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12 lines
685 B
12 lines
685 B
2 years ago
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Exercise 4.77: In 4.4.3 we saw
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that not and lisp-value can cause the query language to give
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“wrong” answers if these filtering operations are applied to frames in which
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variables are unbound. Devise a way to fix this shortcoming. One idea is to
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perform the filtering in a “delayed” manner by appending to the frame a
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“promise” to filter that is fulfilled only when enough variables have been
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bound to make the operation possible. We could wait to perform filtering until
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all other operations have been performed. However, for efficiency’s sake, we
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would like to perform filtering as soon as possible so as to cut down on the
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number of intermediate frames generated.
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