b</code>. The interpolation can be extrapolated beyond 0.0 and
1.0, so negative values and values greater than 1.0 are valid (and can
easily be generated by curves such as <code>Curves.elasticInOut</code>). The result
is clamped to the range <a href="dart-ui/FontWeight/w100-constant.html">w100</a>â€“<a href="dart-ui/FontWeight/w900-constant.html">w900</a>.</p>
<p>Values for <code>t</code> are usually obtained from an <code>Animation&lt;double&gt;</code>, such as
an <code>AnimationController</code>.</p>