add sublist-lens

unstable/lens/sublist.rkt

@@ -0,0 +1,19 @@
+#lang racket/base
+
+(provide sublist-lens)
+
+(require lens/base/main
+         lens/list/main
+         )
+(module+ test
+  (require rackunit))
+
+(define (sublist-lens i j)
+  (lens-thrush (take-lens j) (drop-lens i)))
+
+(module+ test
+  (check-equal? (lens-view (sublist-lens 1 4) '(0 1 2 3 4 5))
+                '(1 2 3))
+  (check-equal? (lens-set (sublist-lens 1 4) '(0 1 2 3 4 5) '(a b c))
+                '(0 a b c 4 5))
+  )