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Docs: aliasing and component-wise operations.

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Jitse Niesen
2010-11-16 17:28:59 +00:00
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doc/I11_Aliasing.dox
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@@ -128,7 +128,26 @@ functions provided:
\section TopicAliasingCwise Aliasing and component-wise operations
Synopsis: Things like mat = 2 * mat, matA = matA + matB and arr = arr.sin() are safe.
As explained above, it may be dangerous if the same matrix or array occurs on both the left-hand side and the
right-hand side of an assignment operator, and it is then often necessary to evaluate the right-hand side
explicitly. However, applying component-wise operations (such as matrix addition, scalar multiplication and
array multiplication) is safe.
The following example has only component-wise operations. Thus, there is no need for .eval() even though
the same matrix appears on both sides of the assignments.
<table class="example">
<tr><th>Example</th><th>Output</th></tr>
<tr><td>
\include TopicAliasing_cwise.cpp
</td>
<td>
\verbinclude TopicAliasing_cwise.out
</td></tr></table>
In general, an assignment is safe if the (i,j) entry of the expression on the right-hand side depends only on
the (i,j) entry of the matrix or array on the left-hand side and not on any other entries. In that case it is
not necessary to evaluate the right-hand side explicitly.
\section TopicAliasingMatrixMult Aliasing and matrix multiplication