improved printing a little bit for stepper and traces

svn: r11322

collects/redex/private/size-snip.ss

@@ -19,10 +19,15 @@
                     (λ (val display? op)
                       (cond
                         [(hole? val) 4]
+                        [(eq? val 'hole) 6]
                         [else #f]))]
                    [pretty-print-print-hook
                     (λ (val display? op)
-                      (display "hole" op))])
+                      (cond
+                        [(hole? val)
+                         (display "hole" op)]
+                        [(eq? val 'hole) 
+                         (display ",'hole" op)]))])
       (pretty-print v port)))
   
   (define reflowing-snip<%>

collects/redex/redex.scrbl

@@ -1138,6 +1138,13 @@ These four parameters control the color of the edges in the graph.
 This is the default value of @scheme[pp] used by @scheme[traces] and
 @scheme[stepper] and it uses
 @scheme[pretty-print].
+
+It sets the @scheme[pretty-print-columns] parameter to
+@scheme[width], and it sets @scheme[pretty-print-size-hook]
+and @scheme[pretty-print-print-hook] to print holes and the
+symbol @scheme['hole] to match the way they are input in a
+@scheme[term] expression.
+
 }
 
 @section{Typesetting}