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32 lines
828 B
32 lines
828 B
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Exercise 2.22: Louis Reasoner tries to rewrite
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the first square-list procedure of Exercise 2.21 so that it
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evolves an iterative process:
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(define (square-list items)
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(define (iter things answer)
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(if (null? things)
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answer
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(iter (cdr things)
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(cons (square (car things))
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answer))))
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(iter items nil))
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Unfortunately, defining square-list this way produces the answer list in
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the reverse order of the one desired. Why?
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Louis then tries to fix his bug by interchanging the arguments to cons:
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(define (square-list items)
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(define (iter things answer)
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(if (null? things)
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answer
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(iter (cdr things)
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(cons answer
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(square
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(car things))))))
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(iter items nil))
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This doesn’t work either. Explain.
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