-in racket/base
>   syntax quasisyntax unsyntax unsyntax-splicing
>   syntax-case with-syntax)
>  r5rs))
> 
> (provide (all-from-out r5rs)
>  define-syntax
>  (for-syntax (all-from-out r5rs)
>  (all-from-out racket/base)))
> 
> This doesn’t work, though, because #%top, #%datum, and #%app are already 
> provided for-syntax by r5rs. I can do (except-in r5rs #%top #%datum #%app 
> define-syntax), but then those identifiers aren’t defined in phase 0, which 
> obviously causes problems.
> 
> While writing this email, I realized I can additionally add (only-meta-in 0 
> (only-in r5rs #%top #%datum #%app)), which seems to solve the problem. It’s a 
> bit of a roundabout solution, though.
> 
> > On Jun 28, 2015, at 15:07, Benjamin Greenman  wrote:
> > 
> > Oops. Then I'd want to change the all-from-outs to something more specific, 
> or (preferably) change b to only provide some-fn at one level and make the 
> requiring module be more specific.
> 
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Re: [racket-users] try a new macro expander

[Matthew Flatt]

Thanks! I've pushed repairs for these problems, mreged recent changes
from the main development branches, and updated the snapshot here:

 http://www.cs.utah.edu/~mflatt/tmp/scope-snapshot/

At Thu, 25 Jun 2015 13:56:04 -0400, "Alexander D. Knauth" wrote:
> Another weird error:
> #lang racket/base
> (require racket/stxparam (for-syntax racket/base))
> (define-syntax-parameter add (make-rename-transformer #'+))
> (define-syntax add1 (make-rename-transformer #'add))
> add1
> 
> ;add1: identifier's binding is ambiguous
> ;  context.:
> ;  matching binding.:
> ;  matching binding.:
> ;  => add context.:
> ;  => add matching binding.:
> ;  matching binding.: in: add1
> 
> I found this because of this Travis CI build failure:
> https://travis-ci.org/AlexKnauth/infix-macro/jobs/68245124#L164
> 
> On Jun 25, 2015, at 12:31 AM, Matthew Flatt  wrote:
> 
> > Yes, I overlooked `splicing-local`, and I'll repair it. Thanks for the
> > report!
> > 
> > At Wed, 24 Jun 2015 20:27:39 -0400, "Alexander D. Knauth" wrote:
> >> I’ve just found something that I expected to work, but didn’t:
> >> 
> >> #lang racket/base
> >> (require racket/splicing (for-syntax racket/base))
> >> (splicing-local
> >>[(define x 1)]
> >>  (define-syntax outer-x (make-rename-transformer #'x)))
> >> outer-x
> >> 
> >> ;. outer-x: unbound identifier in module in: outer-x
> >> 
> >> This works in the current expander, but fails in the scope-set expander.
> >> 
> >> It does work for splicing-let and splicing-letrec though.
> >> 
> >> I found it because I rely on it in this macro here:
> >> https://github.com/AlexKnauth/my-object/blob/master/my-object/stuff.rkt#L25
> >> And Travis CI was giving me this error:
> >> https://travis-ci.org/AlexKnauth/my-object/jobs/68248192#L209
> >> 
> >> On Jun 22, 2015, at 8:25 AM, Matthew Flatt  wrote:
> >> 
> >>> At Thu, 21 May 2015 07:15:14 -0600, Matthew Flatt wrote:
>  Otherwise, be prepared for me to come back in a few
>  weeks and lobby for moving to a new macro expander.
> >>> 
> >>> Here's the proposal: let's switch on July 16. "Switch" means that I'd
> >>> merge the new macro expander to the master branch of the development
> >>> repository.
> >>> 
> >>> Thanks to those who have tried the new expander and reported back!
> >>> Meanwhile, I've expanded the write-up and filled out the formal model
> >>> (at the same URL as before).
> >> 
> >> 
> >> -- 
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[racket-users] overlapping fields in windows, DrRacket user interface (preferences, "choose language")

[Sanjeev Sharma]

windows 7;  it's most obvious in 
"preferences -> warnings"

also "choose language -> details" 


I can ivoke and reverse it from this screen:
 
Control Panel\Appearance and Personalization\Display
 -> make text and other items larger or smaller
   -> medium

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[racket-users] generalised set! in Racket

[Alexey Cherkaev]

Hi all,

Common Lisp has a very useful idiom of SETF that can set values to arbitrary 
places. For example, one can set (1 2)-th item of an array A as:

(SETF (AREF A 1 2) 20.0d0)

Scheme preferred way is to use `*-set!` procedures. However, sometimes it is 
inconvenient. For example, if I want to swap two elements in the array/vector, 
I would like to use `swap`:

(define-syntax swap
  (syntax-rules ()
((swap ?place1 ?place2 ?tmp)
 (begin
   (set! ?tmp ?place1)
   (set! ?place1 ?place2)
   (set! ?place2 ?place1)

But it will only work for vectors if `set!` can act as CL's SETF on generalised 
places, such as 

(swap (vector-ref v 5) (vector-ref v 3) tmp)

SRFI-17 contains the definition of such a `set!` and I can use it from there 
(AFAIR Racket supports it).

I was wondering if there is more Racket-way of doing this? And is there maybe a 
reason why `set!` wasn't given the same power as SETF?

For example, I was thinking of defining syntax to access my implementation of 
multidimensional arrays
as

(define-syntax aref
  (syntax-rules (set!)
[(set! (aref ?a ?i ...) ?v) (array-set! ?a ?i ... ?v)]
[(aref ?a ?i ...) (array-ref ?a ?i ...)]))

but obviously it won't work now as `set!` expects the `id` not an expression 
(`syntax-id-rules` won't work either as `aref` is not an `id`).

Regards, Alexey

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