From dde85c9796836e1eafe99bee37e3422f9b9e2bcd Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Mon, 31 Aug 2015 15:32:55 -0400
Subject: [PATCH 1/5] add transformer-lens

closes https://github.com/jackfirth/lens/issues/201
---
 unstable/lens/transformer.rkt | 79 +++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 unstable/lens/transformer.rkt

diff --git a/unstable/lens/transformer.rkt b/unstable/lens/transformer.rkt
new file mode 100644
index 0000000..a8ca86b
--- /dev/null
+++ b/unstable/lens/transformer.rkt
@@ -0,0 +1,79 @@
+#lang sweet-exp racket/base
+
+provide transformer-lens
+
+require fancy-app
+        lens/private/base/main
+        racket/match
+        "isomorphism/base.rkt"
+module+ test
+  require lens/private/list/main
+          rackunit
+          "isomorphism/data.rkt"
+          "mapper.rkt"
+
+;; transformer-lens : (Lens (Outer Inner) Inner) (Lens A B) -> (Lens (Outer A) (Outer B))
+(define (transformer-lens lens transformer-lens)
+  (match transformer-lens
+    [(make-isomorphism-lens transformer inverse)
+     ;; transformer : A -> B
+     ;; inverse     : B -> A
+     (make-isomorphism-lens
+      (lens-transform lens _ transformer) ; (Outer A) -> (Outer B)
+      (lens-transform lens _ inverse))]   ; (Outer B) -> (Outer A)
+    [transformer-lens
+     ;; get : (Outer A) -> (Outer B)
+     (define (get tgt)
+       ;; transformer : A -> B
+       (define (transformer a)
+         (lens-view transformer-lens a))
+       (lens-transform lens tgt transformer))
+     ;; set : (Outer A) (Outer B) -> (Outer A)
+     (define (set tgt nvw)
+       ;; a : A
+       (define a (lens-view lens tgt))
+       ;; transformer : B -> A
+       (define (transformer b)
+         (lens-set transformer-lens a b))
+       (lens-transform lens nvw transformer))
+     (make-lens get set)]))
+
+module+ test
+  (define first-sym->str
+    (transformer-lens first-lens symbol->string-lens))
+  (check-equal? (lens-view first-sym->str '(a b c))
+                '("a" b c))
+  (check-equal? (lens-set first-sym->str '(a b c) '("a" b c))
+                '(a b c))
+  (check-equal? (lens-set first-sym->str '(a b c) '("z" b c))
+                '(z b c))
+  (check-equal? (lens-set first-sym->str '(a b c) '("z" bee sea))
+                '(z bee sea))
+  (check-equal? (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
+                '("z" bee sea))
+  (define trans-second-first
+    (transformer-lens second-lens first-lens))
+  (check-equal? (lens-view trans-second-first '(1 (2 3) 4))
+                '(1 2 4))
+  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(1 2 4))
+                '(1 (2 3) 4))
+  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(1 b 4))
+                '(1 (b 3) 4))
+  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(a b c))
+                '(a (b 3) c))
+  (check-equal? (lens-view trans-second-first
+                           (lens-set trans-second-first '(1 (2 3) 4) '(a b c)))
+                '(a b c))
+  (define (rekey-alist-lens key->new-key-lens)
+    (mapper-lens (transformer-lens car-lens key->new-key-lens)))
+  (check-equal? (lens-view (rekey-alist-lens symbol->string-lens) '((a . 1) (b . 2) (c . 3)))
+                '(("a" . 1) ("b" . 2) ("c" . 3)))
+  (check-equal? (lens-set (rekey-alist-lens symbol->string-lens)
+                          '((a . 1) (b . 2) (c . 3))
+                          '(("a" . 10) ("b" . 200) ("c" . 3000)))
+                '((a . 10) (b . 200) (c . 3000)))
+  (check-equal? (lens-set (rekey-alist-lens symbol->string-lens)
+                          '((a . 1) (b . 2) (c . 3))
+                          '(("one" . 10) ("two" . 200) ("three" . 3000)))
+                '((one . 10) (two . 200) (three . 3000)))
+

From c9fa6fb8ea78142e0f529835f82d2026fb90af4b Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Mon, 31 Aug 2015 15:48:38 -0400
Subject: [PATCH 2/5] provide and document transformer-lens

---
 unstable/lens/main.rkt          |  1 +
 unstable/lens/main.scrbl        |  1 +
 unstable/lens/transformer.scrbl | 26 ++++++++++++++++++++++++++
 3 files changed, 28 insertions(+)
 create mode 100644 unstable/lens/transformer.scrbl

