13 lines
324 B
Racket
13 lines
324 B
Racket
#lang racket/base
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(require racket/promise
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(for-syntax racket/base))
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(provide define-on-demand)
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(define-syntax-rule (define-on-demand id rhs)
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(begin
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(define val (delay rhs))
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(define-syntax (id stx)
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(if (identifier? stx)
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#'(force val)
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(raise-syntax-error #f "bad syntax" stx)))))
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