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15 lines
840 B
15 lines
840 B
2 years ago
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Exercise 2.78: The internal procedures in the
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scheme-number package are essentially nothing more than calls to the
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primitive procedures +, -, etc. It was not possible to use the
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primitives of the language directly because our type-tag system requires that
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each data object have a type attached to it. In fact, however, all Lisp
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implementations do have a type system, which they use internally. Primitive
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predicates such as symbol? and number? determine whether data
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objects have particular types. Modify the definitions of type-tag,
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contents, and attach-tag from 2.4.2 so that our
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generic system takes advantage of Scheme’s internal type system. That is to
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say, the system should work as before except that ordinary numbers should be
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represented simply as Scheme numbers rather than as pairs whose car is
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the symbol scheme-number.
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