ere are some restrictions on how array expressions may be used that
arise from their types being calculated bottom up and the basic data
type and assignment rules of Stan.</p>
<div id="rectangular-array-expressions-only" class="section level4 unnumbered">
<h4>Rectangular array expressions only</h4>
<p>Although it is tempting to try to define a ragged array expression,
all Stan data types are rectangular (or boxes or other
higher-dimensional generalizations). Thus the following nested array
expression will c