fcd4c4e38d
Add plt-responsible props. Add hash-union to unstable. Fix doc for compound-paragraph. Fix unstable/scribblings/util. svn: r16811
14 lines
314 B
Scheme
14 lines
314 B
Scheme
#lang scheme/base
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(provide hash-union)
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;; map map (key val val -> val) -> map
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(define (hash-union h1 h2 f)
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(for/fold ([h* h1])
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([(k v2) h2])
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(let* ([v1 (hash-ref h1 k #f)]
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[new-val (if v1
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(f k v1 v2)
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v2)])
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(hash-set h* k new-val))))
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