[racket] New turtle graphics package + a few questions

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Sat Feb 23 13:19:05 EST 2013

Nice! Keep pushing this project -- Matthias

On Feb 22, 2013, at 3:30 PM, Daniel Prager wrote:

> Thanks Sam and Matthias for the tips:  I've been able to clean up the directory structure and
> add a (save-movie) command that writes out an animated gif.  
> Example: https://github.com/danprager/turtlegraphics/blob/master/docs/animated-circle.gif
> Matthias wrote:
> > Thanks, that's great. In what way did you find the existing one lacking?
> I did start with that existing package, but initially wanted to simplify the process of drawing pictures interactively, and boost the immediate appeal for my kids.  Specifically, I wanted:
> * input and output directly in Dr Racket's REPL window, rather than an an "edit definitions-run-close graphics window" cycle.
> * a realistic image of a turtle, rather than a triangle.
> Based on observation of my kids I made improvements to enhance usability and appeal.  Main additions:
> * (undo) and (redo) to improve interactivity
> * facility to change the turtle's image into e.g. a pink girl
> * replay all the turtle's steps as an animation: (movie) 
> * (show-program)  to recap the interactive commands used so far for copying into the definitions window
> Of these (movie) is definitely the "wow" feature.  
> BTW: If someone would like to contribute, a bit-blt-based "color-in" operation, that would be great.
> I should add that after taking Shriram's recent online PLAI course I restructured the whole thing around a sugared and desugared language.  This approach allowed me -- amongst other simplifications -- to cleanly separate out the chopping-out-into-frames needed for animation from the rest of the code.  Previously both modes of movement were smooshed together.
> Dan
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