[racket-dev] raco make cannot marshal value error

Maybe it would be good to have official support for safe 3D values.

I realized after I wrote the `images/compile-time' module that it was 
just a special case. It could be extended to handle anything 
serializable. Having to serialize values at expansion time and 
unserialize them at runtime makes 3D values pretty safe.

Neil ⊥

On 07/27/2012 05:56 AM, Matthias Felleisen wrote:
>
> I am almost sure there are additional explanations of 3d syntax and its problems between then and now.
>
> When we (re)discovered 3d syntax at IU in 1984, we thought it was better than sliced bread. So it is natural that many other people re-discover it and want to use it in Racket.
>
>
>
> On Jul 27, 2012, at 5:35 AM, Tobias Hammer wrote:
>
>> Thanks for the explanation. I think i understand now what i did wrong.
>> The 3D syntax was a good hint for further reading. I digged up a thread*
>> where you already had to explain it 10 years ago :)
>>
>> Tobias
>>
>> * http://www.cs.utah.edu/plt/mailarch/plt-scheme-2002/msg00111.html
>>
>>
>> On Thu, 26 Jul 2012 15:36:44 +0200, Matthew Flatt <mflatt at cs.utah.edu> wrote:
>>
>>> I agree that it's a bug, in a sense, that your program runs even though
>>> it cannot be compiled.
>>>
>>> This is an example of "3-D syntax": you're embedding a value (i.e., an
>>> instance of `s') that you can't write as a literal into the result of a
>>> macro expansion. I think 3-D syntax probably should not be allowed, but
>>> the macro system currently allows it.
>>>
>>> Most likely, using 3-D syntax is a bad idea. It's possible that you
>>> want to replace `#:transparent' with `#:prefab' in your example, since
>>> a prefab structure can be written as a literal. More likely, I think
>>> you want to generate an expression that constructs an `s' instead of
>>> generating an `s' instance in the macro expansion.
>>>
>>> At Thu, 26 Jul 2012 14:59:41 +0200, Tobias Hammer wrote:
>>>> Hi,
>>>>
>>>> i have the following two files, one that only requires the other and
>>>> calls a macro and the other one that defines that macro:
>>>>
>>>> === main.rkt
>>>> #lang racket
>>>>
>>>> (require "err.rkt")
>>>> (a)
>>>>
>>>> === err.rkt
>>>> #lang racket
>>>>
>>>> (begin-for-syntax
>>>>   (struct s (arg) #:transparent)
>>>>
>>>>   (define (fun arg)
>>>>     (printf "arg: ~a\n" arg)))
>>>>
>>>> (define-syntax (a stx)
>>>>    (syntax-case stx ()
>>>>      [(_)
>>>>       (with-syntax ([v #`#,(s 123)])
>>>>         #'(begin
>>>>             (begin-for-syntax
>>>>              (fun v))))]))
>>>>
>>>> (provide a)
>>>>
>>>> When executing 'racket main.rkt' directly i get the expected output
>>>> arg: #(struct:s 123)
>>>> but when i try to call 'raco make main.rkt' instead, i get this strange
>>>> error:
>>>>
>>>> arg: #(struct:s 123)
>>>> write: cannot marshal value that is embedded in compiled code
>>>>    value: (s 123)
>>>>    context...:
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:388:6
>>>>
>>>> /home_local/hamm_to/racket/racket-5.3.0.16/collects/racket/private/more-scheme.r
>>>> kt:151:2:
>>>> call-with-break-parameterization
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:188:5
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:508:26
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:501:42
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:466:0:
>>>> maybe-compile-zo
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:579:2:
>>>> do-check
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/cm.rkt:653:4
>>>>
>>>> /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/commands/make.rkt:7
>>>> 7:8:
>>>> for-loop
>>>>
>>>> /home_local/hamm_to/racket/racket-5.3.0.16/collects/compiler/commands/make.rkt:
>>>>
>>>> [running body]
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/raco/raco.rkt:
>>>> [running body]
>>>>     /home_local/hamm_to/racket/racket-5.3.0.16/collects/raco/main.rkt:
>>>> [running body]
>>>>
>>>> I think i need a little help to understand what is happening here
>>>> and what i am doing wrong. I had expected that running and compiling
>>>> works on the same set of programs.
>>>>
>>>> Thanks for any clarification.
>>>>
>>>> Tobias
>>>>
>>>>
>>>>
>>>> --
>>>> ---------------------------------------------------------
>>>> Tobias Hammer
>>>> DLR / Institute of Robotics and Mechatronics
>>>> Tel.: 08153/28-1487
>>>> Mail: tobias.hammer at dlr.de
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