<font color='black' size='2' face='arial'><span class="Apple-style-span" style="font-size: small;">Hello schemers</span>
<div><span class="Apple-style-span" style="font-size: small;"><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small;">what if I have program of massage passing and I have to return the object when it is defined.</span></div>

<div><span class="Apple-style-span" style="font-size: small;">example-</span></div>

<div><span class="Apple-style-span" style="font-size: small;"><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">(define (single-order)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">(let (</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">        </font></span><font class="Apple-style-span" color="#2F4F4F">(delivery&nbsp;#f)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">        </font></span><font class="Apple-style-span" color="#2F4F4F">)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">(define (the-order req)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">(cond ((eq? req 'available) &nbsp;available)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F">(</font></span><span class="Apple-style-span" style="white-space: pre-wrap; "><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">else</font></span></font></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F"> (</font></span><span class="Apple-style-span" style="white-space: pre-wrap; "><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">error</font></span></font></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F"> "</font></span><span class="Apple-style-span" style="white-space: pre-wrap; "><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">the-order</font></span></font></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F">: unknown </font></span><span class="Apple-style-span" style="white-space: pre-wrap; "><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">req</font></span></font></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F">: " </font></span><span class="Apple-style-span" style="white-space: pre-wrap; "><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><span class="Apple-style-span" style="font-size: small;"><font class="Apple-style-span" color="#2F4F4F">req</font></span></font></span><span class="Apple-style-span" style="font-family: monospace; white-space: pre-wrap; font-size: medium; "><font class="Apple-style-span" color="#2F4F4F">))</font></span></div>

<div><font class="Apple-style-span" color="#2F4F4F"><span class="Apple-style-span" style="white-space: pre-wrap; font-size: medium; "></span></font><span class="Apple-style-span" style="font-size: small; "><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"><font class="Apple-style-span" color="#2F4F4F">    )</font></font></span></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F"><font class="Apple-style-span" face="Arial, Helvetica, sans-serif"></font></font></span><font class="Apple-style-span" color="#2F4F4F">)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F"><br>
</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F">(define (available)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">(set! delivery #t))</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F"><br>
</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F">the-order</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F">&nbsp;&nbsp; )</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F"><br>
</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F">(define (available object)</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" color="#2F4F4F">    </font></span><font class="Apple-style-span" color="#2F4F4F">((object 'available)))</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small; "><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small; ">=&gt; now when I will run it like</span></div>

<div><span class="Apple-style-span" style="font-size: small; "><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small; "><font class="Apple-style-span" color="#2F4F4F">(define mcdon(single-order))</font></span></div>

<div><span class="Apple-style-span" style="font-size: small; "><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small; ">- it should return mcdon instead of &lt;#unspecified&gt;</span></div>

<div><span class="Apple-style-span" style="font-size: small; "><br>
</span></div>

<div><span class="Apple-style-span" style="font-size: small; ">Any ideas??&nbsp;</span></div>

<div><span class="Apple-style-span" style="font-size: small;"><span class="Apple-tab-span" style="white-space:pre">    </span><br>
</span><br>

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