[issue23660] Turtle left/right inverted when using different coordinates orientation

[Carol Willing]

Carol Willing  added the comment:

Reopened at the request of the original submitter.

--
resolution: remind -> 
stage: resolved -> patch review
status: closed -> open

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[issue23660] Turtle left/right inverted when using different coordinates orientation

[Andre Roberge]

Andre Roberge  added the comment:

I am sorry to hear that this bug was closed based on the unproven assumption 
that this would impact teaching material.  I have *never* seen any pedaggical 
material for the turtle module where the instructor wrote "use left() to have 
the turtle turn right, and vice-versa".

I file the original bug report and the code to fix it based on a report on the 
edu-sig mailing list, more than 3 years ago 
https://mail.python.org/pipermail/edu-sig/2015-March/011207.html

This bug makes it pedagogically unwise to set the coordinate system as 
described since a left() instruction makes the turtle turns right, and 
vice-versa. So, no one using the turtle module to teach can currently use this 
type of coordinate choice as it would be too confusing to students.  The 
solution provided would have fixed that.

If that is the final decision, then so be it - and I will advise people to use 
Brython's turtle module instead as it does not have this bug.

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[issue23660] Turtle left/right inverted when using different coordinates orientation

[Carol Willing]

Carol Willing  added the comment:

Hi aroberge,

Thanks for filing this issue.

I'm triaging all of the open 'turtle' issues. I'm closing this issue since 
introducing this suggested change would impact teaching materials and resources 
that have already been published. This would be a change that would break 
compatibility.

I've marked the resolution as "Remind" if someone in the future wishes to open 
a documentation issue.

--
nosy: +willingc
resolution:  -> remind
stage:  -> resolved
status: open -> closed

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[issue23660] Turtle left/right inverted when using different coordinates orientation

[Andre Roberge]

New submission from Andre Roberge:

The turtle module using screen coordinates such that the vertical coordinate 
increases vertically on the screen. This orientation is different from the 
traditional orientation for graphics programs.

It is possible to set coordinates with the normal orientation using the 
setworldcoordinates function, e.g.

 from turtle import *
 setworldcoordinates(0, 400, 400, 0)

With the above choice, the y coordinate increases as the turtle moves down on 
the screen.  However, doing so inverts the role of left() and right().

I have attached a diff file which introduces a change needed so that left() 
and right() behave correctly with this different orientation.

--
files: turtle_diff.txt
messages: 238037
nosy: aroberge
priority: normal
severity: normal
status: open
title: Turtle left/right inverted when using different coordinates orientation
type: behavior
versions: Python 3.4
Added file: http://bugs.python.org/file38473/turtle_diff.txt

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