From debd6026f39d10306187477514ce93f0c4eaa45e Mon Sep 17 00:00:00 2001
From: Jay McCarthy <jay@racket-lang.org>
Date: Thu, 12 Aug 2010 14:54:48 -0600
Subject: [PATCH] Fixing a few bugs from drdr

---
 collects/racket/list.rkt             | 10 +++++++++-
 collects/racket/private/list.rkt     | 17 +----------------
 collects/racket/private/sequence.rkt |  5 +++--
 3 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/collects/racket/list.rkt b/collects/racket/list.rkt
index 1571f28478..9265380c1e 100644
--- a/collects/racket/list.rkt
+++ b/collects/racket/list.rkt
@@ -1,5 +1,5 @@
 #lang scheme/base
-(require (only-in "private/list.rkt" split-at))
+
 (provide first second third fourth fifth sixth seventh eighth ninth tenth
 
          last-pair last rest
@@ -107,6 +107,14 @@
           [(pair? list) (cons (car list) (loop (cdr list) (sub1 n)))]
           [else (too-large 'take list0 n0)])))
 
+(define (split-at list0 n0)
+  (unless (exact-nonnegative-integer? n0)
+    (raise-type-error 'split-at "non-negative exact integer" n0))
+  (let loop ([list list0] [n n0] [pfx '()])
+    (cond [(zero? n) (values (reverse pfx) list)]
+          [(pair? list) (loop (cdr list) (sub1 n) (cons (car list) pfx))]
+          [else (too-large 'split-at list0 n0)])))
+
 (define (drop list n)
   ;; could be defined as `list-tail', but this is better for errors anyway
   (unless (exact-nonnegative-integer? n)
diff --git a/collects/racket/private/list.rkt b/collects/racket/private/list.rkt
index c22b59dd70..a943d07e07 100644
--- a/collects/racket/private/list.rkt
+++ b/collects/racket/private/list.rkt
@@ -1,9 +1,7 @@
 
 (module list "pre-base.rkt"
 
-  (provide split-at
-           
-           foldl
+  (provide foldl
            foldr
 
            remv
@@ -26,19 +24,6 @@
            build-list
 
            compose)
-  
-  (define (split-at list0 n0)
-    (unless (exact-nonnegative-integer? n0)
-      (raise-type-error 'split-at "non-negative exact integer" n0))
-    (let loop ([list list0] [n n0] [pfx '()])
-      (cond [(zero? n) (values (reverse pfx) list)]
-            [(pair? list) (loop (cdr list) (sub1 n) (cons (car list) pfx))]
-            [else 
-             (raise-mismatch-error
-              'split-at
-              (format "index ~e too large for list~a: "
-                      n0 (if (list? list0) "" " (not a proper list)"))
-              list0)])))
 
   (#%require (rename "sort.rkt" raw-sort sort)
              (for-syntax "stxcase-scheme.rkt"))
diff --git a/collects/racket/private/sequence.rkt b/collects/racket/private/sequence.rkt
index eeb1c40028..972f0d2258 100644
--- a/collects/racket/private/sequence.rkt
+++ b/collects/racket/private/sequence.rkt
@@ -39,8 +39,9 @@
       [(v s)
        (-seqn-cons (values v) s)]
       [vs*s
-       (define-values (vs sl) (split-at vs*s (sub1 (length vs*s))))
-       (-seqn-cons (apply values vs) (car sl))]))
+       ; XXX double reverse is bad but moving split-at causes a problem I can't figure
+       (define s*vs (reverse vs*s))
+       (-seqn-cons (apply values (reverse (cdr s*vs))) (car s*vs))]))
   
   (define (seqn-first s)
     (define-values (more? next) (sequence-generate s))