<div dir="ltr">Dear Matthias,<div><br></div><div>This is what I needed. I did not understand how to use string-ith. �Now I do. �Thank you very much.</div><div><br></div><div>Laurent also sent me links to some beginner's intro videos on You Tube. �</div> <div><br></div><div>I am amazed and eternally grateful that people of your calibre would take the time and trouble to help a tyro like me who must seem like an annoying gnat to you.</div><div><br></div><div>Thank you guys.</div> <div><br></div><div>Saad</div><div>PS I will probably trouble you again. �Will try to keep it to minimum.<br><br><div class="gmail_quote">On Sat, May 12, 2012 at 4:40 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"><div style="word-wrap:break-word"><br><div><div class="im"><div>On May 12, 2012, at 8:35 AM, saad bashir wrote:</div><br> <blockquote type="cite"><div dir="ltr">Dear Matthias,<div><br></div><div>Thank you for replying to me. �I am sure this is laughably basic for you.</div></div></blockquote><div><br></div></div><div>It is basic for me, but there's nothing laughable.�</div> <div class="im"><div><br></div><br><blockquote type="cite"><div dir="ltr"><div>I got what you wrote. �I know string-ith extracts the letter. �My question is how to use it. I have tried various ways of writing both in the def and interaction sections but have not worked out. �Even consulting the Helpdesk has not helped as it does not tell me how to use the fucntion.</div> <div><br></div><div>Sorry if I am being very thick. I really want to do it right.</div><div><br></div></div></blockquote><div><br></div><div><br></div></div><div>If you have a DrRacket in front of you, does it say�</div> <div><br></div><div>� "Welcome to DrRacket, version 5.2.1"</div><div>� Language: Beginning Student.</div><div><br></div><div>in the Interactions WIndow? If not, you need to switch languages with the Language menu.�</div> <div><br></div><div>Once you have switched languages, click run. Then try these interactions:�</div><div><br></div><div>> (string-ith "hello world" 0)</div><div><div>"h"</div><div>> (string-ith "hello world" 1)</div> <div>"e"</div><div>> (string-ith "hello world" 2)</div><div>"l"</div><div>> (string-ith "hello world" 3)</div><div>"l"</div><div>>�</div></div><div><br></div><div> Please let me know which step went wrong previously. -- Matthias</div><div><div class="h5"><div><br></div><div><br></div><div><br></div><div><br></div><br><blockquote type="cite"><div dir="ltr"><div>Saad<br><br><div class="gmail_quote"> On Fri, May 11, 2012 at 11:47 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> The beginning of section 2.1.3 looks like this:<br> <br> <br> > All other operations concerning strings consume or produce data other than strings. Here are some examples:<br> > � � � � string-length consumes a string and produces a (natural) number;<br> ><br> > � � � � string-ith consumes a string s and extracts the one-character substring located at the ith position (counting from 0); and<br> ><br> > � � � � number->string consumes a number and produces a string.<br> ><br> > Also look up substring and find out what it does.<br> <br> Which function do you think extracts a "letter" from a string? [[You can follow the links for the function names. Perhaps it is easier to read the docs.]]<br> <span><font color="#888888"><br> -- Matthias<br> </font></span><div><div><br> <br> <br> <br> On May 11, 2012, at 4:22 PM, saad bashir wrote:<br> <br> > I am back again. �I had a basic inquiry and your help got me started.<br> ><br> > My problem is as follows:<br> ><br> > I have just started to work through 2Htdp (i.e. the second edition) that you had guided me to. Having gone through the prologue I am now on the second chapter, "Fixed-size data." �But have got stuck almost at the start. �I have successfully done the first two exercises but have hit a road block on exercise 3 (section 2.1.3 "Mixing it up"). �I do not know what instruction to use to insert or extract a letter from the ith position. �I think I am doing something wrong when trying to look up things in Helpdesk. Please help.<br> ><br> > Saad<br> ><br> > On Fri, Apr 27, 2012 at 8:32 PM, Danny Yoo <<a href="mailto:dyoo@cs.wpi.edu" target="_blank">dyoo@cs.wpi.edu</a>> wrote:<br> > On Fri, Apr 27, 2012 at 11:27 AM, saad bashir <<a href="mailto:bashir.saad@gmail.com" target="_blank">bashir.saad@gmail.com</a>> wrote:<br> > > Your help was great. �Things are working now. �And a great thank you for<br> > > leading me to the 2d edition of How to Design Programs. �I had not known<br> > > about it.<br> ><br> ><br> > Glad to hear that it's working for you now! �Please feel free to<br> > continue to ask questions on the mailing list; we'll be happy to help.<br> ><br> </div></div><div><div>> ____________________<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></div> </blockquote></div></div></div><br></div></blockquote></div><br></div></div>