OK, I sat down and re-read:
https://docs.racket-lang.org/guide/phases.html
Then I noticed I made a stupid mistake in my first attempt. I didn't
need to provide the binding at different levels, I needed only to
require it at different levels. So doing
(require s10/arch-choice
(for-syntax s10/arch-choice))
did the trick.
Thanks for your time helping me with this issue.
Kind regards,
Paulo Matos
On 13/09/2018 14:28, 'Paulo Matos' via Racket Users wrote:
>
>
> On 12/09/2018 16:37, Matthew Flatt wrote:
>> As you
>> say, you could have a macro expand to the result of `(getenv "ARCH")`
>> to pin it down at compile time, but you'll need to import that macro
>> into two phases, since the right-hand side of
>> `define-runtime-module-path-index` is implicitly used at two phases.
>
> Thanks for your thorough explanation of the issues. That clarified it
> completely.
>
> I have got it to working and realised that actually a compile time
> configuration is more future-proof in case I end up developing a private
> backend for a customer which I should ship to another customer by
> mistake, therefore embedding a single backend per release is better.
>
> I setup a file which does this to choose the backend at compile-time:
> #lang racket/base
> ;;
> ---------------------------------------------------------------------------------------------------
>
> (require (for-syntax racket/base))
>
> (provide get-configured-backend-path)
>
> ;;
> ---------------------------------------------------------------------------------------------------
> ;; This module is used to move the compile time variable s10arch, read
> from the environment
> ;; to a build-time variable using a macro.
>
> (begin-for-syntax
> ;; An environment variable must be defined selecting the arch to use.
> (define s10arch (getenv "S10ARCH"))
>
> (unless s10arch
> (raise-user-error 'driver "Please define S10ARCH environment
> variable")))
>
> (define-syntax (get-configured-backend-path stx)
> (syntax-case stx ()
> [(_) (datum->syntax stx s10arch)]))
>
>
> Then from another module I am doing:
> (require s10/arch-choice)
>
> (define-runtime-module-path-index backend-path
> (build-path (get-configured-backend-path) "name.rkt"))
>
> However the problem here is that get-configured-backend-path does not
> exist in level0 - only in level1.
>
> I tried to provide it then like so:
> (provide get-configured-backend-path
> (for-syntax get-configured-backend-path))
>
> and then require it for syntax as well in the driver module, however
> this generates the strange:
> s10/arch-choice.rkt:7:21: provide: provided identifier is not defined or
> required
>
> How can get get-configured-backend-path to exist at both level which
> seems to be what define-runtime-module-path-index requires?
>
>
--
Paulo Matos
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