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index 4393467..6c69a5e 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -13,4 +13,5 @@
 "struct-nested.rkt"
 "sublist.rkt"
 "syntax.rkt"
+"transformer.rkt"
 "view-set.rkt"
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 10d51a5..2a2d1e9 100644
--- a/unstable/lens/main.scrbl
+++ b/unstable/lens/main.scrbl
@@ -26,6 +26,7 @@ this library being backwards-compatible.
   "struct-nested.scrbl"
   "sublist.scrbl"
   "syntax.scrbl"
+  "transformer.scrbl"
   "view-set.scrbl"
   )
 
diff --git a/unstable/lens/transformer.scrbl b/unstable/lens/transformer.scrbl
new file mode 100644
index 0000000..f6275e5
--- /dev/null
+++ b/unstable/lens/transformer.scrbl
@@ -0,0 +1,26 @@
+#lang scribble/manual
+
+@(require lens/private/doc-util/main)
+
+@title{Lenses that transform subpieces}
+
+@defmodule[unstable/lens/transformer]
+
+@defproc[(transformer-lens [lens lens?] [transform-lens lens?]) lens?]{
+Creates a lens that transforms the subpiece of the target that @racket[lens]
+views with @racket[transform-lens].
+
+@racketblock[(lens-view (transformer-lens lens transform-lens) target)]
+is equivalent to:
+@racketblock[(lens-transform lens target (λ (v) (lens-view transform-lens v)))]
+
+@lens-unstable-examples[
+  (define first-sym->str
+    (transformer-lens first-lens symbol->string-lens))
+  (lens-view first-sym->str '(a b c))
+  (lens-set first-sym->str '(a b c) '("a" b c))
+  (lens-set first-sym->str '(a b c) '("z" b c))
+  (lens-set first-sym->str '(a b c) '("z" bee sea))
+  (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
+]}
+

From 95d6df290d5e4bc2fbaee7b20c1a05bb28e659cf Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Tue, 1 Sep 2015 16:01:05 -0400
Subject: [PATCH 3/5] add transformer-lens*

---
 unstable/lens/transformer.rkt   | 45 ++++++++++++++++++++++++---------
 unstable/lens/transformer.scrbl | 15 +++++++++++
 2 files changed, 48 insertions(+), 12 deletions(-)

diff --git a/unstable/lens/transformer.rkt b/unstable/lens/transformer.rkt
index a8ca86b..c4fb335 100644
--- a/unstable/lens/transformer.rkt
+++ b/unstable/lens/transformer.rkt
@@ -1,10 +1,13 @@
 #lang sweet-exp racket/base
 
 provide transformer-lens
+        transformer-lens*
 
 require fancy-app
         lens/private/base/main
+        lens/private/compound/thrush
         racket/match
+        unstable/sequence
         "isomorphism/base.rkt"
 module+ test
   require lens/private/list/main
@@ -38,6 +41,11 @@ module+ test
        (lens-transform lens nvw transformer))
      (make-lens get set)]))
 
