Re: How to pass STL containers (say a vector) ?
Roland Pibinger skrev:
On Fri, 19 May 2006 06:38:32 -0400, Sanjay Kumar
<nospam-hypertree@yahoo.com> wrote:
How do pyou ass a STL container
like say a vector or a map (to and from a function) ?
If you obey to the STL value-semantics dogma you pass everything by
value. If not you use the most efficient way.
The STL dogma is not to pass everything by value. Passing by const
reference is the norm for anything "heavy". What is standard is to
return by value rather than by some output parameter.
[snip]
For it to work, there has to be deep copy of the result of vector inside
function (myvector) into the "result" vector before myvector is destroyed.
Is that how it works ? Could this be inefficient if there is large amount
of data to be copied from the container ?
Yes, it can be inefficient. See also
http://groups.google.com/group/comp.lang.c++.moderated/browse_frm/thread/aa4daafacd01ce26
especially the subthread that starts with John Potters reply and which
also covers performance aspects.
That thread did NOT demonstrate that return by value is expensive. On
the contrary it did show that it was slightly faster than the
alternative methods.
Best wishes,
Roland Pibinger
Kind regards
Peter
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