commit 65d06802cac532feffefabbb762e6f5a51c8a7ac
parent 9620db724eea4d9d60b27f690961b11d0fa3f5c3
Author: Greg Hendershott <greghendershott@gmail.com>
Date: Fri, 2 Nov 2012 11:44:33 -0400
Re-org the (require (for-syntax racket/match)) example.
Diffstat:
| M | main.rkt | | | 30 | ++++++++++++++++++------------ |
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/main.rkt b/main.rkt
@@ -496,21 +496,27 @@ We can write:
(match (syntax->list stx)
[(list name condition true-expr false-expr)
(datum->syntax stx `(cond [,condition ,true-expr]
- [else ,false-expr]))]))
+ [else ,false-expr]))]))]
+
+Great. Now let's try using it:
+
+@i[
(our-if-using-match #t "true" "false")
]
-But wait, we can't. It's complaining that @racket[match] isn't
-defined. We haven't required the @racket[racket/match] module?
-
-It turns out we haven't. Remember, this transformer function is
-working at compile time, not run time. And at compile time, only
-@racket[racket/base] is required for you automatically. If we want
-something like @racket[racket/match], we have to require it
-ourselves---and require it @italic{for compile time}. Instead of using
-plain @racket[(require racket/match)], the way to say this is to use
-@racket[(require (for-syntax racket/match))]---the @racket[for-syntax]
-part meaning, "for compile time".
+Oops. It's complaining that @racket[match] isn't defined.
+
+Our transformer function is working at compile time, not run time. And
+at compile time, only @racket[racket/base] is required for you
+automatically---not the full @racket[racket].
+
+Anything beyond @racket[racket/base], we have to require
+ourselves---and require it for compile time using the
+@racket[for-syntax] form of @racket[require].
+
+In this case, instead of using plain @racket[(require racket/match)],
+we want @racket[(require (for-syntax racket/match))]---the
+@racket[for-syntax] part meaning, "for compile time".
So let's try that:
