I am trying to open the app, but it keeps loading without opening.
What can I do?

Thank you very much!

I hope this code here will be a bit easier on the eye. :) I also added some comments to make it more readable.

/* Penrose tilings of the P2 type. There are two functions in this program that call themselves and each other recursively: halfKite and halfDart. Note that each function draws an equilateral triangle from the top, and that both functions always exit with the turtle having the same heading as when they entered. */ val Phi = (1 + math.sqrt(5)) / 2 // The golden ratio var kiteColor = green var dartColor = blue def halfKite(depth: Int, length: Double, mirrored: Int): Unit = { if(depth == 0) { // Base case: setFillColor(kiteColor) right(mirrored * 162) forward(length) right(mirrored * 108) forward(length / Phi) right(mirrored * 108) hop(length) left(mirrored * 18) } else { // Recursive case: we draw a half kite by means of // drawing two smaller half kites and a half dart. // // Move the turtle to the right position for the // half dart... right(mirrored * 162) hop(length / (Phi + 1)) left(mirrored * 54) // And draw it! halfDart(depth - 1, length / (Phi + 1), mirrored) right(mirrored * 54) hop(length / Phi) left(mirrored * 54) halfKite(depth - 1, length / Phi, mirrored) right(mirrored * 36) // Note that this half kite is mirrored with // respect to the larger one it is a part of. halfKite(depth - 1, length / Phi, -mirrored) left(mirrored * 162) hop(length) right(mirrored * 18) } } def halfDart(depth: Int, length: Double, mirrored: Int): Unit = { // As in the case of the half kite, we again // distinguish between a base case and a recursive // case. The recursive half dart is composed of one // half kite (mirrored) and a half dart (not mirrored). if(depth == 0) { setFillColor(dartColor) right(mirrored * 126) forward(length) right(mirrored * 144) forward(length * Phi) right(mirrored * 144) hop(length) left(mirrored * 54) } else { left(mirrored * 126) hop(length) right(mirrored * 18) halfKite(depth - 1, length, -mirrored) left(mirrored * 162) hop(length) right(mirrored * 126) halfDart(depth - 1, length / Phi, mirrored) right(mirrored * 126) hop(length / Phi) right(mirrored * 18) } } // The sun pattern can be drawn by drawing 10 half kites, // half of which are mirrored. def sun(depth: Int, length: Double): Unit = { repeat(5) { halfKite(depth, length, -1) right(36) halfKite(depth, length, 1) right(36) } } // Some scripting to call the sun function six times, // with a depth ranging from 1 to 6. // // After each call, a spin is given to the color of // both kite and dart. toggleFullScreenCanvas() repeatFor(1 to 6) { i => cleari() setBackground(black) setPenColor(black) setPenThickness(6 - i) setSpeed(superFast) right(18) sun(i, 300) kiteColor = kiteColor.spin(60) dartColor = dartColor.spin(60) Thread.sleep(2500) } toggleFullScreenCanvas()

I think the program below should be easy to understand, well, at least considering that Penrose tilings are not the simplest recursive programs imaginable. But Kojo allows for doing this in a way that it is, algorithmically, completely transparent without the code 'getting in the way' at all.

/* Penrose tilings of the P2 type. There are two functions in this program that call themselves and each other recursively: halfKite and halfDart. Note that each function draws an equilateral triangle from the top, and that both functions always exit with the turtle having the same heading as when they entered. */ val Phi = (1 + math.sqrt(5)) / 2 // The golden ratio var kiteColor = green var dartColor = blue def halfKite(depth: Int, length: Double, mirrored: Int): Unit = { if(depth == 0) { // Base case: setFillColor(kiteColor) right(mirrored * 162) forward(length) right(mirrored * 108) forward(length / Phi) right(mirrored * 108) hop(length) left(mirrored * 18) } else { // Recursive case: we draw a half kite by means of // drawing two smaller half kites and a half dart. // // Move the turtle to the right position for the // half dart... right(mirrored * 162) hop(length / (Phi + 1)) left(mirrored * 54) // And draw it! halfDart(depth - 1, length / (Phi + 1), mirrored) right(mirrored * 54) hop(length / Phi) left(mirrored * 54) halfKite(depth - 1, length / Phi, mirrored) right(mirrored * 36) // Note that this half kite is mirrored with // respect to the larger one it is a part of. halfKite(depth - 1, length / Phi, -mirrored) left(mirrored * 162) hop(length) right(mirrored * 18) } } def halfDart(depth: Int, length: Double, mirrored: Int): Unit = { // As in the case of the half kite, we again // distinguish between a base case and a recursive // case. The recursive half dart is composed of one // half kite (mirrored) and a half dart (not mirrored). if(depth == 0) { setFillColor(dartColor) right(mirrored * 126) forward(length) right(mirrored * 144) forward(length * Phi) right(mirrored * 144) hop(length) left(mirrored * 54) } else { left(mirrored * 126) hop(length) right(mirrored * 18) halfKite(depth - 1, length, -mirrored) left(mirrored * 162) hop(length) right(mirrored * 126) halfDart(depth - 1, length / Phi, mirrored) right(mirrored * 126) hop(length / Phi) right(mirrored * 18) } } // The sun pattern can be drawn by drawing 10 half kites, // half of which are mirrored. def sun(depth: Int, length: Double): Unit = { repeat(5) { halfKite(depth, length, -1) right(36) halfKite(depth, length, 1) right(36) } } // Some scripting to call the sun function six times, // with a depth ranging from 1 to 6. // // After each call, a spin is given to the color of // both kite and dart. toggleFullScreenCanvas() repeatFor(1 to 6) { i => cleari() setBackground(black) setPenColor(black) setPenThickness(6 - i) setSpeed(superFast) right(18) sun(i, 300) kiteColor = kiteColor.spin(60) dartColor = dartColor.spin(60) Thread.sleep(2500) } toggleFullScreenCanvas()

