I am using syntax transformers to define macros in Racket. I want to create
some helper functions to help me manipulate the syntax. However, the
functions I defined outside the syntax transformer are not available inside
the syntax transformer. For example, in the following code
(define (my-function x) (+ x 1))
(define-syntax my-macro
(lambda (stx)
(datum->syntax stx (my-function (cadr (syntax->datum stx))))))
I got the error "my-function: reference to an unbound identifier at phase:
1; the transformer environment".
After some searching, I am able to write the following code so that
`my-function` is available inside the syntax transformer.
(begin-for-syntax
(define (my-function x) (+ x 1)))
(provide (for-syntax my-function))
(define-syntax my-macro
(lambda (stx)
(datum->syntax stx (my-function (cadr (syntax->datum stx))))))
But the problem is, `my-function` is not available outside the syntax
transformer this time. Sometimes I want to check those helper functions in
ordinary code, so I need to be able to call it from both inside and outside
the syntax transformer, just like the function `cadr`. How can I achieve
that?
I know my question has something to do with Racket's syntax model, in
particular the concept of "phase level", but I never really understand it.
If you could provide some easy-to-follow tutorials explaining it I would
even be more grateful.
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