Triangle}(y|-1,1)\)</span>. This value is coded in Stan as
<code>log1m(fabs(y))</code>. The function <code>log1m</code> is defined so
that <code>log1m(x)</code> has the same value as <code>log(1.0-x)</code>, but the
computation is faster, more accurate, and more stable.</p>
<p>The constrained type <code>real&lt;lower=-1,upper=1&gt;</code> declared for <code>y</code> is
critical for correct sampling behavior. If the constraint on <code>y</code>
is removed from the program, say by declaring <code>y</code> as 