-coroutine as argument, so that using the coroutine
        passed as argument to <span class="emphasis"><em>coroutine-function</em></span> is the only
        way to transfer data and execution control back to the caller. Both coroutine
        types take the same template argument. For <span class="emphasis"><em>asymmetric_coroutine&lt;&gt;::pull_type</em></span>
        the <span class="emphasis"><em>coroutine-function</em></span> is entered at <span class="emphasis"><em>asymmetric_coroutine&lt;&gt;::pul