RE: [Dev-C++] 'extern const' and std::vector

[Ioannis V. <iv...@at...>]

-----Original Message-----
From: dev...@li...
[mailto:dev...@li...] On Behalf Of David =
McKen
Sent: Thursday, May 01, 2003 4:10 PM
To: dev...@li...
Subject: [Dev-C++] 'extern const' and std::vector



My first question concerns the extern keyword.
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If I have a varible in one file (it is not a constant) but that varible
needs to accessed from the functions in another file. However these =
other
functions do not need (actually I don't want them to have) write access =
to
this variable, can I do something similar to 'const <var_type> =
<var_name>?'.
For those of you who are wondering why I don;t just try it myself I =
would
like to know what EVERY ANSI compatible compiler will do. The program I =
am
writing must remain portable.
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You do not specify language. That creates extra pain. In C & C++ yes you =
can
do extern const int x; In C++ you have better use a namespace.
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My other question concerns the std::vector container class of the STD.
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As far as I have seen the std:vector class stores it's contents =
contiguously
in memory (just like an array). Does this make vector classes reach =
their
maximum size once there is no block of memory big enough to hold it's =
data?=20
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You haven't to worry about these details. It is an implementation worry =
and
in reality the vector is just a handler interface. That's why the
vector::swap()  works instantly. Also you can specify for it your own =
memory
allocator. But handlers and allocators are advanced magic for me yet so =
i
can't tell you more on that till i end TC++PL3. :)
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In any case you have not to worry about these details.
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  I plan to use this class to act as the index for world system with up =
to
2^32 rooms in it (even if I store only pointers to each structure it =
still
gets pretty big). Would any of the other containers be better suited to =
this
purpose? I chose the vector bacause of it's speed (4 billion possible =
rooms,
gonna need the speed). The requirements for the container is to allow =
for a
numbering system for eah of the rooms with rooms being grouped within
ranges.=20

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Regarding constant random access with [] time cost: vector, deque, =
string,
valarray and bitset have this.
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Reference for all the time costs for all containers for all types of =
access
([], front operations, etc):
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"The C++ Programming Language" 3rd Edition or Special Edition by Bjarne
Stroustrup (the creator of C++):
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On page 464.
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Ioannis Vranos

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