Add examples & slight fix for stxparam docs

collects/scribblings/reference/stx-param.scrbl

@@ -1,7 +1,13 @@
 #lang scribble/doc
 @(require "mz.rkt"
+          scribble/eval
           (for-label racket/stxparam racket/stxparam-exptime racket/splicing))
 
+@(define the-eval (make-base-eval))
+@(the-eval '(require racket/stxparam
+                     (only-in racket/control abort)
+                     (for-syntax racket/base)))
+
 @title[#:tag "stxparam"]{Syntax Parameters}
 
 @note-lib-only[racket/stxparam]
@@ -19,10 +25,20 @@ or @racket[syntax-parameter-value] (in a transformer). If
 @racket[expr] produces a procedure of one argument or a
 @racket[make-set!-transformer] result, then @racket[id] can be
 used as a macro. If @racket[expr] produces a
-@racket[rename-transformer] result, then @racket[id] can be
+@racket[make-rename-transformer] result, then @racket[id] can be
 used as a macro that expands to a use of the target identifier, but
 @racket[syntax-local-value] of @racket[id] does not produce
-the target's value.}
+the target's value.
+
+@defexamples[#:eval the-eval
+  (define-syntax-parameter current-class #f)
+  (define-syntax-parameter yield (make-rename-transformer #'abort))
+  (define-syntax-parameter define/public
+    (λ (stx)
+      (raise-syntax-error #f "use of a class keyword not in a class" stx)))
+  (begin-for-syntax (displayln (syntax-parameter-value #'current-class)))
+  (yield 5)
+]}
 
 @defform[(syntax-parameterize ([id expr] ...) body-expr ...+)]{
 
@@ -38,10 +54,31 @@ If an @racket[expr] produces a procedure of one argument or a
 @racket[make-set!-transformer] result, then its @racket[id]
 can be used as a macro during the expansion of the
 @racket[body-expr]s. If @racket[expr] produces a
-@racket[rename-transformer] result, then @racket[id] can be
+@racket[make-rename-transformer] result, then @racket[id] can be
 used as a macro that expands to a use of the target identifier, but
 @racket[syntax-local-value] of @racket[id] does not produce
-the target's value.}
+the target's value.
+
+@defexamples[#:eval the-eval
+(define-syntax-parameter abort (syntax-rules ()))
+
+(define-syntax forever
+  (syntax-rules ()
+    [(forever body ...)
+     (call/cc (lambda (abort-k)
+       (syntax-parameterize
+           ([abort (syntax-rules () [(_) (abort-k)])])
+         (let loop () body ... (loop)))))]))
+
+(define-syntax-parameter it (syntax-rules ()))
+
+(define-syntax aif
+  (syntax-rules ()
+    [(aif test then else)
+     (let ([t test])
+       (syntax-parameterize ([it (syntax-id-rules () [_ t])])
+         (if t then else)))]))
+]}
 
 @; ----------------------------------------------------------------------
 
@@ -88,3 +125,5 @@ This binding is provided @racket[for-syntax] by
 @racketmodname[racket/stxparam], since it is normally used in a
 transformer. It is provided normally by
 @racketmodname[racket/stxparam-exptime].}
+
+@(close-eval the-eval)