RE: [racket-users] Racket-ese for Scheme `define-record-type' protocol?

[Matthew Flatt]

The `#:guard` option doesn't let you change the arity of the
constructor, so I don't think that's what Eric wants.

The separate `make-racr-specification` function is how I would write
it, including using `make-` as a prefix.

At Thu, 29 Dec 2016 10:53:49 +0100, "Jos Koot" wrote:
> Doesn't (struct ... #:guard guard-proc ...) not do what you want?
> See the doc on struct.
> Jos
> 
> -Original Message-
> From: racket-users@googlegroups.com [mailto:racket-users@googlegroups.com] On 
> Behalf Of Eric Eide
> Sent: jueves, 29 de diciembre de 2016 2:55
> To: Racket Users
> Subject: [racket-users] Racket-ese for Scheme `define-record-type' protocol?
> 
> Hi!  I'm translating a R6RS Scheme program to Racket, and I have a question
> about the best "Racket-ese" translation for Scheme's `define-record-type'.
> 
> Consider the following R6RS definition:
> 
> -
>  (define-record-type racr-specification
>(fields (mutable specification-phase) rules-table (mutable start-symbol))
>(opaque #t)(sealed #t)
>(protocol
> (lambda (new)
>   (lambda ()
> (new 1 (make-eq-hashtable 50) racr-nil)
> -
> 
> What is the Racket translation of the protocol specification?  Reading the
> online Racket docs, I don't see how to specify a different (and fresh per
> instance) value for every field within Racket's `struct` form.  (#:auto and
> #:auto-value are not what I want; I need different values, and fresh values,
> for every created instance.)
> 
> I guess I could "cheat" by defining the "expected" constructor myself:
> 
> -
> (define (make-racr-specification)
>   (racr-specification 1 (make-eq-hashtable 50) racr-nil))
> -
> 
> But this seems common enough that it would be built into `struct` in some way?
> Or maybe `struct` isn't what I want at all?
> 
> Thanks ---
> 
> Eric.
> (a Racket newbie)
> 
> -- 
> ---
> Eric Eide   . University of Utah School of 
> Computing
> http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 
> FAX

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RE: [racket-users] Racket-ese for Scheme `define-record-type' protocol?

[Jos Koot]

Doesn't (struct ... #:guard guard-proc ...) not do what you want?
See the doc on struct.
Jos

-Original Message-
From: racket-users@googlegroups.com [mailto:racket-users@googlegroups.com] On 
Behalf Of Eric Eide
Sent: jueves, 29 de diciembre de 2016 2:55
To: Racket Users
Subject: [racket-users] Racket-ese for Scheme `define-record-type' protocol?

Hi!  I'm translating a R6RS Scheme program to Racket, and I have a question
about the best "Racket-ese" translation for Scheme's `define-record-type'.

Consider the following R6RS definition:

-
 (define-record-type racr-specification
   (fields (mutable specification-phase) rules-table (mutable start-symbol))
   (opaque #t)(sealed #t)
   (protocol
(lambda (new)
  (lambda ()
(new 1 (make-eq-hashtable 50) racr-nil)
-

What is the Racket translation of the protocol specification?  Reading the
online Racket docs, I don't see how to specify a different (and fresh per
instance) value for every field within Racket's `struct` form.  (#:auto and
#:auto-value are not what I want; I need different values, and fresh values,
for every created instance.)

I guess I could "cheat" by defining the "expected" constructor myself:

-
(define (make-racr-specification)
  (racr-specification 1 (make-eq-hashtable 50) racr-nil))
-

But this seems common enough that it would be built into `struct` in some way?
Or maybe `struct` isn't what I want at all?

Thanks ---

Eric.
(a Racket newbie)

-- 
---
Eric Eide   . University of Utah School of Computing
http://www.cs.utah.edu/~eeide/ . +1 (801) 585-5512 voice, +1 (801) 581-5843 FAX

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