From 441d790844ce7d6dae466ebab1e24262dc50e98d Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Sun, 16 Aug 2015 17:21:09 -0500
Subject: [PATCH] provide and document mapper-lens

---
 unstable/lens/main.rkt     |  2 ++
 unstable/lens/main.scrbl   |  1 +
 unstable/lens/mapper.scrbl | 15 +++++++++++++++
 3 files changed, 18 insertions(+)
 create mode 100644 unstable/lens/mapper.scrbl

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index c02a2bc..e79e14f 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -5,6 +5,7 @@
          "sublist.rkt"
          "arrow.rkt"
          "isomorphism.rkt"
+         "mapper.rkt"
          )
 
 (provide (all-from-out "syntax.rkt"
@@ -12,4 +13,5 @@
                        "sublist.rkt"
                        "arrow.rkt"
                        "isomorphism.rkt"
+                       "mapper.rkt"
                        ))
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 26e8f30..bf07f06 100644
--- a/unstable/lens/main.scrbl
+++ b/unstable/lens/main.scrbl
@@ -14,3 +14,4 @@ this library being backwards-compatible.
 @include-section["sublist.scrbl"]
 @include-section["arrow.scrbl"]
 @include-section["isomorphism.scrbl"]
+@include-section["mapper.scrbl"]
diff --git a/unstable/lens/mapper.scrbl b/unstable/lens/mapper.scrbl
new file mode 100644
index 0000000..797c2df
--- /dev/null
+++ b/unstable/lens/mapper.scrbl
@@ -0,0 +1,15 @@
+#lang scribble/manual
+
+@(require lens/doc-util/main)
+
+@title{Lenses that map over lists}
+
+@defmodule[unstable/lens/mapper]
+
+@defproc[(mapper-lens [lens lens?]) lens?]{
+Creates a lens that maps @racket[lens] over a target list.
+@lenses-unstable-examples[
+  (lens-view (mapper-lens first-lens) '((a b) (c d) (e f)))
+  (lens-set (mapper-lens first-lens) '((a b) (c d) (e f)) '(1 2 3))
+  (lens-transform (mapper-lens first-lens) '((a b) (c d) (e f)) (λ (xs) (map symbol->string xs)))
+]}