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22 lines
884 B
22 lines
884 B
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Exercise 4.4: Recall the definitions of the
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special forms and and or from Chapter 1:
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and: The expressions are evaluated from left to right. If any
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expression evaluates to false, false is returned; any remaining expressions are
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not evaluated. If all the expressions evaluate to true values, the value of
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the last expression is returned. If there are no expressions then true is
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returned.
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or: The expressions are evaluated from left to right. If any expression
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evaluates to a true value, that value is returned; any remaining expressions
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are not evaluated. If all expressions evaluate to false, or if there are no
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expressions, then false is returned.
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Install and and or as new special forms for the evaluator by
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defining appropriate syntax procedures and evaluation procedures
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eval-and and eval-or. Alternatively, show how to implement
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and and or as derived expressions.
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