docs for unstable/prop-contract

collects/unstable/scribblings/prop-contract.scrbl

@@ -0,0 +1,52 @@
+#lang scribble/manual
+@(require scribble/struct
+          scribble/decode
+          scribble/eval
+	  "utils.rkt"
+          (for-label racket/base
+                     racket/contract
+                     unstable/prop-contract))
+
+@(define the-eval (make-base-eval))
+@(the-eval '(require racket/contract unstable/prop-contract))
+
+@title{Contracts for struct type properties}
+
+@defmodule[unstable/prop-contract]
+
+@unstable[@author+email["Ryan Culpepper" "ryanc@racket-lang.org"]]
+
+@defproc[(struct-type-property/c [value-contract contract?])
+         contract?]{
+
+Produces a contract for struct type properties. When the contract is
+applied to a struct type property, it produces a wrapped struct type
+property. When the wrapped struct type property is used to create a
+new struct type (via @racket[struct], @racket[make-struct-type], etc),
+it applies @racket[value-contract] to the value associated with the
+property.
+
+The contract has no effect on the struct type property accessor.
+
+@examples[#:eval the-eval
+(define-values (prop prop? prop-ref)
+  (make-struct-type-property 'prop))
+
+(define/contract wrapped
+    (struct-type-property/c (-> any/c (-> number? number?)))
+  prop)
+
+(struct s (f)
+  #:property wrapped (lambda (s) (s-f s)))
+
+(define (get-f s) ((prop-ref s) s))
+
+(define s1 (s add1))
+((get-f s1) 5)
+((get-f s1) 'apple)
+
+(define s2 (s (lambda (n) (if (zero? n) 'zero 'nonzero))))
+((get-f s2) 5)
+((get-f s2) 'apple)
+]
+}

collects/unstable/scribblings/unstable.scrbl

@@ -111,6 +111,7 @@ Keep documentation and tests up to date.
 @include-section["markparam.scrbl"]
 @include-section["debug.scrbl"]
 @include-section["wrapc.scrbl"]
+@include-section["prop-contract.scrbl"]
 
 @;{--------}