<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Feb 14, 2012, at 12:51 AM, Erik Silkensen wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Instead of calling fib-less-than-n recursively, you could add a loop inside, for example something like,<div><br></div><div><div><div><div>(define (fib-less-than-n n)</div><div> (define fib (mk-fib))</div><div> (let loop ([vs '()])</div><div> (let ([fib-val (fib)])</div><div> (if (>= fib-val n)</div><div> (reverse vs)</div><div> (loop (cons fib-val vs))))))</div></div></div></div></div></blockquote><div><br></div></div><div>Let's generalize and abstract this to "take-while":</div><div><br></div><div>(define (take-while generator test?)</div><div> (reverse</div><div> (let loop [[vs '()]]</div><div> (let [[value (generator)]]</div><div> (if (test? value)</div><div> (loop (cons value vs))</div><div> vs)))))</div><div><br></div><div>(define (fib-less-than-n n)</div><div> (take-while (mk-fib) (lambda (value) (< value n))))</div><div><br></div><div>[I haven't typed this code in and tested it, so there may be typos.]</div><div><br></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; 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; font-size: medium; "><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">
</div>
<br></body></html>