Header-saving hint for IOStreams

From: Daryle Walker (darylew_at_[hidden])
Date: 2000-10-02 22:37:43

I think this was inspired by something I saw in some Boost header.  (I wrote
this two months ago, so I forgot the specifics [and to send it, until now].)

Don't #include <iostream> unless you need cin, cout, and/or any of the other
standard stream objects.  If you just need the basic classes, #include
<istream> and/or <ostream> as appropriate.  The std::basic_iostream class
template happens to be defined in header <istream>, probably to avoid having
to #include <iostream> for it.

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