Re: Using environment-bound? in macro definitions

[Per Bothner <per at bothner dot com>]

On 01/02/2017 03:29 PM, Duncan Mak wrote:
> (require 'syntax-utils)
> (define-for-syntax known (list))
>
> (define-syntax define-foo
>   (lambda (stx)
>     (syntax-case stx ()
>       ((define-foo a)
>        (begin
>          (set! known (cons #'a known))
>          #'(define a (list)))))))
>
> (define-syntax define-bar
>   (lambda (stx)
>     (syntax-case stx ()
>       ((define-bar a n)
>        (if (environment-bound? (apply environment known) #'a)
>            #'(set! a (cons n a))
>            #'(begin
>                (define-foo a)
>                (set! a (cons n a))))))))
>
> ;; (1) should expand to (define x (list)) and store x in known
> (define-foo x)

In other words, at this point:

(equal? known '(x))

test.scm:29:1: evaluating syntax transformer 'define-bar' threw
gnu.text.SyntaxException: <unknown>: unknown library (x)

That means you're evaluating (environment 'x).
The 'x is interpreted as an "environment specifier" - i.e. a library name,
and there is no such library (or class).

I think you misunderstand the 'environment' procedure.  Check the Kawa and R7RS documentation.

What are you trying to do? Trying to dynamically build environment maps
is possible, but there isn't a Scheme API for it, and there are tricky interactions
between the dynamic top-level and the module-level lexical scope.

--
	--Per Bothner
per@bothner.com   http://per.bothner.com/