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26 lines
760 B
26 lines
760 B
2 years ago
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Exercise 4.8: “Named let” is a variant
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of let that has the form
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(let ⟨var⟩ ⟨bindings⟩ ⟨body⟩)
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The ⟨bindings⟩ and ⟨body⟩ are just as in ordinary let,
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except that ⟨var⟩ is bound within ⟨body⟩ to a procedure whose body
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is ⟨body⟩ and whose parameters are the variables in the ⟨bindings⟩.
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Thus, one can repeatedly execute the ⟨body⟩ by invoking the procedure
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named ⟨var⟩. For example, the iterative Fibonacci procedure
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(1.2.2) can be rewritten using named let as follows:
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(define (fib n)
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(let fib-iter ((a 1) (b 0) (count n))
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(if (= count 0)
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b
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(fib-iter (+ a b)
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a
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(- count 1)))))
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Modify let->combination of Exercise 4.6 to also support named
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let.
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