+(define (transformer-lens* . lenses/transformers)
+  (apply lens-thrush
+         (for/list ([args (in-slice 2 lenses/transformers)])
+           (apply transformer-lens args))))
+
 module+ test
   (define first-sym->str
     (transformer-lens first-lens symbol->string-lens))
@@ -51,18 +59,18 @@ module+ test
                 '(z bee sea))
   (check-equal? (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
                 '("z" bee sea))
-  (define trans-second-first
-    (transformer-lens second-lens first-lens))
-  (check-equal? (lens-view trans-second-first '(1 (2 3) 4))
-                '(1 2 4))
-  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(1 2 4))
-                '(1 (2 3) 4))
-  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(1 b 4))
-                '(1 (b 3) 4))
-  (check-equal? (lens-set trans-second-first '(1 (2 3) 4) '(a b c))
-                '(a (b 3) c))
-  (check-equal? (lens-view trans-second-first
-                           (lens-set trans-second-first '(1 (2 3) 4) '(a b c)))
+  (define trans-second-first/third-second
+    (transformer-lens* second-lens first-lens third-lens second-lens))
+  (check-equal? (lens-view trans-second-first/third-second '(1 (2 3) (4 5)))
+                '(1 2 5))
+  (check-equal? (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(1 2 5))
+                '(1 (2 3) (4 5)))
+  (check-equal? (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(1 b 5))
+                '(1 (b 3) (4 5)))
+  (check-equal? (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(a b c))
+                '(a (b 3) (4 c)))
+  (check-equal? (lens-view trans-second-first/third-second
+                           (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(a b c)))
                 '(a b c))
   (define (rekey-alist-lens key->new-key-lens)
     (mapper-lens (transformer-lens car-lens key->new-key-lens)))
@@ -76,4 +84,17 @@ module+ test
                           '((a . 1) (b . 2) (c . 3))
                           '(("one" . 10) ("two" . 200) ("three" . 3000)))
                 '((one . 10) (two . 200) (three . 3000)))
+  (define (rek+v-alist-lens key->new-key-lens value->new-value-lens)
+    (mapper-lens (transformer-lens* car-lens key->new-key-lens cdr-lens value->new-value-lens)))
+  (check-equal? (lens-view (rek+v-alist-lens symbol->string-lens number->string-lens)
+                           '((a . 1) (b . 2) (c . 3)))
+                '(("a" . "1") ("b" . "2") ("c" . "3")))
+  (check-equal? (lens-set (rek+v-alist-lens symbol->string-lens number->string-lens)
+                          '((a . 1) (b . 2) (c . 3))
+                          '(("a" . "10") ("b" . "200") ("c" . "3000")))
+                '((a . 10) (b . 200) (c . 3000)))
+  (check-equal? (lens-set (rek+v-alist-lens symbol->string-lens number->string-lens)
+                          '((a . 1) (b . 2) (c . 3))
+                          '(("one" . "10") ("two" . "200") ("three" . "3000")))
+                '((one . 10) (two . 200) (three . 3000)))
 
diff --git a/unstable/lens/transformer.scrbl b/unstable/lens/transformer.scrbl
index f6275e5..c47df3a 100644
--- a/unstable/lens/transformer.scrbl
+++ b/unstable/lens/transformer.scrbl
@@ -24,3 +24,18 @@ is equivalent to:
   (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
 ]}
 
+@defproc[(transformer-lens* [lens lens?] [transform-lens lens?] ... ...) lens?]{
+A multi-arg version of @racket[transformer-lens], analogous to
+@racket[lens-transform/list]. It is equivalent to
+@racket[(lens-thrush (transformer-lens lens transform-lens) ...)].
+@lens-unstable-examples[
+  (define first-sym->str/second-num->str
+    (transformer-lens* first-lens symbol->string-lens second-lens number->string-lens))
+  (lens-view first-sym->str/second-num->str '(a 2 c))
+  (lens-set first-sym->str/second-num->str '(a 2 c) '("a" "2" c))
+  (lens-set first-sym->str/second-num->str '(a 2 c) '("z" "3" c))
+  (lens-set first-sym->str/second-num->str '(a 2 c) '("z" "3" sea))
+  (lens-view first-sym->str/second-num->str
+             (lens-set first-sym->str/second-num->str '(a 2 c) '("z" "3" sea)))
+]}
+

From 96c501dca4e9930cddca6628023b239227e9a601 Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 4 Sep 2015 23:27:03 -0400
Subject: [PATCH 4/5] rename to lens-zoom

---
 unstable/lens/main.rkt                        |  2 +-
 unstable/lens/main.scrbl                      |  2 +-
 unstable/lens/{transformer.rkt => zoom.rkt}   | 30 +++++++++----------
 .../lens/{transformer.scrbl => zoom.scrbl}    | 20 ++++++-------
 4 files changed, 27 insertions(+), 27 deletions(-)
 rename unstable/lens/{transformer.rkt => zoom.rkt} (81%)
 rename unstable/lens/{transformer.scrbl => zoom.scrbl} (62%)

diff --git a/unstable/lens/main.rkt b/unstable/lens/main.rkt
index 6c69a5e..80a7828 100644
--- a/unstable/lens/main.rkt
+++ b/unstable/lens/main.rkt
@@ -13,5 +13,5 @@
 "struct-nested.rkt"
 "sublist.rkt"
 "syntax.rkt"
-"transformer.rkt"
 "view-set.rkt"
+"zoom.rkt"
diff --git a/unstable/lens/main.scrbl b/unstable/lens/main.scrbl
index 2a2d1e9..933da27 100644
--- a/unstable/lens/main.scrbl
+++ b/unstable/lens/main.scrbl
@@ -26,7 +26,7 @@ this library being backwards-compatible.
   "struct-nested.scrbl"
   "sublist.scrbl"
   "syntax.scrbl"
-  "transformer.scrbl"
   "view-set.scrbl"
+  "zoom.scrbl"
   )
 
diff --git a/unstable/lens/transformer.rkt b/unstable/lens/zoom.rkt
similarity index 81%
rename from unstable/lens/transformer.rkt
rename to unstable/lens/zoom.rkt
index c4fb335..996843c 100644
--- a/unstable/lens/transformer.rkt
+++ b/unstable/lens/zoom.rkt
@@ -1,7 +1,7 @@
 #lang sweet-exp racket/base
 
