On Sunday, 23 March 2014 at 17:38:17 UTC, Sean Kelly wrote:
On Saturday, 22 March 2014 at 14:04:01 UTC, Daniel Davidson
wrote:
For example, I could see technical reasons why in certain
non-quant areas like XML parsing where D can be faster than
C++.
(http://dotnot.org/blog/archives/2008/03/12/why-is-dtango-so-fast-at-parsing-xml/)
But then, with a large amount of time and unlimited funding
the techniques could probably be duplicated in C++.
Try no funding and a trivial amount of time. The JSON parser I
wrote for work in C performs zero allocations and unescaping is
performed on demand. D arguably makes this easier by building
slicing into the language, but not decoding or copying is a
design decision, not a language artifact (at least in the case
of C/C++ where aliasing data is allowed). The take-away from
that Tango article is that the performance hit for parsing is
aggressively decoding data the user may not care about or may
not want decoded in the first place. This just happens to be
the approach that basically every XML parser on the planet uses
for some ridiculous reason.
This isn't for ridiculous reasons, this is because in other
languages you have no guarantee that what you work on is
immutable. So you must aggressively copy anyway. With a separate
decoding step, you'll ends up copying twice, which is also
wasteful.
