[racket-dev] Unique identifiers

Thanks, I'll look into that.  It's implemented in the C code, but it looks
like it's effectively doing a combination of generate-temporary and
syntax-local-lift-module-end-declaration.  I don't think it gives me the
option of creating two fresh identifiers with the same printed name in the
same module and have them be immediately unique via free-identifier=?, as
the binding would not have taken effect yet, so to speak.  This is one of
those cases where my life would be so much easier if I could relax any one
of the constraints I'm working under.

Carl Eastlund


On Fri, May 31, 2013 at 9:58 AM, Eric Dobson <eric.n.dobson at gmail.com>wrote:

> If you replace all of your internal definition manipulation with
> (syntax-local-lift-expression #'#f), it passes your check.rkt. You
> don't have control over the names, but I'm guessing you could look
> into the implementation and see what it is doing to generate such
> names.
>
> On Fri, May 31, 2013 at 8:32 AM, Carl Eastlund <cce at ccs.neu.edu> wrote:
> > I want a non-probabilistic guarantee of uniqueness, partly because I'd
> > rather not rely on something nondeterministic, and partly because in an
> > ideal solution, I'd like to have control over the printed names of these
> > identifiers.
> >
> > Carl Eastlund
> >
> > On Fri, May 31, 2013 at 9:27 AM, Eric Dobson <eric.n.dobson at gmail.com>
> > wrote:
> >>
> >> What does unique mean in this context? Does probabilistically unique
> >> work? If so could you form an identifier with the symbolic form
> >> "unique-id-"+UUID?
> >>
> >> On Fri, May 31, 2013 at 8:20 AM, Carl Eastlund <cce at ccs.neu.edu> wrote:
> >> > I'm having trouble creating identifiers that are unique with respect
> to
> >> > free-identifier=? and that survive marshaling to compiled code.  The
> >> > normal
> >> > source of fresh identifiers, generate-temporaries, only guarantees
> they
> >> > are
> >> > unique with respect to bound-identifier=?.  The obvious alternative,
> >> > gensym,
> >> > does not properly survive marshaling -- copies saved in different .zo
> >> > files
> >> > load as distinct identifiers.  I've tried a few alternative methods,
> >> > none
> >> > more successful than either of these.
> >> >
> >> > Below, there are a few short files that show the difficulties and can
> be
> >> > used to test other methods.  The first, fresh.rkt, contains the
> >> > procedure
> >> > used to create fresh identifiers.  The file original.rkt creates a
> fresh
> >> > identifier at compile time.  The file identical.rkt copies the
> >> > identifier
> >> > from original.rkt using quote-syntax.  The file different.rkt creates
> >> > another fresh identifier at compile time.  The file check.rkt checks
> >> > that
> >> > the identifiers from original.rkt and identical.rkt are
> >> > free-identifier=? to
> >> > each other, and that the identifiers from original.rkt and
> different.rkt
> >> > are
> >> > not free-identifier=? to each other.  To run a test, first update
> >> > fresh.rkt
> >> > to use the appropriate method for creating identifiers, then run "raco
> >> > make
> >> > check.rkt".  Some of the methods work when simply running "racket
> >> > check.rkt", but "raco make" marshals the identifiers to .zo files and
> >> > exposes more problems.
> >> >
> >> > Can anyone suggest an implementation that would work here?
> >> >
> >> > ;;;;; fresh.rkt
> >> > #lang racket
> >> > (begin-for-syntax
> >> >   (require racket/syntax)
> >> >   (define (fresh)
> >> >     ;; does not guarantee free-identifier=?
> >> >     #;(generate-temporary)
> >> >     ;; does not survive marshaling
> >> >     #;(gensym)
> >> >     ;; also does not survive marshaling
> >> >     (begin
> >> >       (define id0 (datum->syntax #false 'fresh))
> >> >       (define ctx (syntax-local-make-definition-context))
> >> >       (syntax-local-bind-syntaxes (list id0) #false ctx)
> >> >       (internal-definition-context-seal ctx)
> >> >       (internal-definition-context-apply ctx id0)))
> >> >   (provide fresh))
> >> >
> >> > ;;;;; original.rkt
> >> > #lang racket
> >> > (require "fresh.rkt")
> >> > (define-syntax (macro stx)
> >> >   (with-syntax {[name (fresh)]}
> >> >     #'(begin-for-syntax
> >> >         (define original (quote-syntax name))
> >> >         (provide original))))
> >> > (macro)
> >> >
> >> > ;;;;; identical.rkt
> >> > #lang racket
> >> > (require "original.rkt")
> >> > (define-syntax (macro stx)
> >> >   (with-syntax {[orig original]}
> >> >     #'(begin-for-syntax
> >> >         (define identical (quote-syntax orig))
> >> >         (provide identical))))
> >> > (macro)
> >> >
> >> > ;;;;; different.rkt
> >> > #lang racket
> >> > (require "fresh.rkt")
> >> > (define-syntax (macro stx)
> >> >   (with-syntax {[name (fresh)]}
> >> >     #'(begin-for-syntax
> >> >         (define different (quote-syntax name))
> >> >         (provide different))))
> >> > (macro)
> >> >
> >> > ;;;;; check.rkt
> >> > #lang racket
> >> > (require "fresh.rkt" "original.rkt" "identical.rkt" "different.rkt")
> >> > (begin-for-syntax
> >> >   (unless (free-identifier=? original identical)
> >> >     (error 'fresh "~v != ~v\n" original identical))
> >> >   (when (free-identifier=? original different)
> >> >     (error 'fresh "~v == ~v\n" original different)))
> >> >
> >> > --
> >> > Carl Eastlund
> >> >
> >> > _________________________
> >> >   Racket Developers list:
> >> >   http://lists.racket-lang.org/dev
> >> >
> >>
> >
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.racket-lang.org/dev/archive/attachments/20130531/fa5fd502/attachment.html>