Re: could not deduce template argument for 'double [m][n]' from 'double [2][3]'

From:
=?windows-1252?Q?Daniel_Kr=FCgler?= <daniel.kruegler@googlemail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 5 Feb 2012 06:22:09 -0800 (PST)
Message-ID:
<jgloef$2dd$1@dont-email.me>
Am 05.02.2012 09:30, schrieb Helmut Zeisel:

On 1 Feb., 19:29, Helmut Jarausch<jarau...@igpm.rwth-aachen.de>
wrote:

I'd use the new std::array.


How can I initialize 2-dim std::array?

std::array<std::array<double,2>,2> a={{1,2},{3,4}};


Unfortunately you need one further pair of braces for each array level,
ending in

std::array<std::array<double,2>,2> a={{ {{1,2}}, {{3,4}} }};

This is so, because the simple initialization of std::array with a
single pair of braces relies on one very special rule of aggregate
initialization that allows elision of braces under a very restricted set
of circumstances. Technically you could satisfy this condition by
rewriting above to

std::array<std::array<double,2>,2> a={ std::array<double,2>{{1,2}},
std::array<double,2>{{3,4}} };

but this is obviously worse compared to the alternative mentioned above.

HTH & Greetings from Bremen,

Daniel Kr?gler

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