[ruby-talk:15286] Re: Turtle graphics anyone?

Hi

I have a chance at a Career Awareness Day this friday to introduce your
program and Ruby to teachers and students at the local middle school. I hope
it will be fun and an eye opener for all of us. As a newcomer to Ruby I am
continually amazed at how much work can be done in just a few lines of code.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Craig Luthy, CAE Services, Deere & Company, Moline, IL  61265
[e-mail]


> -----Original Message-----
> From:	Mathieu Bouchard [SMTP:[e-mail]]
> Sent:	Tuesday, May 15, 2001 5:17 PM
> To:	[e-mail]; meredith
> Cc:	ruby-talk ML; [e-mail]
> Subject:	[ruby-talk:15217] Re: Turtle graphics anyone?
> 
> On Wed, 16 May 2001, meredith wrote:
> > I've been trying to persuade my teacher friends to use Ruby to teach 
> > their kids. The bottom line for most of them is that they need to have 
> > turtle graphics. If I knew TK I might attempt it myself, but I don't and
> 
> > so the learning curve would be way too big. Anyone out there want to 
> > take it on?
> > Getting it into the schools is a really good way to help a language 
> > catch on.
> 
> 
> 
> Three parts:
> 
> 	* a sample program using the turtle
> 
> 	* the turtle package (yellow window)
> 		commands typed in the red box may be
> 		"forward", "back", "right", "left", or any
> 		ruby expression.
> 
> 	* the listener package (type commands in the red box)
> 		I originally wrote this last part for another project;
> 		it has a command history.
> 
> ----------------8<----------------cut-here----------------8<--------------
> --
> 
> # this draws a recursive tree.
> 
> # unfortunately you'll have to put the whole def on one line to feed it to
> # the listener, unless you wrap it in $listener.instance_eval { } just
> # before the mainloop.
> 
> def tree(d,n)
> 	return if n<1
> 	forward d
> 	left 45
> 	tree d*3/4,n-1
> 	right 90
> 	tree d*3/4,n-1
> 	left 45
> 	back d
> end
> 
> back 50
> tree 50,6
> 
> --------8<----------------cut-here----------------8<-------- TkTurtle.rb
> 
> #       Ruby/Tk Turtle Graphics
> #       Copyright (c) 2001 by Mathieu Bouchard
> #       under the same license as Ruby itself
> 
> require 'tk'
> require 'TkRubyListener'
> 
> $root = TkRoot.new {
> 	title "Tortue"
> }
> $canvas = TkCanvas.new($root) {
> 	background "#888800" # dark yellow
> 	width 512
> 	height 384
> }.pack
> $listener = TkRubyListener.new($root,60,8)
> $listener.frame.pack("fill"=>"both")
> 
> module Turtle
> 	def turtle_init
> 		@pos_x = $canvas.width/2
> 		@pos_y = $canvas.height/2
> 		@angle = 0
> 		@turtle_lines ||= (0...3).map {|i|
> 			l = TkcLine.new($canvas,0,0,0,0)
> 			l.fill "white"
> 			l
> 		}
> 		turtle_draw
> 	end
> 	def forward(distance)
> 		nx = @pos_x + distance * Math.sin(@angle)
> 		ny = @pos_y - distance * Math.cos(@angle)
> 		TkcLine.new($canvas,@pos_x,@pos_y,nx,ny).fill "black"
> 		@pos_x = nx
> 		@pos_y = ny
> 		turtle_draw
> 		return distance
> 	end
> 	def right(angle)
> 		@angle += angle * Math::PI / 180
> 		turtle_draw
> 		return angle
> 	end
> 	def back(distance); forward -distance; end
> 	def left(angle); right(-angle); angle; end
> 
> 	def turtle_draw
> 		@turtle_points = 
> 		[[8,0],[-8,0],[0,20]].map {|x,y| [
> 			@pos_x + y * Math.sin(@angle) + x *
> Math.cos(@angle),
> 			@pos_y - y * Math.cos(@angle) + x * Math.sin(@angle)
> 		]}
> 		(0...3).each {|i| @turtle_lines[i].coords(*(
> 			@turtle_points[i] + @turtle_points[(i+1)%3] ))
> 		}
> 	end
> end
> 
> $listener.extend Turtle
> $listener.turtle_init
> # $listener.instance_eval { }
> Tk.mainloop
> 
> ----8<----------------cut-here----------------8<---- TkRubyListener.rb
> #       Interactive Ruby/Tk
> #       Copyright (c) 2000,2001 by Mathieu Bouchard
> #       under the same license as Ruby itself
> 
> require "tk"
> 
> class TkRubyListener
> 	attr_reader :entry
> 	attr_reader :text
> 	attr_reader :hist
> 	attr_reader :frame
> 
> 	def initialize(parent,w=80,h=10)
> 		@frame = TkFrame.new(parent)
> 
> 		@hist = []
> 		@histn = 0
> 		_line = @line = TkVariable.new
> 
> 		@text = TkText.new(frame) {
> 			background "#006090"
> 			foreground "#ffffff"
> 			highlightbackground "#000000"
> 			highlightcolor "#ffffff"
> 			width w
> 			height h
> 		}.pack("fill"=>"both")
> 
> 		@entry = TkEntry.new(frame) {
> 			background "#900060"
> 			foreground "#ffffff"
> 			highlightbackground "#000000"
> 			highlightcolor "#ffffff"
> 			width w
> 			textvariable _line
> 		}.pack("fill"=>"x")
> 
> 		@entry.bind("Return") { self.eval_entry   }
> 		@entry.bind("Up")     { self.history_up   }
> 		@entry.bind("Down")   { self.history_down }
> 	end
> 
> 	def line=(value)
> 		# bug?
> 		# @line.value = value
> 
> 		@entry.delete("0","end")
> 		@entry.insert("0",value)
> 	end
> 	def line()
> 		@line.value
> 	end
> 
> 	def hist_peek(i)
> 		hist[i]
> 	end
> 
> 	def histn=(v)
> 		@histn = v > hist.length ? hist.length : v < 0 ? 0 : v
> 	end
> 	attr_reader :histn
> 
> 	def add_history(v)
> 		@hist.push v
> 		self.histn = hist.length
> 	end
> 
> 	# there is a bug that causes spurious '(undef)' to appear (and
> possibly
> 	# not even executing the code) but i don't know what it is
> 	# this was in perl, may not occur in ruby.
> 	def eval_entry
> 		@text.delete("1.0", "end")
> 		@text.insert("end","\n<< #{self.line}\n")
> 		_result_,_err_ = nil
> 		begin
> 			_result_ = eval line
> 		rescue Exception => _err_
> 			text.insert("end","!> #{_err_}\n")
> 		end
> 		if not _err_
> 			@text.insert("end",">> #{_result_.inspect}\n")
> 		end
> 
> 		add_history(line)
> 		self.line = ""
> 		text.yview("moveto",1)
> 	end
> 
> 	def history_up
> 		self.histn -= 1
> 		self.line = hist_peek(histn)
> 		entry.cursor = 'end'
> 	end
> 
> 	def history_down
> 		self.histn += 1
> 		self.line = hist_peek(histn)
> 		entry.cursor = 'end'
> 	end
> end
> 
> ----------------8<----------------cut-here----------------8<--------------
> --
> 
> matju
> 
>