Re: [Boost-users] multi_array and variants

Hi Alle, 2010/11/9 Alle Meije Wink

Dear Kris, thanks for your reply.

You are welcome.

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template<typename T> class bisArray: public bisObject { typedef boost::variant < boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref, boost::multi_array_ref

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bisArray_t; bisArray_t _bisArray;

However what I am stuck with seems to be, in essence, still the same thing:

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/home/amwink/programs/cpp/bis/src/bisniftiimage.cpp||In function ‘void bis::bisReadNifti(std::string)’:| /home/amwink/programs/cpp/bis/src/bisniftiimage.cpp|102|warning: unused variable ‘testimage’| /usr/include/boost/variant/variant.hpp||In constructor ‘boost::variant::variant() [with T0_ = boost::multi_array_ref, T1 = boost::multi_array_ref, T2 = boost::multi_array_ref, T3 = boost::multi_array_ref, T4 = boost::multi_array_ref, T5 = boost::multi_array_ref, T6 = boost::multi_array_ref, T7 = boost::multi_array_ref, T8 = boost::multi_array_ref, T9 = boost::detail::variant::void_, T10 = boost::detail::variant::void_, T11 = boost::detail::variant::void_, T12 = boost::detail::variant::void_, T13 = boost::detail::variant::void_, T14 = boost::detail::variant::void_, T15 = boost::detail::variant::void_, T16 = boost::detail::variant::void_, T17 = boost::detail::variant::void_, T18 = boost::detail::variant::void_, T19 = boost::detail::variant::void_]’:| /home/amwink/programs/cpp/bis/src/bisarray.hpp|52|instantiated from ‘bis::bisArray<T>::bisArray(T*, size_t, std::vector) [with T = unsigned char]’| /home/amwink/programs/cpp/bis/src/bisimage.hpp|33|instantiated from ‘bis::bisImage<T>::bisImage(T*, size_t, std::vector) [with T = unsigned char]’| /home/amwink/programs/cpp/bis/src/bisniftiimage.cpp|126|instantiated from here| /usr/include/boost/variant/variant.hpp|1198|error: no matching function for call to ‘boost::multi_array_ref::multi_array_ref()’| /usr/include/boost/multi_array/multi_array_ref.hpp|623|note: candidates are: boost::multi_array_ref::multi_array_ref(T*, const typename boost::const_multi_array_ref::storage_order_type&, const typename boost::const_multi_array_ref::index*, const typename boost::const_multi_array_ref::size_type*) [with T = unsigned char, long unsigned int NumDims = 1ul]| /usr/include/boost/multi_array/multi_array_ref.hpp|469|note: boost::multi_array_ref::multi_array_ref(T*, const boost::detail::multi_array::extent_gen<NumDims>&, const boost::general_storage_order<NumDims>&) [with T = unsigned char, long unsigned int NumDims = 1ul]| /usr/include/boost/multi_array/multi_array_ref.hpp|463|note: boost::multi_array_ref::multi_array_ref(T*, const boost::detail::multi_array::extent_gen<NumDims>&) [with T = unsigned char, long unsigned int NumDims = 1ul]| /usr/include/boost/multi_array/multi_array_ref.hpp|417|note: boost::multi_array_ref::multi_array_ref(const boost::multi_array_ref&)| ||=== Build finished: 1 errors, 1 warnings ===|

So boost.variant now sugegsts that multi_array_ref() is called, a constructor with no arguments! I don't use that, and I don't even think it exists (because it produces a multi_array view of an *existing* C-style array!

The error sais, that the default constructor of multi_array_ref (which does not exist) is being called from the default constructor of variant. By default, variant cannot be empty. It's default constructor tries to use the default constructor of the first type on the list. Therefore You have two options: 1) Always initialize the variant with some array, 2) Add a type to the beginning of the list, which will stand for "no value": #include variant< none_t, [...] > bisArray; Any idea why a problem with the *default* constructor would turn up?

The default ctor of each member is called if You don't specify another means of initialization in the constructor. Regards, Kris