Re: Why do we have to define a namespace with string header?
"Phlip" <phlipcpp@yahoo.com> wrote in message
news:lQd8g.3351$fb2.1187@newssvr27.news.prodigy.net...
bgeneto wrote:
Thanks for your explanation, if I understand well the string class and
possibly it's methods are defined in the namespace std within the
standard header <string>. If so, what is the point in doing this?
The general set of keywords for C++ were invented in the 1980s.
And many more were added during "standardization" in the 1990s.
And *lots* more library names (which are not keywords) were added
as well.
The Standard Library - the most common and most useful things to do /with/
those keywords - was ratified in 1997.
This was a good thing because the library had time to mature.
Some of it. And parts of it were paper tigers that were standardized
before they were ever implemented.
But the new language specification had to preserve over a decade of legacy
code. The language committees could not tell everyone, "some of your
functions will now disappear, some will change their behavior, and some
will break your programs now". People would simply reject Standard C++,
and keep using the "ARM C++" and its defacto standard.
But that's exactly what the C++ committee did do.
So the committee fixed this in one move by putting everything in The
Standard Library into one big namespace. Legacy code that did not declare
this namespace could continue to use their legacy libraries. You might
find your C++ implementation still contains files such as "iostream.h".
It's nice to think that the C++ committee wisely took a new departure
and made a point of staying out of the way of old library naming
practices, but this was not their goal in adding namespace std and
the new headers. It was the *vendors* who wisely retained the legacy
headers for many years.
(Worse, code can also mix-and-match legacy and standard code. The less
said about that the better.)
Maybe, but quite a lot *had* to be said about it, by those of us who had
to support customers through a decade of transition. You will *still*
see regular postings on these newsgroups along the lines of, "I included
<string>, so why isn't class string defined?"
So, if you need strings or "STL" containers, import their namespace. This
is a very minor detail of well-structured code.
I agree that importing the entire std namespace is often the best way
to repair the damage, but I'm in a tiny minority.
P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com