🚀 go-pugleaf

Nathan Myers <ncm@netcom.com> writes:
>>>....  The feeling in the committee was that that would be too close to
>>>vector<>.  I.e. when you think you want an auto_array_ptr, consider using
>>>a vector<> instead.  

John Max Skaller <maxtal@suphys.physics.su.oz.au> writes:
>>In my humble opinion, this is a mistake; vector<> is a far bigger chunk of
>>code than auto_array_ptr<> and supports functionality beyond what a natural
>>auto_array_ptr would supply.

jbuck@Synopsys.COM (Joe Buck) wrote:
>Actually, this need not be the case. If you _use_ a vector
>"as if" it were a less kind of array type, the code
>for the "extra" functionality won't be generated.

Rather, *some* of the code won't be generated.  In practice, you're
getting code and data you don't need, that slows down compilation
and occupies memory, because vectors must support the push_back
functionality (they need to grow).  auto_array_ptr<>, on the other
hand, doesn't impose such costs.

>Remember vector isn't really a template, it's a built in 
>structuring tool of the C++ language just like 
>"array" or "struct" is.

I'm not buying it, John.  That's just like saying stdio.h isn't really a
header file, since it's standard and C implementations could do various
kinds of magic when they see the string '#include <stdio.h>'.  But in
practice we still get compilers that work in the natural way.  And in
practice, vector is going to be a template for the next several years at
least.

>Don't expect this kind of optimisation right away -- 
>we need stable working ISO C++ implementations first.

Don't expect this kind of optimization for many years to come.
In any case, I'd advise against it: special-casing STL for improved
performance would mean templates stay inefficient.

-- 
-- Joe Buck 	<jbuck@synopsys.com>	(not speaking for Synopsys, Inc)


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