Re: OT: std::vector to C array

[Eljay Love-Jensen <eljay at adobe dot com>]

Hi Sebastian,

Approach #1 is the correct way to convert a std::vector to a C array.

Approach #2 does not convert the std::vector to a C array.  It merely sets 
a pointer to the begin iterator in those cases where vector<T>::iterator is 
incidently identical to the pointer, and (I assume) causes a compiler error 
in other cases.

Approach #3 does not convert the std::vector to a C array.  It merely sets 
a pointer to the first element.  Note:  std::vector<> does NOT have a 
front() method, the std::queue<> does.  You should rather do something 
like:  a = &(*v.begin()); ... with the caveat that you are relying on your 
STL implementation to utilize consecutive memory.

I believe that the current ISO 14882 standard does NOT guarantee that a 
std::vector<> is necessarily in consecutive memory, so using a pointer to 
do C-style pointer/array access is not guaranteed to work.

However, all implementations of std::vector<> that I am aware of DO 
implement vector elements in consecutive memory.  (But my awareness is not 
omniscient.  *heh*)

Also, I believe that the working group for the future ISO 14882 standard is 
seriously considering the guarantee that std::vector<> (and likewise with 
std::string<>) is in consecutive memory locations.

Sincerely,
--Eljay