"instead of crashing when a non-number string is given, return a special value that says there is something wrong" ?<br>That may be an introduction to error-handling, which is a big part of programming?<br><br><div class="gmail_quote"> On Thu, Nov 12, 2009 at 12:42, wooks <span dir="ltr"><<a href="mailto:wookiz@hotmail.com">wookiz@hotmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div class="im"><br> <br> On Nov 12, 11:32 am, "Geoffrey S. Knauth" <<a href="mailto:ge...@knauth.org">ge...@knauth.org</a>> wrote:<br> > On Nov 12, 2009, at 05:44, wooks wrote:<br> ><br> > > On Nov 9, 2:50 pm, Matthias Felleisen <<a href="mailto:matth...@ccs.neu.edu">matth...@ccs.neu.edu</a>> wrote:<br> > >> 1. Use HtDP/2e to get started. Then switch.<br> > > So I'm looking at it and wondering how to explain why (string->number<br> > > "hello world") returns a boolean.<br> ><br> > My documentation for beginner language says:<br> ><br> > string->number : (string -> (union number false))<br> ><br> > Purpose: to convert a string into a number, produce false if >impossible<br> ><br> <br> </div>Yes I saw that. I was hoping be able to give a different answer than<br> "thats the way it was defined".<br> <div><div></div><div class="h5">_________________________________________________<br> For list-related administrative tasks:<br> <a href="http://list.cs.brown.edu/mailman/listinfo/plt-scheme" target="_blank">http://list.cs.brown.edu/mailman/listinfo/plt-scheme</a><br> </div></div></blockquote></div><br>