<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Dear Stephen,</div><div><br></div><div>Can you let me know firstly which function is responsible for printing the output?</div><div><br></div><div>Secondly, can you add comments explaining how it works? I can generally appreciate what you are doing, but I'm not a Scheme programmer so I might not understand the exact detail correctly.</div><div><br></div><div>Thanks</div><div>Samuel</div><br><div><div>On 4/05/2010, at 1:01 AM, Stephen Bloch wrote:</div><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><font class="Apple-style-span" color="#000000"><br></font></div>Well, that particular algorithm relies very heavily on mutation, but here's a functional version.</div><div><br></div><div><div>(define (door-open door)</div><div> (doh door 99))</div><div><br></div><div>(define (doh door pass)</div><div> (cond [(zero? pass) true]</div><div> [(= (remainder door (+ pass 1)) pass)</div><div> (not (doh door (- pass 1)))]</div><div> [else</div><div> (doh door (- pass 1))]))</div><div><br></div><div>(define doors (build-list 100 door-open))</div><div><br></div><div><br></div><div><br></div><div>Somewhat shorter but more cryptic:</div><div><div><br></div><div>(define (door-open door)</div><div> (doh door 99))</div><div><br></div><div>(define (doh door pass)</div><div> (or (zero? pass)</div><div> (not (boolean=? (= (remainder door (+ pass 1)) pass)</div><div> (doh door (- pass 1))))))</div><div><br></div><div>(define doors (build-list 100 door-open))</div><div><br></div><div><br></div><div><br></div><div>Even shorter, but takes some math (and illustrates how artificial this problem is :-) :</div><div><br></div><div>(define (door-open door)</div><div> (integer? (sqrt (+ door 1))))</div><div><br></div><div>(define doors (build-list 100 door-open))</div><div><br></div></div></div><br><br><div>
<span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div>Stephen Bloch</div><div><a href="mailto:sbloch@adelphi.edu">sbloch@adelphi.edu</a></div><div><br></div></span><br class="Apple-interchange-newline">
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