of course variadic templates would be a better solution even if we will restrict the number of users.<br>There are plenty of boost libraries that can help us doing that too, so it should not be too complex.<br><br>What&#39;s about ublas::tie(V1,V2,V3) = M;<br>

That could be useful for applications where Vn are not directly managed by ublas. I mean that you make matrix computations which vectors are then sent to some sort of external outputs. That would be written in one line (like controlling and engine or whatever you can imagine, you know).<br>

that&#39;s splitting up a matrix in vectors .... ?<br><br>Cheers,<br>David<br><br><div class="gmail_quote">On Wed, Jul 14, 2010 at 23:12, Nasos Iliopoulos <span dir="ltr">&lt;<a href="mailto:nasos_i@hotmail.com">nasos_i@hotmail.com</a>&gt;</span> wrote:<br>

<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">



<div>
That would be very useful indeed and not hard to generalize.<br><br>I can see two approaches:<br>1. Exhaustive definition of functions with a varying number of arguments (like 16 (or more) implementations for vector and 16 for matrix), like the one you have in your implementation.<br>

2. Variadic templates (that would be cool, but available only to c++0x compatible compilers) if somebody wants some hints let me know).<br><br>Do you thing this should have any features other than the ones you have in your example? <br>

<br>Best<br>Nasos<br><br><br><br><hr>From: <a href="mailto:jesseperla@gmail.com" target="_blank">jesseperla@gmail.com</a><br>Date: Wed, 14 Jul 2010 10:52:36 -0400<br>To: <a href="mailto:ublas@lists.boost.org" target="_blank">ublas@lists.boost.org</a><br>

Subject: [ublas] A ublas::tie to vector expressions?<div><div></div><div class="h5"><br><br><div>The boost assignment is really nice, but what about the other direction (from vector to scalars)?  This comes up quite often.</div>

<div><br></div><div><div>ublas::vector&lt;double&gt; f()</div><div><div>{</div><div><span style="white-space: pre-wrap;">	</span>ublas::vector&lt;double&gt; v(2);</div>

<div><span style="white-space: pre-wrap;">	</span>v(0) = 1.1;</div><div><span style="white-space: pre-wrap;">	</span>v(1) = 2.1;</div><div><span style="white-space: pre-wrap;">	</span>return v;</div>

<div>}</div></div></div><div><br></div><div><div><span style="white-space: pre-wrap;">	</span>double x;</div><div><span style="white-space: pre-wrap;">	</span>double y;</div><div><span style="white-space: pre-wrap;"><br>

<br><br></span></div><div><span style="white-space: pre-wrap;">	</span>ublas::vector&lt;double&gt; v(2);</div><div><span style="white-space: pre-wrap;">	</span>v(0) = 1.1;</div><div><span style="white-space: pre-wrap;">	</span>v(1) = 2.1;</div>



<div><br></div><div><span style="white-space: pre-wrap;">	</span>ublas::tie(x, y) = v;</div></div><div><span style="white-space: pre-wrap;">	</span>ublas::tie(x, y) = f(); //With function</div>

<div><br></div><div><div><span style="white-space: pre-wrap;">	</span>ublas::matrix&lt;double&gt; mat(2,2); //....</div><div><span style="white-space: pre-wrap;">	</span>ublas::tie(x, y) = row(mat, 0);</div>

</div><div><br></div><div><div><span style="white-space: pre-wrap;">	</span>ublas::vector&lt;int&gt; v2(2);</div><div><span style="white-space: pre-wrap;">	</span>v2(0) = 1;</div><div>

<span style="white-space: pre-wrap;">	</span>v2(1) = 2;</div></div><div><br></div><div>        int z;</div><div>        ublas::tie(x, z); //With different types</div><div><br></div><div><br></div><div>
<div>
<br></div></div><div>For vector expressions, this seems to be easy enough to do.  See the attached basic implementation for 2 parameters.  With a little boost preprocessor, this could be fairly general.  What do people think?  Are there any boost PP who could generalize this?</div>



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