Hello Tom,

-----Original Message----- From: tom gee [mailto:rockonedge@gmail.com] Subject: [Boost-users] A question about boost::lambda::if_ behavior

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Can anyone please explain this code:

[snip]

The problem is that the expression std::cout << constant("Bingo:<") is evaluated immediately. Why? Because it's not a lambda expression. You have two options that will help you turn your if-branch into a lambda expression; either use boost::lambda::var or boost::lambda::constant.

Using boost::lambda::var:

std::for_each(setFinalVal.begin(),setFinalVal.end(), (std::cout << _1 << " ", if_(_1 < 24.000001 && _1 > 23.999999) [var(std::cout) << "Bingo:<" << _1 << ">"]));

Using boost::lambda::constant:

std::for_each(setFinalVal.begin(),setFinalVal.end(), (std::cout << _1 << " ", if_(_1 < 24.000001 && _1 > 23.999999) [std::cout << constant("Bingo:<") << _1 << ">"]));

Cheers, Bjorn Karlsson constant should be better (lower overhead, conceptually closer), but no biggy. I beleive this is the No.1 FAQ, is it not? (PS: why does not the lambda docs say in the function call overload

Bjorn.Karlsson@readsoft.com wrote: section to use BLL's bind? It took me AGES to figure out how to do that!)