From 94a13eccaaa5dd13e73992b3b3f0707def8423b1 Mon Sep 17 00:00:00 2001
From: Jack Firth <jackhfirth@gmail.com>
Date: Wed, 8 Jul 2015 10:06:39 -0700
Subject: [PATCH] Add set* and transform* contracts

---
 lens/base/transform.rkt     | 10 ++++++----
 lens/base/view-set.rkt      | 10 ++++++----
 lens/list-pair-contract.rkt | 10 ++++++++++
 3 files changed, 22 insertions(+), 8 deletions(-)
 create mode 100644 lens/list-pair-contract.rkt

diff --git a/lens/base/transform.rkt b/lens/base/transform.rkt
index 7909070..1b4fd34 100644
--- a/lens/base/transform.rkt
+++ b/lens/base/transform.rkt
@@ -1,16 +1,18 @@
 #lang racket
 
 (require unstable/sequence
-         "base.rkt")
+         "base.rkt"
+         "../list-pair-contract.rkt")
 
 (module+ test
   (require rackunit
            fancy-app))
 
 (provide
- lens-transform*
- (contract-out [lens-transform (-> lens? any/c (-> any/c any/c) any/c)]))
-               
+ (contract-out
+  [lens-transform (-> lens? any/c (-> any/c any/c) any/c)]
+  [lens-transform* (->* (any/c) #:rest (listof2 lens? (-> any/c any/c)) any/c)]))
+
 
 
 (define (listof* . contracts)
diff --git a/lens/base/view-set.rkt b/lens/base/view-set.rkt
index c58b1e5..c63424b 100644
--- a/lens/base/view-set.rkt
+++ b/lens/base/view-set.rkt
@@ -2,15 +2,17 @@
 
 (require unstable/sequence
          fancy-app
-         "base.rkt")
+         "base.rkt"
+         "../list-pair-contract.rkt")
+
 (module+ test
   (require rackunit))
 
 (provide
- lens-set*
  (contract-out [lens-view (-> lens? any/c any/c)]
-               [lens-view* (->* [any/c] #:rest (listof lens?) any/c)]
-               [lens-set (-> lens? any/c any/c any/c)]))
+               [lens-view* (->* (any/c) #:rest (listof lens?) any/c)]
+               [lens-set (-> lens? any/c any/c any/c)]
+               [lens-set* (->* (any/c) #:rest (listof2 lens? any/c) any/c)]))
 
 
 (define (lens-view lens v)
diff --git a/lens/list-pair-contract.rkt b/lens/list-pair-contract.rkt
new file mode 100644
index 0000000..411a3e3
--- /dev/null
+++ b/lens/list-pair-contract.rkt
@@ -0,0 +1,10 @@
+#lang racket
+
+(provide
+ (contract-out [listof2 (-> contract? contract? contract?)]))
+
+
+(define (listof2 first-val/c second-val/c)
+  (define c
+    (or/c empty? (cons/c first-val/c (cons/c second-val/c (recursive-contract c)))))
+  c)