From 6e50ecad9973423d284216e4ee287271627d4468 Mon Sep 17 00:00:00 2001
From: Eli Barzilay <eli@barzilay.org>
Date: Fri, 26 Aug 2011 09:42:56 -0400
Subject: [PATCH] Add `$1', `$2', ..., `$5' as last-value references.

---
 collects/tests/xrepl/xrepl.rkt |  2 ++
 collects/xrepl/xrepl.rkt       | 32 +++++++++++++++++++-------------
 collects/xrepl/xrepl.scrbl     |  9 ++++++---
 3 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/collects/tests/xrepl/xrepl.rkt b/collects/tests/xrepl/xrepl.rkt
index 1af636c0f6..40afaf2f72 100644
--- a/collects/tests/xrepl/xrepl.rkt
+++ b/collects/tests/xrepl/xrepl.rkt
@@ -87,6 +87,8 @@
   4
   -> «(list ^ ^^ ^^^ ^^^^)»
   '(4 3 2 1)
+  -> «(list $1 $2 $3 $4 $5)»
+  '((4 3 2 1) 4 3 2 1)
   -> «(collect-garbage)»
   -> «^»
   ; ^: saved value #1 was garbage-collected [,bt for context]
diff --git a/collects/xrepl/xrepl.rkt b/collects/xrepl/xrepl.rkt
index 263d3f47fa..9272818264 100644
--- a/collects/xrepl/xrepl.rkt
+++ b/collects/xrepl/xrepl.rkt
@@ -3,10 +3,10 @@
 ;; ----------------------------------------------------------------------------
 ;; customization
 
-(define toplevel-prefix     (make-parameter "-")) ; when not in a module
-(define saved-values-number (make-parameter 5))
-(define saved-values-char   (make-parameter #\^))
-(define wrap-column         (make-parameter 79))
+(define toplevel-prefix       (make-parameter "-")) ; when not in a module
+(define saved-values-number   (make-parameter 5))
+(define saved-values-patterns (make-parameter '("^" "$~a")))
+(define wrap-column           (make-parameter 79))
 ;; TODO: when there's a few more of these, make them come from the prefs
 
 ;; ----------------------------------------------------------------------------
@@ -1209,16 +1209,22 @@
 
 (define last-saved-names+state (make-parameter '(#f #f #f)))
 (define (get-saved-names)
-  (define last      (last-saved-names+state))
-  (define last-num  (cadr last))
-  (define last-char (caddr last))
-  (define cur-num   (saved-values-number))
-  (define cur-char  (saved-values-char))
-  (if (and (equal? last-num cur-num) (equal? last-char cur-char))
+  (define last       (last-saved-names+state))
+  (define last-num   (cadr last))
+  (define last-ptrns (caddr last))
+  (define cur-num    (saved-values-number))
+  (define cur-ptrns  (saved-values-patterns))
+  (if (and (equal? last-num cur-num) (equal? last-ptrns cur-ptrns))
     (car last)
-    (let ([new (for/list ([i (in-range (saved-values-number))])
-                 (string->symbol (make-string (add1 i) (saved-values-char))))])
-      (last-saved-names+state (list new cur-num cur-char))
+    (let ([new
+           (for*/list ([i (in-range 1 (add1 (saved-values-number)))]
+                       [p (in-list cur-ptrns)])
+             (string->symbol
+              (cond
+                [(= 1 (string-length p)) (make-string i (string-ref p 0))]
+                [(regexp-match? #rx"^[^~]*~a[^~]*$" p) (format p i)]
+                [else (error 'saved-names "bad name pattern: ~e" p)])))])
+      (last-saved-names+state (list new cur-num cur-ptrns))
       new)))
 
 ;; see comment at the top of this module for the below hair
diff --git a/collects/xrepl/xrepl.scrbl b/collects/xrepl/xrepl.scrbl
index dd3f5493de..68b019eaf6 100644
--- a/collects/xrepl/xrepl.scrbl
+++ b/collects/xrepl/xrepl.scrbl
@@ -451,9 +451,12 @@ The rationale for this is that @racketidfont{^} always refers to the
 last @emph{printed} result, @racketidfont{^^} to the one before that,
 etc.
 
-The bindings are made available only if they are not already defined.
-This means that if you have code that uses these names, it will continue
-to work as usual.
+In addition to these names, XREPL also binds @racketidfont{$1},
+@racketidfont{$2}, ..., @racketidfont{$5} to the same references, so you
+can choose the style that you like.  All of these bindings are made
+available only if they are not already defined.  This means that if you
+have code that uses these names, it will continue to work as usual (and
+it will shadow the saved value binding).
 
 The bindings are identifier macros that expand to the literal saved
 values; so referring to a saved value that is missing (because not