Re: [Boost-bugs] [Boost C++ Libraries] #4410: Sparse/Packed matrix assignment needs type conversion

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #4410: Sparse/Packed matrix assignment needs type conversion
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-07-08 15:02:39

#4410: Sparse/Packed matrix assignment needs type conversion
--------------------------------------------------------+-------------------
  Reporter:  Marco Guazzone <marco.guazzone@…>          |       Owner:  guwi17 
      Type:  Patches                                    |      Status:  new    
 Milestone:  To Be Determined                           |   Component:  uBLAS  
   Version:  Boost Development Trunk                    |    Severity:  Problem
Resolution:                                             |    Keywords:         
--------------------------------------------------------+-------------------

Comment (by Marco Guazzone <marco.guazzone@…>):

 I propose a possible patch (see attachment: ''matrix_assign-
 packed_sparse_storage-type_conversion.patch'').

 Essentially,

 1. Expressions of the first type might be changed by casting an
 `E::value_type` to a `M::value_type`, like in this way:
 {{{#!c++
   if (static_cast<value_type>(v) != value_type/*zero*/())
 }}}
 Obviously, this does not work when `E::value_type` and `M::value_type` are
 not ''castable'' (e.g., `std::complex` and `double`, respectively).

 2. Expressions of the second type might be changed in 2 ways:
 * Option A (the one used in the proposed patch)
 {{{#!c++
   typedef typename matrix_traits<E>::value_type expr_value_type;
   functor_type::apply(*it, expr_value_type/*zero*/()); // NOTE: use of
 E::value_type in place of M::value_type
 }}}

 * Option B
 {{{#!c++
   typedef F<typename M::..., value_type> functor_type; // NOTE: use
 M::value_type instead of E::value_type
   functor_type::apply(*it, value_type/*zero*/()); // unchanged
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4410#comment:1>
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