Is it possible to write a macro in Scheme that expands differently depending upon whether the macro was used at the top level or internally? I'm primarily interested in a solution that works in Guile Scheme.
1 Answers
If you mean "internal" in the sense of internal definitions, then it might work to have the macro redefine itself in the nested scope.
(define inner-transformer
(syntax-rules ()
[(_ (id a ...) e1 e2 ...)
(define (id a ...)
(format #t "inner func ~a\n" 'id)
(let () e1 e2 ...))]))
(define-syntax func
(lambda (x)
(syntax-case x ()
[(k (id a ...) e1 e2 ...)
#'(define (id a ...)
(let-syntax ([k inner-transformer])
(format #t "top func ~a\n" 'id)
(let () e1 e2 ...)))])))
(func (foo x)
(func (bar y)
(func (baz z)
(+ x y z))
(baz y))
(bar x))
(foo 1)
Guile result:
top func foo
inner func bar
inner func baz
$1 = 3
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