Re: inconsistencies when compiling
On Jan 30, 4:17 am, Jerry Coffin <jcof...@taeus.com> wrote:
In article <17657871-dabc-45ec-a04b-1dc6a6ea3f39
@v46g2000hsv.googlegroups.com>, james.ka...@gmail.com says...
Jerry Coffin wrote:
[...]
In practice, of course, transform and accumulate are probably
better choices most of the time. But there too: how far do you
push the idiom? My CRC, MD5 and SHA classes are "accumulators",
to be used with std::accumulate. Again, it was fun, and the
idiom looks cool, but is it really more readable? (There's also
the problem that the "accumulator" in std::accumulate gets
copied around an awful lot. In the case of CRC, that's not too
much of a problem---the accumulator may be a class type, but
it's only 16 or 32 bits in size. In the case of MD5 and the SHA
classes, however, it has a very noticeable impact on
performance---accumulating a single char is usually only a write
and an index manipulation, but you end up copying something like
48 bytes, twice.)
I've never written one of these this way, so I'm hard put to
say much concrete about them. I can certainly see where they
might be more of a problem than a solution.
The idiom for using them is very natural:
std::string md5
= std::accumulate( text.begin(), text.end(), MD5() ) ;
Or even:
text += std::accumulate( text.begin(), text.end(), MD5() ) ;
The problem is purely performance.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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