on Thu Apr 05 2007, Michael Lacher <michael.lacher-AT-hlw.co.at> wrote:
David Abrahams wrote:
on Mon Apr 02 2007, "Eric Lemings" <lemings-AT-roguewave.com> wrote:
Expression templates sound very interesting. Could you give a quick summary or a link perhaps?
This is the canonical source:
http://osl.iu.edu/~tveldhui/papers/Expression-Templates/exprtmpl.html
Hmm, isnt that just boost::lambda?
Umm, no. Boost.Lambda is just _that_ :) Todd's work is the original and everything else followed.
I haven't used boost::lambda much yet, and i am not really proficient in functional programmign either, but could not the example form the page above:
int main() { DExpr<DExprIdentity> x; // Placeholder evaluate(x/(1.0+x), 0.0, 10.0); return 0; }
be written in boost:lambda as follows ?
int main() { evaluate(_1/(1.0+_1), 0.0, 10.0); return 0; }
If yes, what exactly can expression templates do that boost lambda cannot ?
Anything you like :) Read the section on optimizing vector expressions, for example. Then see http://www.oonumerics.org/blitz/ Boost.Lambda is just one example of the use of expression templates: in a library for generating anonymous function objects. Boost.Spirit is an example of the use of expression templates in a library for generating parsers. Boost.Xpressive is an example of the use of expression templates in a library for building regular expression matchers. Boost.Proto is a library that abstracts out a great deal of the hard work the authors of those other libraries have to do. It is a library for building libraries that rely on expression templates. HTH, -- Dave Abrahams Boost Consulting www.boost-consulting.com Don't Miss BoostCon 2007! ==> http://www.boostcon.com