From 68a4c2d76aa2c3b9060735fa3fdf9fbd6bb045f3 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 17 Jul 2015 16:09:32 -0400
Subject: [PATCH 1/3] make lens-join/vector use immutable vectors

---
 unstable/lens/join.rkt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/unstable/lens/join.rkt b/unstable/lens/join.rkt
index 3420773..ae51267 100644
--- a/unstable/lens/join.rkt
+++ b/unstable/lens/join.rkt
@@ -84,8 +84,11 @@
    (λ (tgt) (f tgt))
    (λ (tgt v) (f-inv v))))
 
+(define (list->immutable-vector lst)
+  (apply vector-immutable lst))
+
 (define list->vector-lens
-  (inverse-function-lens list->vector vector->list))
+  (inverse-function-lens list->immutable-vector vector->list))
 
 (module+ test
   (define vector-first-third-fifth-lens
@@ -94,6 +97,7 @@
                       fifth-lens))
   (check-equal? (lens-view vector-first-third-fifth-lens '(a b c d e f))
                 #(a c e))
+  (check-pred immutable? (lens-view vector-first-third-fifth-lens '(a b c d e f)))
   (check-equal? (lens-set vector-first-third-fifth-lens '(a b c d e f) #(1 2 3))
                 '(1 b 2 d 3 f)))
 

From 2ac7ac78086450eac4bc7cdfcd3c4ae8446c2f56 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 17 Jul 2015 16:29:22 -0400
Subject: [PATCH 2/3] add vector-ref-lens, vector-ref-nested-lens, and
 vector-pluck-lens

---
 unstable/lens/vector.rkt | 50 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 unstable/lens/vector.rkt

diff --git a/unstable/lens/vector.rkt b/unstable/lens/vector.rkt
new file mode 100644
index 0000000..7eefbd6
--- /dev/null
+++ b/unstable/lens/vector.rkt
@@ -0,0 +1,50 @@
+#lang racket/base
+
+(provide vector-ref-lens
+         vector-ref-nested-lens
+         vector-pluck-lens
+         )
+
+(require fancy-app
+         lens/base/main
+         "arrow.rkt"
+         "join.rkt"
+         )
+(module+ test
+  (require rackunit))
+
+(define (vector-ref-lens i)
+  (make-lens
+   (vector-ref _ i)
+   (vector-set _ i _)))
+
+(define (vector-set v i x)
+  (vector->immutable-vector
+   (build-vector (vector-length v)
+                 (λ (j)
+                   (if (= i j)
+                       x
+                       (vector-ref v j))))))
+
+(define (vector-ref-nested-lens . is)
+  (apply lens-thrush (map vector-ref-lens is)))
+
+(define (vector-pluck-lens . is)
+  (apply lens-join/vector (map vector-ref-lens is)))
+
+
+(module+ test
+  (check-equal? (lens-view (vector-ref-lens 0) #(a b c)) 'a)
+  (check-equal? (lens-view (vector-ref-lens 1) #(a b c)) 'b)
+  (check-equal? (lens-view (vector-ref-lens 2) #(a b c)) 'c)
+  (check-equal? (lens-set (vector-ref-lens 0) #(a b c) "A") #("A" b c))
+  (check-equal? (lens-set (vector-ref-lens 1) #(a b c) "B") #(a "B" c))
+  (check-equal? (lens-set (vector-ref-lens 2) #(a b c) "C") #(a b "C"))
+  (check-equal? (lens-transform (vector-ref-nested-lens 2 1) #(a #(b c) #(d e f)) symbol->string)
+                #(a #(b c) #(d "e" f)))
+  (define 1-5-6-lens (vector-pluck-lens 1 5 6))
+  (check-equal? (lens-view 1-5-6-lens #(a b c d e f g))
+                #(b f g))
+  (check-equal? (lens-set 1-5-6-lens #(a b c d e f g) #(1 2 3))
+                #(a 1 c d e 2 3))
+  )

From a5283474bd195798e1c9a89191e61bb20d384b39 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 17 Jul 2015 18:02:09 -0400
Subject: [PATCH 3/3] provide and document vector lenses

---
 unstable/lens/main.rkt     |  2 ++
 unstable/lens/main.scrbl   |  1 +
 unstable/lens/vector.scrbl | 31 +++++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+)
 create mode 100644 unstable/lens/vector.scrbl

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index 75a3f97..d755f4d 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -4,6 +4,7 @@
          "join.rkt"
          "list.rkt"
          "hash.rkt"
+         "vector.rkt"
          "string.rkt"
          "view-set.rkt"
          "sublist.rkt"
@@ -17,6 +18,7 @@
                        "join.rkt"
                        "list.rkt"
                        "hash.rkt"
+                       "vector.rkt"
                        "string.rkt"
                        "view-set.rkt"
                        "sublist.rkt"
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 3b5daf3..33d10b2 100644
--- a/unstable/lens/main.scrbl
+++ b/unstable/lens/main.scrbl
@@ -13,6 +13,7 @@ this library being backwards-compatible.
 @include-section["join.scrbl"]
 @include-section["list.scrbl"]
 @include-section["hash.scrbl"]
+@include-section["vector.scrbl"]
 @include-section["string.scrbl"]
 @include-section["syntax.scrbl"]
 @include-section["sublist.scrbl"]
diff --git a/unstable/lens/vector.scrbl b/unstable/lens/vector.scrbl
new file mode 100644
index 0000000..8730b11
--- /dev/null
+++ b/unstable/lens/vector.scrbl
@@ -0,0 +1,31 @@
+#lang scribble/manual
+
+@(require lens/doc-util/main)
+
+@title{Vector lenses}
+
+@defproc[(vector-ref-lens [i exact-nonnegative-integer?]) lens?]{
+Returns a lens that views an element of a vector.
+@lenses-unstable-examples[
+  (lens-view (vector-ref-lens 2) #(a b c d))
+  (lens-set (vector-ref lens 2) #(a b c d) "sea")
+]}
+
+@defproc[(vector-ref-nested-lens [i exact-nonnegative-integer?] ...) lens?]{
+Like @racket[list-ref-nested-lens], but for vectors.
+Equivalent to @racket[(lens-thrush (vector-ref-lens i) ...)].
+@lenses-unstable-examples[
+  (lens-view (vector-ref-nested-lens 2 1) #(a b #(s i) d))
+  (lens-set (vector-ref-nested-lens 2 1) #(a b #(s i) d) "eye")
+]}
+
+@defproc[(vector-pluck-lens [i exact-nonnegative-integer?] ...) lens?]{
+Like @racket[list-refs-lens], but for vectors.
+Equivalent to @racket[(lens-join/vector (vector-ref-lens i) ...)].
+@lenses-unstable-examples[
+  (define 1-5-6-lens (vector-pluck-lens 1 5 6))
+  (check-equal? (lens-view 1-5-6-lens #(a b c d e f g))
+                #(b f g))
+  (check-equal? (lens-set 1-5-6-lens #(a b c d e f g) #(1 2 3))
+                #(a 1 c d e 2 3))
+]}