Re: printing in C++
On Saturday, March 16, 2013 5:46:30 PM UTC, =D6=F6 Tiib wrote:
On Saturday, 16 March 2013 18:47:14 UTC+2, James Kanze wrote:
No, you don't want to derive std::string from anything and
pay the penalty of virtual function access all over the
place. We already have stringstream which is full of
virtual functions and which is several times slower than
std::string when concatenating strings from pieces (yes I
have measured it), although this should be one of the main
usage cases for stringstreams.
Why should this be one of the main usage cases for stringstream?
One may use stringstream on case when str1 + str2 + str3 does
not work. For example when he needs to concatenate
information in dynamic array into string.
If str<n> are pointers, then it will work. If they aren't
pointers, then we're not speaking about concatenation.
The "abstraction" of istream and ostream is converting to and
from an external human readable format.
Modern times "human readable" text is used a lot in interfaces
... external or internal. With external interfaces the latency
and through-put of carrying media is the bottle-neck.
Efficiency of streaming does not matter there much.
stingstream is used more in internal interfaces. There media
is memory and bottle-neck is stringstream.
There's never any reason to use stringstream for internal
interfaces. You should be using struct. As long as the
interface is internal, there's no reason to format; both sides
understand the same internal representation.
I don't see where is should even occur to someone to use them for just
concatenation.
I trust that Paavo meant that concatenation is operation of stringstream
that it does a lot when used for anything.
I don't know what Paavo meant, but using stringstream for
concatenation is _not_ good practice.
--
James