Hi Folks, I've got a question about supporting brace initialization
syntax.
double a[] { 1,2,3 };
ok, always has been.
boost::array b {{ 1,2,3 }}
Needs double braces because there's one member data to be initialized,
and we want to initialize that with {1,2,3}. Fine. Some compilers
let you drop one set of braces; GCC 4.4 does, but produces a warning.
Now, I make a class:
template Vector
{
public:
...
boost::array data;
};
Vector<3> v {{{1,2,3}}}
Still OK: again in principle, I need three sets of braces.
However, I'd like my Vector::data member to be private, but as soon as
I do that, Vector isn't a POD any more, and the brace initialization
no longer works. (I'm not sure if this is in line with the standard,
or is a GCC 4.4 limitation.)
No problem, std::initializer_list to the rescue:
template Vector
{
public:
Vector(std::initializer_list<double> i) : data{i} {}
...
private:
boost::array data;
};
Alas, boost::array has no constructor that takes an initializer_list:
error: no matching function for call to ‘boost::array::array(std::initializer_list<double>&)’
note: candidates are: boost::array::array(const
boost::array&)
/usr/local/Boost/1.44/boost/array.hpp:57:17: note:
boost::array::array()
scons: *** [fast/Test/testVector.o] Error 1
Having poked through the standard, I can't see any way to convince the
compiler to turn an initializer_list back into the semantic equivalent
of a brace initializer.
Does anyone know how to do this?
Does boost::array need a constructor that takes initializer_lists?
Thanks!
--
Dave Steffen, Ph.D. - Software Engineer
Numerica Corporation http://www.numerica.us
4850 Hahns Peak Drive, Suite 200
Loveland, Colorado 80538
main (970) 461-2000 x 227
Email: dave.steffen@numerica.us
fax (970) 461-2004
