[Boost-users] Re: Lambda question

Anders Sundman writes:

Hi all!

I'm using the lambda library to compute the sum of squared differences, but I have encountered a puzzling problem. I would really appreciate if someone could explain it to me.

This doesn't compile:

std::inner_product(i1, i1+x, i2, 0.0, (_1 + _2), (_1*_1)(_1 - _2));

however, this does:

std::inner_product(i1, i1+x, i2, 0.0, std::plus<double>(), (_1*_1)(_1 - _2)); ^^^^^^^^ ^

Doesn't seem right. Do you really mean to invoke the function call operator on the result of _1*_1 ?? -- Dave Abrahams Boost Consulting www.boost-consulting.com