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</h2>
<ul>
<li>In this section, we will modify the interpreter to support lazy evaluation.</li>
<li>The lazy evaluator <em>delays</em> certain arguments, transforming them into <em>thunks</em>.</li>
<li>The expression in a thunk does not get evaluated until the thunk is <em>forced</em>.</li>
<li>A thunk gets forced when its value is needed:
<ul>
<li>when passed to a primitive procedure;</li>
<li>when it is the predicate of conditional