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We
overload the << and >> operators for insertion into the
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output
stream and extraction from the input stream.
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The
iostream library overloads these operators for the
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built-in
data types, but is not equipped to handle new data
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types
that we create. Therefore, in order for extraction and
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insertion
operators to be used with objects of our classes,
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we
must overload these operators ourselves.
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The
extraction and insertion operators must be overloaded
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as
non-members because the first operand is an object of
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type
istream or ostream and not an object of one of our
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classes.
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