de> is crucial to defining streams with feedback loops.</li>
<li>However, there are cases where we need further, explicit uses of <code>delay</code>.</li>
<li>For example, solving the differential equation <span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi>d</mi><mi>y</mi><mi mathvariant="normal">/</mi><mi>d</mi><mi>t</mi><mo>=</mo><mi>f</mi><mo stretchy="false">(</mo><mi>y</mi><mo stretchy="false">)</mo></mrow><annotation encoding="application/x-tex">dy/dt = f(y)</annotation></semant