<div dir="ltr">Well long day... I was getting lost in basically getting a Number -> Float.<div><br></div><div style>So for example:</div><div style><br></div><div style><div>(: S->F : String -> (Option Float))</div> <div>(define (S->F s)</div><div> (define n (string->number s))</div><div> (and (flonum? n) n))</div><div><br></div><div>(S->F "3") ;; Fails</div><div style><br></div><div style><br></div><div style><div> For some reason I was thinking I had to got through exact? and inexact? type tests and I didn't find the real->double-flonum until just now.</div><div><br></div><div>The below works for me.</div><div><br></div></div> <div style><div><div>(: S->F : String -> (Option Float))</div><div>(define (S->F s)</div><div> (let ((n (string->number s)))</div><div> (if (real? n)</div><div> (real->double-flonum n)</div><div> #f)))</div></div><div><br></div><div style><br></div><div style><br></div><div style><br></div><div style><br></div></div></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Feb 13, 2013 at 10:04 PM, Matthias Felleisen <span dir="ltr"><<a href="mailto:matthias@ccs.neu.edu" target="_blank">matthias@ccs.neu.edu</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br> #lang typed/racket<br> <br> (: S->F : String -> (Option Float))<br> (define (S->F s)<br> (define n (string->number s))<br> (and (flonum? n) n))<br> <br> I assume you mean to convert strings into floats, if possible.<br> <br> But you may like the funny answers better -- Matthias<br> <div class="im HOEnZb"><br> <br> <br> On Feb 13, 2013, at 9:49 PM, Ray Racine wrote:<br> <br> > What is the most efficient way to write the following method in TR?<br> ><br> > (: S->F (String -> (Option Float)))<br> ><br> ><br> </div><div class="HOEnZb"><div class="h5">> ____________________<br> > Racket Users list:<br> > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a><br> <br> </div></div></blockquote></div><br></div>