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25 lines
1,008 B
Text
25 lines
1,008 B
Text
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(define-module (srfi 39)
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(export make-parameter parameterize)
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(import-immutable (scheme))
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(body
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(define (make-parameter value . o)
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(if (pair? o)
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(let ((converter (car o)))
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(lambda args
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(if (null? args)
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value
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(set! value (converter (car args))))))
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(lambda args (if (null? args) value (set! value (car args))))))
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(define-syntax parameterize
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(syntax-rules ()
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((parameterize ("step") ((param value tmp1 tmp2) ...) () body)
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(let ((tmp1 value) ...)
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(let ((tmp2 (param)) ...)
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(dynamic-wind (lambda () (param tmp1) ...)
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(lambda () . body)
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(lambda () (param tmp2) ...)))))
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((parameterize ("step") args ((param value) . rest) body)
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(parameterize ("step") ((param value tmp1 tmp2) . args) rest body))
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((parameterize ((param value) ...) . body)
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(parameterize ("step") () ((param value) ...) body))))))
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