add documentation for struct-lens

lenses/deflenses.rkt

@@ -1,7 +1,7 @@
 #lang racket
 
 (require scribble/manual
-         "main.rkt")
+         (for-label lenses))
 
 (provide deflens
          deflenses)

lenses/info.rkt

@@ -1,4 +1,4 @@
 #lang info
 
 (define name "lenses")
-(define scribblings '(("main.scrbl" () () "lenses")))
+(define scribblings '(("main.scrbl" () (library) "lenses")))

lenses/main.scrbl

@@ -15,5 +15,6 @@ source code: @url["https://github.com/jackfirth/lenses"]
 
 @include-section["core/main.scrbl"]
 @include-section["list/main.scrbl"]
+@include-section["struct-lens.scrbl"]
 @include-section["syntax.scrbl"]
 @include-section["applicable.scrbl"]

lenses/struct-lens.scrbl

@@ -0,0 +1,24 @@
+#lang scribble/manual
+
+@(require scribble/eval
+          "lenses-examples.rkt"
+          (for-label lenses
+                     lenses/struct-lens
+                     racket/base
+                     racket/contract))
+
+
+@title{Struct lenses}
+
+@defmodule[lenses/struct-lens]
+
+@defform[(struct-lens struct-id field-id)]{
+  Returns a lens for viewing the @racket[field-id] field of
+  a @racket[struct-id] instance.
+  @lenses-examples[
+    (require lenses/struct-lens)
+    (struct foo (a b c) #:transparent)
+    (lens-view (struct-lens foo a) (foo 1 2 3))
+    (lens-set (struct-lens foo a) (foo 1 2 3) 100)
+]}
+