<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">HI,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">There seems to be a lot of misunderstanding about this issue. Hopefully, the following can help clear it up.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">0. The turtle module includes functions named left() and right() which result in the turtle rotating in the corresponding direction on the screen.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">1. The turtle implementation includes a function, setworldcoordinates(), which allows one to have user-defined coordinates (both for the width and height of the world) including a choice as to which in which direction the coordinates are increasing. The issue has nothing to do with what choice is "best"; any user is free to use whatever they want.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">2. In the current implementation, if one choses some particular orientation for the coordinates, the role of left() and right() are inverted and no longer correspond to what the user sees on the screen.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">The submitted fix simply ensures that, no matter what one chooses for the world coordinates via setworldcoordinates, when right() is called in a program, the turtle turns right and not left.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">André</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><br><div class="gmail_quote"><div dir="ltr">On Tue, Jun 19, 2018 at 2:29 PM Yoshiki Ohshima <<a href="mailto:Yoshiki.Ohshima@acm.org" target="_blank">Yoshiki.Ohshima@acm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">I also stick my nose here.<div><br></div><div>The notion of "in computer graphics Y goes down" is not as true as some people think. The graphics you are looking at right now on your computer most likely to have gone through some programs that use "Y goes up" scheme (such as GLSL).</div><div><br></div><div>Only if you are talking about pixels and raster graphics, you could say that there is a dominant convention to make Y go down, but in with vectors, there is no such dominance.</div><div><br></div><div>For end-users, why does it matter how actually pixels are stored in the actual memory? Computer is medium that can simulate anything; so the decision should not be based on what computer does at the lower levels.</div><div><br></div><div>Once we leave from what computer does at low-level, there are math text books, which are dominantly "Y-up". Why do they have to know two different conventions? Unless, of course, learning the fact that the coordinate system is just a convention and can be different.</div><div><br></div><div>Also there may be a case where the particular turtle graphics implementation is tied to the lower level pixel representation. But is basically mixing different abstraction levels, and unless you want to teach about mixing abstraction levels, it is a bad starting point.</div><div><br></div><div>In summary: the statement <span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:small;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">"in computer graphics Y goes down" is a wrong argument for turtle graphics to use Y-down coordinate system. Then, for turtles and for end-users, there is an existing convention to make Y go down. So that should be a better default.</span></div><div><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jun 18, 2018 at 9:54 AM, Kevin Cole <span dir="ltr"><<a href="mailto:kevin.cole@novawebdevelopment.org" target="_blank">kevin.cole@novawebdevelopment.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div style="font-family:verdana,sans-serif;color:#4c1130">Sticking my nose in where it don't belong. ;-) But that's never stopped me before. ;-)</div><div style="font-family:verdana,sans-serif;color:#4c1130"><br></div><div style="font-family:verdana,sans-serif;color:#4c1130">First "I are not a teacher". At least, not in any formal sense of the word. Second, some would say "I are not a programmer". I don't listen to those people.</div><div style="font-family:verdana,sans-serif;color:#4c1130"><br></div><div style="font-family:verdana,sans-serif;color:#4c1130">In spite of the common "in computer graphics Y goes down", does that make sense to new learners? I've gotten used to various coordinate systems, but the first time I had to work with graph paper and plotting (and, for that matter, maps) one goes "up" ("north", "forward") for Y. Then again, maybe the average learner isn't quite as flexible these days, and telling them after they've gotten used to a system that they have to flip everything upside down and backwards isn't a great idea. I attribute my own flexibility not to any innate ability but rather to learning during a time when architectures OS's and languages were changing fast enough that there wasn't time to become set in one's ways.<br></div><div class="gmail_extra"><br></div><div class="gmail_extra"><div>[Note: Grammatical "mistakes" above are meant as weak -- very weak -- humor. At least, most are.]</div><span class="m_-4277952432231115172m_-6144111028876116668HOEnZb"><font color="#888888">-- <br><div class="m_-4277952432231115172m_-6144111028876116668m_-1241903755420016171gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>
<div dir="ltr">
<div>
<div>
<div><b><span style="color:#0b5394"><span style="font-size:large">Kevin Cole</span></span></b><br><a title="NOVA Web Development Co-Op" href="http://novawebdevelopment.org" target="_blank"><img src="https://docs.google.com/uc?export=download&id=0BwTZk3m0X_cjWkluSUtxQjJQTXc&revid=0BwTZk3m0X_cjbG5PLzAyZE8wY1lUYldSMzVQdkNkd3lQRDNRPQ" width="96" height="33"></a></div>
NOVA Web Development Co-Op</div>
<div><a href="http://novawebdevelopment.org/" target="_blank">http://novawebdevelopment.org/</a></div>
<span style="color:#888888">Arlington, VA</span></div></div></div></div></div></div></div>
</font></span></div></div>
<br>_______________________________________________<br>
Edu-sig mailing list<br>
<a href="mailto:Edu-sig@python.org" target="_blank">Edu-sig@python.org</a><br>
<a href="https://mail.python.org/mailman/listinfo/edu-sig" rel="noreferrer" target="_blank">https://mail.python.org/mailman/listinfo/edu-sig</a><br>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="m_-4277952432231115172m_-6144111028876116668gmail_signature" data-smartmail="gmail_signature">-- Yoshiki<div><br></div></div>
</div>
_______________________________________________<br>
Edu-sig mailing list<br>
<a href="mailto:Edu-sig@python.org" target="_blank">Edu-sig@python.org</a><br>
<a href="https://mail.python.org/mailman/listinfo/edu-sig" rel="noreferrer" target="_blank">https://mail.python.org/mailman/listinfo/edu-sig</a><br>
</blockquote></div></div>