From 3c2db6c1a9037102c855cb2e424ac3f91a0e3b09 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 17 Jul 2015 18:13:28 -0400
Subject: [PATCH] provide and document string lenses

---
 unstable/lens/main.rkt     |  2 ++
 unstable/lens/main.scrbl   |  1 +
 unstable/lens/string.scrbl | 23 +++++++++++++++++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 unstable/lens/string.scrbl

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index 93a61f5..63b4650 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -4,6 +4,7 @@
          "join.rkt"
          "list.rkt"
          "hash.rkt"
+         "string.rkt"
          "view-set.rkt"
          "sublist.rkt"
          "struct.rkt"
@@ -15,6 +16,7 @@
                        "join.rkt"
                        "list.rkt"
                        "hash.rkt"
+                       "string.rkt"
                        "view-set.rkt"
                        "sublist.rkt"
                        "struct.rkt"
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 2800730..b675413 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["string.scrbl"]
 @include-section["syntax.scrbl"]
 @include-section["sublist.scrbl"]
 @include-section["struct.scrbl"]
diff --git a/unstable/lens/string.scrbl b/unstable/lens/string.scrbl
new file mode 100644
index 0000000..e4fe2f8
--- /dev/null
+++ b/unstable/lens/string.scrbl
@@ -0,0 +1,23 @@
+#lang scribble/manual
+
+@(require lens/doc-util/main)
+
+@title{String Lenses}
+
+@defproc[(string-ref-lens [i exact-nonnegative-integer?]) lens?]{
+Returns a lens for viewing the @racket[i]th character of a string.
+@lenses-unstable-examples[
+  (lens-view (string-ref-lens 2) "abcdef")
+  (lens-set (string-ref-lens 2) "abcdef" #\C)
+]}
+
+@defproc[(string-pluck-lens [i exact-nonnegative-integer?]) lens?]{
+Like @racket[list-refs-lens], but for strings.
+Equivalent to @racket[(lens-join/string (string-ref-lens i) ...)].
+@lenses-unstable-examples[
+  (define 1-5-6-lens (string-pluck-lens 1 5 6))
+  (check-equal? (lens-view 1-5-6-lens "abcdefg")
+                "bfg")
+  (check-equal? (lens-set 1-5-6-lens "abcdefg" "BFG")
+                "aBcdeFG")
+]}