wo dimensional array <code>real[ , ]</code>, <code>y</code> will
be a one-dimensional array of real values (type <code>real[]</code>). If ’ys<code>is a matrix, then</code>y<code>will be a real value (type</code>real`). To loop over
all values of a two-dimensional array using foreach statements would
require a doubly-nested loop,</p>
<pre><code>real yss[2, 3];
for (ys in yss)
  for (y in ys)
    ... do something with y ...</code></pre>
<p>whereas a matrix can be looped over in one foreach statement</p>
<pr