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<p>&nbsp;<p>
<hr noshade size="5">
<h2><a name="MatElt"></a>
MatElt
</h2>

Returns or modifies an matrix entry or row.

<p><p>

<h3>
Syntax:
</h3>
<pre>a := MatElt(M, row, col);
a := M[row][col];
M[row][col] := a;
r := M[row];
M[row] := L;</pre>

<p>

<table>
<tr>
<td>element of the ring the matrix entries come from</td>
<td><pre>  a  </pre></td>
<td></td>
</tr>
<tr>
<td>matrix</td>
<td><pre>  M  </pre></td>
<td></td>
</tr>
<tr>
<td>small integer</td>
<td><pre>  row  </pre></td>
<td></td>
</tr>
<tr>
<td>small integer</td>
<td><pre>  col  </pre></td>
<td></td>
</tr>
<tr>
<td>an object of the type "KANT matrow"</td>
<td><pre>  r  </pre></td>
<td></td>
</tr>
<tr>
<td>either a list, a "KANT matrix", or a "KANT matrow"</td>
<td><pre>  L  </pre></td>
<td></td>
</tr>
</table>

<p>


<h3>
Description:
</h3>
The first two syntax variants are equivalent and return the
(<tt> row</tt>, <tt> col</tt>)-th entry of the matrix <tt> M</tt>.\smallskip

The third variant sets a single entry of the matrix. The
object must be convertible to an element of the ring over which
the matrix is defined.

The fourth syntax retrieves a matrix row. This is an object of
the type "KANT matrow". This object can be converted to a proper
matrix (with only one row) with a call of <tt> IsMat</tt>. It can also
be used as a row for another matrix.

The fifth syntax sets a row of the matrix. For this purpose the
matrix is converted into a list of rows (of the type "KANT matrix").
Then the <tt> row</tt>-th entry of this list is either replaced by
of set to the right hand side of the assignment. Now <tt> M</tt> is still
a list a should be converted to a matrix with a call of <tt> IsMat</tt>.
<tt> IsMat</tt> also determines a ring all entries of the matrix belong to.
So by setting a new row or modifying an existing one the matrix might
change its ring.

<p><p>

<p>
<hr>
<p>
<h3>
Example:
</h3>
Get certain entries of the matrix
 \left(\begin{array}{cccc} 3 & 7 & 10 & 2 90 & 101 & 87 & 2
12 & 34 & 2 & 0 20 & 25 & 40 & 1 \end{array}right)
and modify them. 
<pre>

kash> M := Mat(Z,[[3,7,10,2],[90,101,87,2],[12,34,2,0],[20,25,40,1]]);
[  3   7  10   2]
[ 90 101  87   2]
[ 12  34   2   0]
[ 20  25  40   1]
kash> MatElt(M,1,1);
3
kash> M[2][2];
101
kash> r:=M[4];
[20 25 40  1]
kash> TYPE(r);
"KANT matrow"
kash> IsMat(r);
true
kash> r;
[20 25 40  1]
kash> TYPE(r);
"KANT matrix"
kash> M[4][4]:=22;;M;
[  3   7  10   2]
[ 90 101  87   2]
[ 12  34   2   0]
[ 20  25  40  22]
kash> M[3]:=[-1,2,-1,4];;M;
[ [ 3  7 10  2], [ 90 101  87   2], [ -1, 2, -1, 4 ], [20 25 40 22] ]
kash> IsMat(M);
true
kash> M;
> [  3   7  10   2]
[ 90 101  87   2]
[ -1   2  -1   4]
[ 20  25  40  22]

</pre>

<p>


<hr>

<p>
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