when <code>foo_lupdf</code> is called and
will not drop additive constants when <code>foo_lpdf</code> is called.</p>
<p>If there are <code>_lupdf</code> and <code>_lupmf</code> functions used inside the following
call to <code>foo_lpdf</code>, they will be forced to normalize (return the equivalent
of their <code>_lpdf</code> and <code>_lpmf</code> forms):</p>
<pre class="stan"><code>target += foo_lpdf(z | phi);</code></pre>
<p>If there are no <code>_lupdf</code> or <code>_lupmf</code> functions used in the