no TR support for streams?

[John Clements]

Perhaps I just don’t know how to search the racket docs correctly, but IIUC there’s no support for Streams in the current TR implementation? I just want to use stream-cons, empty-stream, stream-first, and stream-rest. I guess the easy workaround is just to use thunks to roll my own stream, but I’m wondering if I’m missing something obvious?

John

[Alex Knauth]

On Sep 6, 2019, at 1:04 PM, 'John Clements' via Racket Users <racket...@googlegroups.com> wrote:

Perhaps I just don’t know how to search the racket docs correctly, but IIUC there’s no support for Streams in the current TR implementation? I just want to use stream-cons, empty-stream, stream-first, and stream-rest. I guess the easy workaround is just to use thunks to roll my own stream, but I’m wondering if I’m missing something obvious?

You can wrap `stream-cons`, etc. in contracts and keep the original stream data type, but it's trickier than wrapping a normal function, and involves:

 - an untyped file which imports the macros and exports "function-ized" versions of the macros

 - a typed file which imports those function-ized things with require/typed, then exports new versions of the macros in terms of the functions

And looks something like like these two files:

; untyped-stream-function-ized.rkt

#lang racket

(provide stream-cons/fn)

(require racket/stream)

(define (stream-cons/fn a b)

  (stream-cons (a) (b)))

; typed-stream.rkt

#lang typed/racket

(provide stream-cons)

(require/typed "untyped-stream-function-ized.rkt"

  [stream-cons/fn (All (a) (-> (-> a) (-> (Sequenceof a)) (Sequenceof a)))])

(define-simple-macro (stream-cons a b)

  (stream-cons/fn (thunk a) (thunk b)))

This is the strategy I used for my `typed-racket-stream` repository:

https://github.com/AlexKnauth/typed-racket-stream

I wanted to do this instead of "rolling my own" stream library because I wanted to be able to share the same stream data-structure as existing untyped racket files.

Alex Knauth

[John Clements]

Oh! and in fact, you already bundled it as a pkg: https://pkgs.racket-lang.org/package/typed-racket-stream

Thanks!

John

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