-provide transformer-lens
-        transformer-lens*
+provide lens-zoom
+        lens-zoom*
 
 require fancy-app
         lens/private/base/main
@@ -15,40 +15,40 @@ module+ test
           "isomorphism/data.rkt"
           "mapper.rkt"
 
-;; transformer-lens : (Lens (Outer Inner) Inner) (Lens A B) -> (Lens (Outer A) (Outer B))
-(define (transformer-lens lens transformer-lens)
+;; lens-zoom : (Lens (Outer Inner) Inner) (Lens A B) -> (Lens (Outer A) (Outer B))
+(define (lens-zoom zoom-lens transformer-lens)
   (match transformer-lens
     [(make-isomorphism-lens transformer inverse)
      ;; transformer : A -> B
      ;; inverse     : B -> A
      (make-isomorphism-lens
-      (lens-transform lens _ transformer) ; (Outer A) -> (Outer B)
-      (lens-transform lens _ inverse))]   ; (Outer B) -> (Outer A)
+      (lens-transform zoom-lens _ transformer) ; (Outer A) -> (Outer B)
+      (lens-transform zoom-lens _ inverse))]   ; (Outer B) -> (Outer A)
     [transformer-lens
      ;; get : (Outer A) -> (Outer B)
      (define (get tgt)
        ;; transformer : A -> B
        (define (transformer a)
          (lens-view transformer-lens a))
-       (lens-transform lens tgt transformer))
+       (lens-transform zoom-lens tgt transformer))
      ;; set : (Outer A) (Outer B) -> (Outer A)
      (define (set tgt nvw)
        ;; a : A
-       (define a (lens-view lens tgt))
+       (define a (lens-view zoom-lens tgt))
        ;; transformer : B -> A
        (define (transformer b)
          (lens-set transformer-lens a b))
-       (lens-transform lens nvw transformer))
+       (lens-transform zoom-lens nvw transformer))
      (make-lens get set)]))
 
-(define (transformer-lens* . lenses/transformers)
+(define (lens-zoom* . lenses/transformers)
   (apply lens-thrush
          (for/list ([args (in-slice 2 lenses/transformers)])
-           (apply transformer-lens args))))
+           (apply lens-zoom args))))
 
 module+ test
   (define first-sym->str
-    (transformer-lens first-lens symbol->string-lens))
+    (lens-zoom first-lens symbol->string-lens))
   (check-equal? (lens-view first-sym->str '(a b c))
                 '("a" b c))
   (check-equal? (lens-set first-sym->str '(a b c) '("a" b c))
@@ -60,7 +60,7 @@ module+ test
   (check-equal? (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
                 '("z" bee sea))
   (define trans-second-first/third-second
-    (transformer-lens* second-lens first-lens third-lens second-lens))
+    (lens-zoom* second-lens first-lens third-lens second-lens))
   (check-equal? (lens-view trans-second-first/third-second '(1 (2 3) (4 5)))
                 '(1 2 5))
   (check-equal? (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(1 2 5))
@@ -73,7 +73,7 @@ module+ test
                            (lens-set trans-second-first/third-second '(1 (2 3) (4 5)) '(a b c)))
                 '(a b c))
   (define (rekey-alist-lens key->new-key-lens)
-    (mapper-lens (transformer-lens car-lens key->new-key-lens)))
+    (mapper-lens (lens-zoom car-lens key->new-key-lens)))
   (check-equal? (lens-view (rekey-alist-lens symbol->string-lens) '((a . 1) (b . 2) (c . 3)))
                 '(("a" . 1) ("b" . 2) ("c" . 3)))
   (check-equal? (lens-set (rekey-alist-lens symbol->string-lens)
@@ -85,7 +85,7 @@ module+ test
                           '(("one" . 10) ("two" . 200) ("three" . 3000)))
                 '((one . 10) (two . 200) (three . 3000)))
   (define (rek+v-alist-lens key->new-key-lens value->new-value-lens)
-    (mapper-lens (transformer-lens* car-lens key->new-key-lens cdr-lens value->new-value-lens)))
+    (mapper-lens (lens-zoom* car-lens key->new-key-lens cdr-lens value->new-value-lens)))
   (check-equal? (lens-view (rek+v-alist-lens symbol->string-lens number->string-lens)
                            '((a . 1) (b . 2) (c . 3)))
                 '(("a" . "1") ("b" . "2") ("c" . "3")))
diff --git a/unstable/lens/transformer.scrbl b/unstable/lens/zoom.scrbl
similarity index 62%
rename from unstable/lens/transformer.scrbl
rename to unstable/lens/zoom.scrbl
index c47df3a..881007e 100644
--- a/unstable/lens/transformer.scrbl
+++ b/unstable/lens/zoom.scrbl
@@ -4,19 +4,19 @@
 
