add mapper-lens

unstable/lens/mapper.rkt

@@ -0,0 +1,30 @@
+#lang racket/base
+
+(provide mapper-lens
+         )
+
+(require lens/base/main
+         fancy-app
+         )
+(module+ test
+  (require rackunit lens/list/main))
+
+(define (mapper-lens lens)
+  (make-lens
+   (lens-view/map lens _)
+   (lens-set/map lens _ _)))
+
+(define (lens-view/map lens tgts)
+  (map (lens-view lens _) tgts))
+
+(define (lens-set/map lens tgts new-views)
+  (map (lens-set lens _ _) tgts new-views))
+
+(module+ test
+  (check-equal? (lens-view (mapper-lens first-lens) '((a b) (c d) (e f)))
+                '(a c e))
+  (check-equal? (lens-set (mapper-lens first-lens) '((a b) (c d) (e f)) '(1 2 3))
+                '((1 b) (2 d) (3 f)))
+  (check-equal? (lens-transform (mapper-lens first-lens) '((a b) (c d) (e f)) (map symbol->string _))
+                '(("a" b) ("c" d) ("e" f)))
+  )