On 04/15/2014 07:29 PM, Asumu Takikawa wrote:
On 2014-04-15 18:13:31 -0400, claire alvis wrote:
The push below includes changes to letrec expressions, internal
definitions, units, classes, and certain ill-formed shared expressions so
that they no longer leak the `undefined' value.
This is great! (especially happy that TR, even with classes, doesn't
have to worry about #<undefined> anymore)
Does TR not having to worry about #<undefined> mean that the following
program will typecheck?
#lang typed/racket
(define-type (Lazy-Listof A) (Promise (Pair A (Lazy-Listof A))))
(let ()
(define: lazy-zeros : (Lazy-Listof Zero)
(delay (cons 0 lazy-zeros)))
lazy-zeros)
Currently, `lazy-zeros' has the type (U Undefined (Lazy-Listof A))
within its definition, but only because it's in an internal definition
context. This has come up in a few different guises while I've
programmed in TR.
BTW, I was happy to see that the type `Lazy-Listof' could be defined
like that when coming up with the example.
Neil ⊥
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