<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Am Mi., 23. Jan. 2019 um 16:34 Uhr schrieb dariomt--- via ublas <<a href="mailto:ublas@lists.boost.org">ublas@lists.boost.org</a>>:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Hello,</div><div><br></div><div>Thanks but I already know about vector proxies, and I don't think covers my needs.</div></div></div></div></blockquote><div><br></div><div>True because all proxies constructors require container types.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><br></div><div>Let me rephrase the question, given the function add, that takes a vector and a span (pointer + size)</div><div><br></div><div>ublas::vector<double> add(const ublas::vector<double>& v, const double* p, size_t s)<br></div><div>{</div><div> assert(v.size() == s);</div><div> return v + vector_view<double>(p, s);</div><div>} <br></div></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><br></div><div>Is there something like vector_view already in Ublas that</div><div>1) does not copy the data pointed by p</div></div></div></div></blockquote><div><br></div><div>No. It should be in the proxy (view) class template.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>2) integrates in the ublas expression template machinery as a vector-like expression</div></div></div></div></blockquote><div><br></div><div>See (1)<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><br></div><div>If there is not one already implemented, is it possible to implement one? Is it enough if I model the "Vector Expression" Concept as described in <a href="https://www.boost.org/doc/libs/1_69_0/libs/numeric/ublas/doc/expression_concept.html#2VectorExpression" target="_blank">https://www.boost.org/doc/libs/1_69_0/libs/numeric/ublas/doc/expression_concept.html#2VectorExpression</a> ? Do I also need to inherit from vector_expression?</div></div></div></div></blockquote><div><br></div><div>You could locally extend vector_range by a constructor.</div><div>You could implement a vector_view similar to vector_range. Then yes you need to inherit from vector_expression.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><br></div><div>Thanks! <br></div></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr"><div dir="ltr"><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">From: Cem Bassoy <<a href="mailto:cem.bassoy@gmail.com" target="_blank">cem.bassoy@gmail.com</a>><br>To: ublas mailing list <<a href="mailto:ublas@lists.boost.org" target="_blank">ublas@lists.boost.org</a>><br>Cc: <br>Bcc: <br>Date: Wed, 23 Jan 2019 10:18:22 +0100<br>Subject: Re: [ublas] [Ublas] vector_view over (T*,size)<br><div dir="ltr"><div dir="ltr"><div>Hi there,</div><div><br></div><div>yes, it is possible to do something like this. Please have a look at <a href="https://www.boost.org/doc/libs/1_69_0/libs/numeric/ublas/doc/vector_proxy.html" target="_blank">Vector Proxies.</a></div><div><br></div><div><br></div></div></div><div class="gmail_quote"><div dir="ltr" class="gmail-m_-4817775590245818927gmail-m_4744714021784741303gmail_attr">Am Mo., 21. Jan. 2019 um 11:28 Uhr schrieb dariomt--- via ublas <<a href="mailto:ublas@lists.boost.org" target="_blank">ublas@lists.boost.org</a>>:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hi list,<div><br></div><div>Say I have a (GSL-like) span (which is basically a pointer and a length).</div><div><br></div><div>Is it possible to build a vector-like view over that span, so that the result is usable within the ublas expression template machinery? Some kind of ublas::vector_view(T*, size)?</div><div><br></div><div>The objective is to avoid having to copy all that data into a ublas::vector just to interoperate with other ublas code.</div><div><br></div><div>Thanks in advance!</div></div></blockquote></div>
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