Re: [racket-users] Confused about syntax properties

[Dupéron Georges]

PS: a nice example to try in the macro stepper, to see the evaluation order:

#lang racket
(define-syntax (foo stx) #'1)
(define-syntax (bar stx) #'foo)

(let ()
  bar
  (let ()
bar
(let ()
  bar
  bar)
(#%expression bar)
bar)
  (+ bar bar)
  bar)

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Re: [racket-users] Confused about syntax properties

[Dupéron Georges]

Le lundi 30 janvier 2017 06:25:29 UTC+1, Matias Eyzaguirre a écrit :
> Nice, thanks! I wasn’t aware of that. so macros are expanded in the order 
> that the reader reads them, not in so called evaluation order.

>From experience, the order is outside-in, each form after the preceding one 
>(except when a macro produces a begin form, in which case the contents of the 
>begin are spliced, and handled one by one). The contents of let-values forms 
>are initially skipped, and expanded after every form in the outer let has been 
>expanded enough to determine that it is not a definition. This means that 
>within the body of a let (or of a module, I think), forms are expanded until 
>the first element is not a macro anymore (e.g. a function application with 
>#%app, an expression with #%expression, or a datum), as any remaining macro 
>could potentially expand to a definition.

Add to that a few exceptions, like things lifted with 
syntax-local-lift-expression or syntax-local-lift-module-end-declaration, and 
explicit expansion with local-expand.

I wonder if there's a definitive reference in the docs about this? I'd enjoy 
reading about how the built-in forms behave, and what mechanisms may influence 
the order of expansion (#%expression, local-expand, maybe some others?).

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Re: [racket-users] implementing make in racket

[Matthias Felleisen]

(And you also want to catch all exns at that points and put them into ch. But I 
suspect you’d have known.)


> On Feb 2, 2017, at 9:11 AM, Jay McCarthy  wrote:
> 
> I would do something like:
> 
> (define ch (make-channel))
> (submit-job! jq (lambda () (define ans ...) (channel-put ch ans)))
> (channel-get ch ans)
> 
> This will synchronously wait for the job to finish. Presumably you'd
> do this when you already started up the workers and from a context
> where you have a lot of jobs running.
> 
> Jay
> 
> 
> 
> On Wed, Feb 1, 2017 at 2:21 PM, Dan Liebgold
>  wrote:
>> On Wednesday, November 30, 2016 at 10:38:05 AM UTC-8, Jay McCarthy wrote:
>>> The typed-racket code returns a value from the job, whereas this code
>>> assumes the job is fully self-contained. Perhaps job-queue should
>>> protect itself from job exceptions.
>>> 
>> 
>> BTW, how would you recommend returning a value from a job in job-queue?
>> 
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> 
> 
> 
> -- 
> Jay McCarthy
> Associate Professor
> PLT @ CS @ UMass Lowell
> http://jeapostrophe.github.io
> 
>   "Wherefore, be not weary in well-doing,
>  for ye are laying the foundation of a great work.
> And out of small things proceedeth that which is great."
>  - D 64:33
> 
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Re: [racket-users] implementing make in racket

[Jay McCarthy]

I would do something like:

(define ch (make-channel))
(submit-job! jq (lambda () (define ans ...) (channel-put ch ans)))
(channel-get ch ans)

This will synchronously wait for the job to finish. Presumably you'd
do this when you already started up the workers and from a context
where you have a lot of jobs running.

Jay



On Wed, Feb 1, 2017 at 2:21 PM, Dan Liebgold
 wrote:
> On Wednesday, November 30, 2016 at 10:38:05 AM UTC-8, Jay McCarthy wrote:
>> The typed-racket code returns a value from the job, whereas this code
>> assumes the job is fully self-contained. Perhaps job-queue should
>> protect itself from job exceptions.
>>
>
> BTW, how would you recommend returning a value from a job in job-queue?
>
> --
> 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 
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-- 
Jay McCarthy
Associate Professor
PLT @ CS @ UMass Lowell
http://jeapostrophe.github.io

   "Wherefore, be not weary in well-doing,
  for ye are laying the foundation of a great work.
And out of small things proceedeth that which is great."
  - D 64:33

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Re: [racket-users] Beginners question: implementing existing generics for existing structs

[Ronie Uliana]

Thank you, Jon and andmkent!

Jon, I understand the reason. However, I guess it's possible to fix that kind 
of problem using precedence the same way some languages do with traits and 
mixins.

:)

Anyway, thank you again!

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