I ran across some behavior that I find a little bit surprising. Consider the
following module:
#lang racket/base
; the definition of some-fn
(module a racket/base
(provide some-fn)
(define (some-fn) (void)))
; provides some-fn in multiple phase levels
(module b racket/base
(require (submod ".." a)
(for-syntax (submod ".." a)))
(provide some-fn
(for-syntax some-fn)))
; excludes some-fn in phase 0... and phase 1?!
(module c racket/base
(require (except-in (submod ".." b) some-fn))
(provide (all-from-out (submod ".." b))))
(require 'c)
(begin-for-syntax
; not defined!
some-fn)
This demonstrates that except-in appears to remove identifiers from *all* phase
levels, not just phase 0. Is there any way to restrict except-in to a
particular phase level, or is there a different way to accomplish that sort of
behavior?
For context, I ran into this while seeing what it would be like to create an
“r5rs+” lang that permits things like ‘syntax-case’, so I effectively want to
provide all the bindings from ‘r5rs’, but I want to exclude the ‘#%top’,
‘#%datum’, and ‘#%app’ bindings that r5rs exports for phase 1, which restrict
expressions in phase 1 to only use syntax-rules (I’d replace these with the
normal bindings exported for phase 0).
Alexis
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