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28 lines
770 B
28 lines
770 B
3 years ago
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Exercise 4.71: Louis Reasoner wonders why the
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simple-query and disjoin procedures (4.4.4.2) are
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implemented using explicit delay operations, rather than being defined
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as follows:
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(define (simple-query
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query-pattern frame-stream)
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(stream-flatmap
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(lambda (frame)
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(stream-append
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(find-assertions query-pattern frame)
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(apply-rules query-pattern frame)))
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frame-stream))
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(define (disjoin disjuncts frame-stream)
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(if (empty-disjunction? disjuncts)
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the-empty-stream
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(interleave
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(qeval (first-disjunct disjuncts)
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frame-stream)
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(disjoin (rest-disjuncts disjuncts)
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frame-stream))))
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Can you give examples of queries where these simpler definitions would lead to
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undesirable behavior?
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