> Oh, that's my problem: i obviously don't understand what's the places where
> macro expansion happens.
> I ended up writing "classical" lisp non-hygienic macro instead.
>
> It's a sad thing that I cannot find a book or text as clear as PG's "On
> Lisp" that covers Racket's hygienic macros in such detailed manner. :(
Personally, I rarely use pure template-based macros; I mostly use the
syntax-case system. It's closer to the "old-fashioned" way of doing
things. In the old fashioned way, your macros are functions that take
in s-expression and return s-expressions. In Racket's syntax-case
system, your macros are functions that take in syntax and return
syntax.
For example:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
#lang racket
(define-syntax (with stx)
(syntax-case stx ()
[(_ name value body ...)
(begin
(printf "I am compiling: ~s\n" stx)
(printf "I have destructed the syntaxes: ~s\n~s\n~s\n"
#'name
#'value
#'(body ...))
(let ([result
#'(let ([name value])
body ...)])
(printf "I am going to return ~s to the compiler.\n" result)
result))]))
;; Trying the macro out:
(with x 3 (+ x x))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Just as ' is an abbreviation for quote, #' is an abbreviation for
syntax. Kent Dybvig's tutorial on syntax case was helpful for me:
http://www.cs.indiana.edu/~dyb/pubs/tr356.pdf
It would be nice if there were a document that consolidated the
content of that, but put in the context of Racket rather than just
generally Scheme.
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