 @title{Lenses that transform subpieces}
 
-@defmodule[unstable/lens/transformer]
+@defmodule[unstable/lens/zoom]
 
-@defproc[(transformer-lens [lens lens?] [transform-lens lens?]) lens?]{
-Creates a lens that transforms the subpiece of the target that @racket[lens]
+@defproc[(lens-zoom [zoom-lens lens?] [transform-lens lens?]) lens?]{
+Creates a lens that transforms the subpiece of the target that @racket[zoom-lens]
 views with @racket[transform-lens].
 
-@racketblock[(lens-view (transformer-lens lens transform-lens) target)]
+@racketblock[(lens-view (lens-zoom zoom-lens transform-lens) target)]
 is equivalent to:
-@racketblock[(lens-transform lens target (λ (v) (lens-view transform-lens v)))]
+@racketblock[(lens-transform zoom-lens target (λ (v) (lens-view transform-lens v)))]
 
 @lens-unstable-examples[
   (define first-sym->str
-    (transformer-lens first-lens symbol->string-lens))
+    (lens-zoom first-lens symbol->string-lens))
   (lens-view first-sym->str '(a b c))
   (lens-set first-sym->str '(a b c) '("a" b c))
   (lens-set first-sym->str '(a b c) '("z" b c))
@@ -24,13 +24,13 @@ is equivalent to:
   (lens-view first-sym->str (lens-set first-sym->str '(a b c) '("z" bee sea)))
 ]}
 
-@defproc[(transformer-lens* [lens lens?] [transform-lens lens?] ... ...) lens?]{
-A multi-arg version of @racket[transformer-lens], analogous to
+@defproc[(lens-zoom* [zoom-lens lens?] [transform-lens lens?] ... ...) lens?]{
+A multi-arg version of @racket[lens-zoom], analogous to
 @racket[lens-transform/list]. It is equivalent to
-@racket[(lens-thrush (transformer-lens lens transform-lens) ...)].
+@racket[(lens-thrush (lens-zoom zoom-lens transform-lens) ...)].
 @lens-unstable-examples[
   (define first-sym->str/second-num->str
-    (transformer-lens* first-lens symbol->string-lens second-lens number->string-lens))
+    (lens-zoom* first-lens symbol->string-lens second-lens number->string-lens))
   (lens-view first-sym->str/second-num->str '(a 2 c))
   (lens-set first-sym->str/second-num->str '(a 2 c) '("a" "2" c))
   (lens-set first-sym->str/second-num->str '(a 2 c) '("z" "3" c))

From da77504a7636a00411440084f2a10e95a527765b Mon Sep 17 00:00:00 2001
From: AlexKnauth <alexander@knauth.org>
Date: Fri, 4 Sep 2015 23:33:40 -0400
Subject: [PATCH 5/5] add contracts for lens-zoom and lens-zoom*

---
 unstable/lens/zoom.rkt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/unstable/lens/zoom.rkt b/unstable/lens/zoom.rkt
index 996843c..eb21f17 100644
--- a/unstable/lens/zoom.rkt
+++ b/unstable/lens/zoom.rkt
@@ -1,11 +1,15 @@
 #lang sweet-exp racket/base
 
-provide lens-zoom
-        lens-zoom*
+require racket/contract/base
+provide
+  contract-out
+    lens-zoom (-> lens? lens? lens?)
+    lens-zoom* (->* [] #:rest (listof2 lens? lens?) lens?)
 
 require fancy-app
         lens/private/base/main
         lens/private/compound/thrush
+        lens/private/util/list-pair-contract
         racket/match
         unstable/sequence
         "isomorphism/base.rkt"