id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12447	Need some help with a lambda expression exercize	JUAN DENT <juandent@…>	Aleksey Gurtovoy	"Hi,
I am studying ""C++ Template Metaprogramming"" and stuck in 
exercise 3-6 which states:

""Build a lambda expression that has functionality equivalent to 'twice'. 
Hint: mpl::apply is a metafunction!""

Now twice is defined like so:
{{{
#!C++
template<class F, class X>
struct twice
: mpl::apply< F, typename mpl::apply<F,X>::type>
{};
}}}

The book defines a lambda expression as: ""callable metadata. they have 2 
basic forms: metafunction classes and placeholder expressions"".

Thank you for your help!
Juan"	Support Requests	closed	To Be Determined	mpl	Boost 1.61.0	Problem	invalid