[Boost-users] Re: Boost::bind and protect

From: Miro Jurisic (macdev_at_[hidden])
Date: 2004-04-07 00:37:17

In article <c4vs8b$sv$1_at_[hidden]>,
 "Edward Diener" <eddielee_at_[hidden]> wrote:

> I am lost, even after looking at the code, of what protect is supposed to do
> in combination with boost::bind. 

An example where you need to use protect is when you want to call bind and pass 
the result of a bind to one of its arguments:

function<...>     f1 = bind(foo, ...);
function<...>     f2 = bind(bar, ..., f1, ...);

The reason for this is that when the result of bind #1 is passed to bind #2, 
then #1 is evaluated immediately, i.e., foo() is called not from inside bar() as 
you might desire, but on the second line above where bind is called. However, if 
you instead call

function<...>     f2 = bind(bar, ..., protect(f1), ...);

then the call to foo() is deferred until the body of bar().

hth

meeroh

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