63 lines
3.0 KiB
Racket
63 lines
3.0 KiB
Racket
#lang scribble/manual
|
|
@require[@for-label[typed-struct-props
|
|
racket/base]]
|
|
|
|
@title{Struct type properties for Typed/Racket}
|
|
@author[@author+email["Georges Dupéron" "georges.duperon@gmail.com"]]
|
|
|
|
@defmodule[typed-struct-props]
|
|
|
|
@defform[#:literals (: prop:custom-write )
|
|
(struct/props maybe-type-vars name ([field : type] ...) options ...)
|
|
#:grammar
|
|
[(maybe-type-vars (code:line)
|
|
(v ...))
|
|
(options #:transparent
|
|
(code:line #:property prop:custom-write custom-write)
|
|
(code:line #:equal+hash equal+hash))]
|
|
#:contracts ([custom-write
|
|
(∀ (v ...)
|
|
(→ (name v ...)
|
|
Output-Port
|
|
(U #t #f 0 1)
|
|
Any))]
|
|
[equal+hash
|
|
(List (∀ (v ... |v'| ...)
|
|
(→ (name v ...)
|
|
(name |v'| ...)
|
|
(→ Any Any Boolean)
|
|
Any))
|
|
(∀ (v ...)
|
|
(→ (name v ...)
|
|
(→ Any Integer)
|
|
Integer))
|
|
(∀ (v ...)
|
|
(→ (name v ...)
|
|
(→ Any Integer)
|
|
Integer)))])]{
|
|
This form defines a @racketmodname[typed/racket] struct type, and accepts a
|
|
small subset of @racketmodname[racket]'s struct type properties.
|
|
|
|
It implements these struct type properties in a type-safe manner: the current
|
|
implementation in @racketmodname[typed/racket] does not properly type-check
|
|
functions and values used as struct type properties. This library declares the
|
|
user-provided functions outside of the struct definition, with the type given
|
|
above (e.g.
|
|
@racket[(∀ (v ...) (→ (name v ...) Output-Port (U #t #f 0 1) Any))] for the
|
|
argument of the @racket[prop:custom-write] property), to ensure that these
|
|
functions and values are properly checked.
|
|
|
|
The API should (hopefully) stay backward-compatible when Typed/Racket
|
|
officially supports (or rejects) structure type properties. In other words:
|
|
@itemlist[
|
|
@item{If @racketmodname[typed/racket] eventually implements the same interface
|
|
as the one provided by this library, then we will update this library so
|
|
that it simply re-provide @racket[struct] renamed as @racket[struct/props].}
|
|
@item{If @racketmodname[typed/racket] eventually implements some type-safe
|
|
struct type properties, then we will update this library will so that it
|
|
translates back to @racketmodname[typed/racket]'s implementation, as much as
|
|
possible.}
|
|
@item{If @racketmodname[typed/racket] eventually disallows struct type
|
|
properties, then we will update this library so that it uses some
|
|
@racketmodname[typed/racket/unsafe] tricks to still make them available, if
|
|
it can be done.}]} |