Straightforward to use a struct, or a a tagged value like (cons 'cm 10) and then have your procedure parse the argument. Deren <div class="gmail_quote">On Sep 30, 2014 11:14 AM, "Tomi Pieviläinen" <<a href="mailto:tomi.pievilainen%2Bracket@iki.fi">tomi.pievilainen+racket@iki.fi</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">First apologies to Alexsandro Soares, if I'm intruding, but I wasn't sure if you were on the mailing list and you were asking about this in June. I tested how well Racket runs on the Lego Mindstorms EV3 (with ev3dev), and found out that there is enough memory on the device to get a REPL running. The loading time is somewhat annoying, but not prohibitive. I also started creating a library for using the ev3dev kernel exposed file based API. I tested that I can use the color and ultrasonic sensors, and motors. The rest is simple from those. I'm a bit stuck by trying to grok Racket better. I'm thinking about possibility to have some kind of "typed literals" for distance, time and angle, so that I could use (move-robot 11cm) or (move-robot 11s) like calls, instead of having separate functions for time and distance variables, or having to create the values with (cm 11) or such. Not sure if that makes any sense, but I was thinking that it might feel more natural and also I'm interested in seeing how easily it could be done. -- Tomi Pieviläinen, <a href="tel:%2B358%20400%20487%20504" value="+358400487504">+358 400 487 504</a> A: Because it disrupts the natural way of thinking. Q: Why is top posting frowned upon? ____________________ Racket Users list: <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </blockquote></div>