From ec08ef67dd8ffcb19d8aa7225454a9501dbc911d Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Thu, 3 Sep 2015 02:11:10 -0400
Subject: [PATCH 1/3] add isomorphism-compose and isomorphism-thrush

also take away special case in lens-compose for isomorphisms
---
 lens/private/compound/compose.rkt      | 13 +------------
 unstable/lens/isomorphism.rkt          |  1 +
 unstable/lens/isomorphism.scrbl        | 10 ++++++++++
 unstable/lens/isomorphism/compound.rkt | 18 ++++++++++++++++++
 4 files changed, 30 insertions(+), 12 deletions(-)
 create mode 100644 unstable/lens/isomorphism/compound.rkt

diff --git a/lens/private/compound/compose.rkt b/lens/private/compound/compose.rkt
index 71b0efa..934a1fc 100644
--- a/lens/private/compound/compose.rkt
+++ b/lens/private/compound/compose.rkt
@@ -7,7 +7,6 @@ require racket/contract
         "../base/main.rkt"
         "../util/rest-contract.rkt"
         "identity.rkt"
-        unstable/lens/isomorphism/base
 
 module+ test
   require rackunit
@@ -29,15 +28,7 @@ provide
 
 
 (define (lens-compose . args)
-  (match args
-    [(list)
-     identity-lens]
-    [(list (make-isomorphism-lens fs invs) ...)
-     (make-isomorphism-lens
-      (apply compose1 fs)
-      (apply compose1 (reverse invs)))]
-    [_
-     (foldr lens-compose2 identity-lens args)]))
+  (foldr lens-compose2 identity-lens args))
 
 
 module+ test
@@ -52,5 +43,3 @@ module+ test
   (check-equal? (lens-view first-of-second-lens test-alist) 'b)
   (check-equal? (lens-set first-of-second-lens test-alist 'B) '((a 1) (B 2) (c 3)))
   (check-eq? (lens-compose) identity-lens)
-  (check-pred isomorphism-lens? (lens-compose (make-isomorphism-lens set->list list->set)
-                                              (make-isomorphism-lens list->vector vector->list)))
diff --git a/unstable/lens/isomorphism.rkt b/unstable/lens/isomorphism.rkt
index 7fe763a..6edc5bd 100644
--- a/unstable/lens/isomorphism.rkt
+++ b/unstable/lens/isomorphism.rkt
@@ -1,3 +1,4 @@
 #lang reprovide
 "isomorphism/base.rkt"
+"isomorphism/compound.rkt"
 "isomorphism/data.rkt"
diff --git a/unstable/lens/isomorphism.scrbl b/unstable/lens/isomorphism.scrbl
index bcf0f7f..244da9c 100644
--- a/unstable/lens/isomorphism.scrbl
+++ b/unstable/lens/isomorphism.scrbl
@@ -46,6 +46,16 @@ example, are defined like this:
     (make-isomorphism-lenses string->symbol symbol->string))
 ]}
 
+@defproc[(isomorphism-compose [lens isomorphism-lens?] ...) isomorphism-lens?]{
+Like @racket[lens-compose], but works only on isomorphism lenses, and returns an
+isomorphism lens.
+}
+
+@defproc[(isomorphism-thrush [lens isomorphism-lens?] ...) isomorphism-lens?]{
+Like @racket[lens-thrush], but works only on isomorphism lenses, and returns an
+isomorphism lens.
+}
+
 @deflenses[[string->symbol-lens symbol->string-lens
             number->string-lens string->number-lens
             list->vector-lens vector->list-lens
diff --git a/unstable/lens/isomorphism/compound.rkt b/unstable/lens/isomorphism/compound.rkt
new file mode 100644
index 0000000..26b7d4f
--- /dev/null
+++ b/unstable/lens/isomorphism/compound.rkt
@@ -0,0 +1,18 @@
+#lang sweet-exp racket/base
+
+provide isomorphism-compose
+        isomorphism-thrush
+
+require racket/match
+        "base.rkt"
+
+(define (isomorphism-compose . args)
+  (match args
+    [(list (make-isomorphism-lens fs invs) ...)
+     (make-isomorphism-lens
+      (apply compose1 fs)
+      (apply compose1 (reverse invs)))]))
+
+(define (isomorphism-thrush . args)
+  (apply isomorphism-compose (reverse args)))
+

From 7e512ada886eb157a220c4225dcfe7a7bdf51a5b Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Thu, 3 Sep 2015 16:24:05 -0400
Subject: [PATCH 2/3] add contracts and tests for isomorphism-compose and
 -thrush

---
 unstable/lens/isomorphism/compound.rkt | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/unstable/lens/isomorphism/compound.rkt b/unstable/lens/isomorphism/compound.rkt
index 26b7d4f..c14bd1b 100644
--- a/unstable/lens/isomorphism/compound.rkt
+++ b/unstable/lens/isomorphism/compound.rkt
@@ -1,10 +1,21 @@
 #lang sweet-exp racket/base
 
-provide isomorphism-compose
-        isomorphism-thrush
+require racket/contract/base
+provide
+  contract-out
+    isomorphism-compose
+      (rest-> isomorphism-lens? isomorphism-lens?)
+    isomorphism-thrush
+      (rest-> isomorphism-lens? isomorphism-lens?)
 
 require racket/match
+        lens/private/util/rest-contract
         "base.rkt"
+module+ test
+  require lens/private/base/main
+          lens/private/compound/identity
+          rackunit
+          "data.rkt"
 
 (define (isomorphism-compose . args)
   (match args
@@ -16,3 +27,7 @@ require racket/match
 (define (isomorphism-thrush . args)
   (apply isomorphism-compose (reverse args)))
 
+module+ test
+  (define string->vector-lens (isomorphism-thrush string->list-lens list->vector-lens))
+  (check-equal? (lens-view string->vector-lens "abc") #(#\a #\b #\c))
+  (check-equal? (lens-set string->vector-lens "abc" #(#\1 #\2 #\3)) "123")

From cb2f192ed926b15563193d85defb57520744d2f1 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Thu, 3 Sep 2015 16:27:48 -0400
Subject: [PATCH 3/3] add note about isomorphism-compose being more efficient

---
 unstable/lens/isomorphism.scrbl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/unstable/lens/isomorphism.scrbl b/unstable/lens/isomorphism.scrbl
index 244da9c..5899e2c 100644
--- a/unstable/lens/isomorphism.scrbl
+++ b/unstable/lens/isomorphism.scrbl
@@ -48,12 +48,12 @@ example, are defined like this:
 
 @defproc[(isomorphism-compose [lens isomorphism-lens?] ...) isomorphism-lens?]{
 Like @racket[lens-compose], but works only on isomorphism lenses, and returns an
-isomorphism lens.
+isomorphism lens. It is also more efficient than @racket[lens-compose].
 }
 
 @defproc[(isomorphism-thrush [lens isomorphism-lens?] ...) isomorphism-lens?]{
 Like @racket[lens-thrush], but works only on isomorphism lenses, and returns an
-isomorphism lens.
+isomorphism lens. It is also more efficient than @racket[lens-thrush].
 }
 
 @deflenses[[string->symbol-lens symbol->string-lens