From 2ac16f4c8218e57302dfc2415cc6e3f4d9859c82 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 10 Jul 2015 23:17:48 -0400
Subject: [PATCH 1/2] add sublist-lens

---
 unstable/lens/sublist.rkt | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 unstable/lens/sublist.rkt

diff --git a/unstable/lens/sublist.rkt b/unstable/lens/sublist.rkt
new file mode 100644
index 0000000..80c87f4
--- /dev/null
+++ b/unstable/lens/sublist.rkt
@@ -0,0 +1,19 @@
+#lang racket/base
+
+(provide sublist-lens)
+
+(require lens/base/main
+         lens/list/main
+         )
+(module+ test
+  (require rackunit))
+
+(define (sublist-lens i j)
+  (lens-thrush (take-lens j) (drop-lens i)))
+
+(module+ test
+  (check-equal? (lens-view (sublist-lens 1 4) '(0 1 2 3 4 5))
+                '(1 2 3))
+  (check-equal? (lens-set (sublist-lens 1 4) '(0 1 2 3 4 5) '(a b c))
+                '(0 a b c 4 5))
+  )

From 9382b739fe2fa166dcd0e5e1e5d921ea5cf65bb6 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 10 Jul 2015 23:32:14 -0400
Subject: [PATCH 2/2] document sublist-lens and add it to unstable/lens

---
 unstable/lens/main.rkt      |  8 ++++++--
 unstable/lens/main.scrbl    |  1 +
 unstable/lens/sublist.scrbl | 13 +++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 unstable/lens/sublist.scrbl

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index b657015..3ffba54 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -4,10 +4,14 @@
          "compound.rkt"
          "list.rkt"
          "hash.rkt"
-         "view-set.rkt")
+         "view-set.rkt"
+         "sublist.rkt"
+         )
 
 (provide (all-from-out "syntax.rkt"
                        "compound.rkt"
                        "list.rkt"
                        "hash.rkt"
-                       "view-set.rkt"))
+                       "view-set.rkt"
+                       "sublist.rkt"
+                       ))
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 90299a2..3b525f3 100644
--- a/unstable/lens/main.scrbl
+++ b/unstable/lens/main.scrbl
@@ -14,3 +14,4 @@ this library being backwards-compatible.
 @include-section["list.scrbl"]
 @include-section["hash.scrbl"]
 @include-section["syntax.scrbl"]
+@include-section["sublist.scrbl"]
diff --git a/unstable/lens/sublist.scrbl b/unstable/lens/sublist.scrbl
new file mode 100644
index 0000000..c78be0b
--- /dev/null
+++ b/unstable/lens/sublist.scrbl
@@ -0,0 +1,13 @@
+#lang scribble/manual
+
+@(require lens/doc-util/main)
+
+@title{Sublist lenses}
+
+@defmodule[unstable/lens/sublist]
+
+@defproc[(sublist-lens [i exact-nonnegative-integer?] [j exact-nonnegative-integer?]) lens?]{
+@lenses-unstable-examples[
+  (lens-view (sublist-lens 1 4) '(0 1 2 3 4 5))
+  (lens-set (sublist-lens 1 4) '(0 1 2 3 4 5) '(a b c))
+]}