12211fff72
* A long-standing bug, which happened with
(let ([x (lazy (delay 1))]) (force x) (force x))
not being properly handled.
* Added `delay/strict', mostly for the below.
* Made srfi/45 reprovide it as `eager'.
* Also restricted the exports from srfi/45 to its interface.
All of these issues were reported by Andreas Rottmann.
17 lines
798 B
Racket
17 lines
798 B
Racket
#lang scheme/base
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;; scheme/promise has srfi-45-style primitives
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(require scheme/promise)
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(provide delay lazy force
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;; Strictly speaking, this should be a procedure according to srfi-45.
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;; It's easy to make it one, but then it loses its ability to deal
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;; with multiple values (which the srfi completely ignores).
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(rename-out [delay/strict eager]))
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;; TODO: there is a small difference between the primitives in srfi-45 and the
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;; ones provided by scheme/promise (the latter is a bit more permissive). See
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;; "library approach" in scheme/promise and see the post-finalization
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;; discussion on the srfi-45 list. I (Eli) showed at some point how the
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;; "language approach" primitives can be used to implement the other, and this
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;; needs to be done here too.
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