<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">I have a 64-bit integer obtained by the FLI from external storage. It was obtained by reading two 32-bit unsigned values and depositing them into a zero valued integer. Now I want to sign-extend the result so that if it has its MSB set, the value will be a twos-complement negative value.<div><br></div><div><div>(defun read-int64 (ptr)</div><div> (let ((v (read-uint64 ptr)))</div><div> (if (logbitp 63 v)</div><div> (- v #.(ash 1 64))</div><div> v)))</div><div><br></div><div>But this looks inelegant to me, requiring the storage of a constant #.(ash 1 64) used in a subtraction operation.</div><div><br></div><div>Been racking my brain on the BOOLE operations and the LOGNOT et al, looking for a more elegant solution to this. Not a high-value item, just curious.</div><div><br></div><div>
<span class="Apple-style-span" style="font-family: Helvetica; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><span class="Apple-style-span" style="font-size: 12px; ">Dr. David McClain</span></div><div><span class="Apple-style-span" style="font-size: 12px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Chief Technical Officer</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Refined Audiometrics Laboratory</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">4391 N. Camino Ferreo</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Tucson, AZ 85750</div><div style="min-height: 14px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">email: <a href="mailto:dbm@refined-audiometrics.com" target="_blank">dbm@refined-audiometrics.com</a></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">phone: 1.520.390.3995</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">web: <a href="http://www.refined-audiometrics.com/" target="_blank">http://www.refined-audiometrics.com</a></div><div><br></div></span></div></div></div></span><br class="Apple-interchange-newline">
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