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32 lines
684 B
32 lines
684 B
2 years ago
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Exercise 3.52: Consider the sequence of
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expressions
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(define sum 0)
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(define (accum x)
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(set! sum (+ x sum))
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sum)
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(define seq
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(stream-map
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accum
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(stream-enumerate-interval 1 20)))
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(define y (stream-filter even? seq))
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(define z
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(stream-filter
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(lambda (x)
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(= (remainder x 5) 0)) seq))
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(stream-ref y 7)
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(display-stream z)
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What is the value of sum after each of the above expressions is
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evaluated? What is the printed response to evaluating the stream-ref
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and display-stream expressions? Would these responses differ if we had
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implemented (delay ⟨exp⟩) simply as (lambda () ⟨exp⟩)
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without using the optimization provided by memo-proc? Explain.
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