I made a little demo out of it, called Roger.

You can download the demo here (my apologies, the source code is still much less elegant than it ought to be): http://joostwinter.net/crazywizardsoftware/roger/

…or alternately watch the video on Youtube: https://www.youtube.com/watch?v=FrruqBlXbcM

Enjoy!

var baseOne = 2 * math.sin(math.Pi * 54 / 180) var baseTwo = 2 * math.sin(math.Pi * 18 / 180) def triangleOne(depth: Int, length: Double, mirrored: Int): Unit = { if(depth == 0) { setFillColor(cm.green) forward(length) right(mirrored * 72) forward(length) right(mirrored * 144) hop(length * baseOne) right(mirrored * 144) } else { right(mirrored * 36) hop(length) left(mirrored * 144) triangleOne(depth - 1, length / baseOne, -mirrored) hop(length / baseOne) right(180) triangleTwo(depth - 1, length / baseOne, -mirrored) hop(length / baseOne) right(-mirrored * 36) hop(length / baseOne) right(180) triangleOne(depth - 1, length / baseOne, mirrored) hop(length * baseOne) right(mirrored * 144) } } def triangleTwo(depth: Int, length: Double, mirrored: Int): Unit = { if(depth == 0) { setFillColor(cm.blue) forward(length) right(mirrored * 144) forward(length) right(mirrored * 108) hop(length * baseTwo) right(mirrored * 108) } else { hop(length * baseTwo * baseTwo) right(mirrored * 108) triangleTwo(depth - 1, length * baseTwo, mirrored) hop(length * baseTwo) right(mirrored * 180) triangleOne(depth - 1, length * baseTwo, mirrored) left(mirrored * 36) hop(length * baseTwo) right(mirrored * 108) } } def decagon(depth: Int, length: Double) { clear() setBackground(cm.black) setSpeed(superFast) invisible() setPenColor(cm.black) left(90) hop(length) right(180) repeat(5) { triangleTwo(depth, length, 1) triangleTwo(depth, length, -1) right(72) hop(length * baseTwo) left(36) hop(length * baseTwo) left(108) } } clear() toggleFullScreenCanvas() var depth = 0 repeat(7) { decagon(depth, 400) depth = depth + 1 Thread.sleep(3000) }

My compliments to the Kojo devs for creating an environment that makes it surprisingly easy to do things like this…

In today's age, lots of us believe there is nothing else but contemporary technology that may ensure the general evolution of the youngsters, but it is not at all true. A drawing item called the Coloring pages may also ensure the evolution of the kids and that too quite easily.

As an adult, there are a lot of anxieties and thoughts in the brain of an individual. There are many and could have a negative effect on your own life. The coloring pages make out the child in an adult, and it helps in creating the things as favorable. With positive thinking, unwanted ideas are taken from the mind of an adult.

Child development is composed of developmental stages or milestones. Among the most crucial developmental activities is to form a personality which means to be stable and prepared to handle the challenges. While kid is engaging coloring activity he or she is concentrated and relaxed. This gives a child a chance to calm the mind, put aside all the burdening thoughts and make some space for pleasant emotions. If a child uses coloring pages frequently, this coloring task can become a self - soothing technique which is quite essential for challenging situations. Among other approaches coloring books are fun and imaginative way yourself comforting.

While coloring in the pages, the grasp of these children will be improved on the writing tool. There should be a holding of the tool in their children's hands. There will be routine practice through the kids before going to school. It will improve the strength of the hand and enhances their children's focus. There ought to be an involvement of habits among preschoolers.

It's perfect for your kids to make them engage in coloring sheets for creating them understand about the leaning. It is possible to create them color different alphabets and pictures of things and creatures; this is going to enable them to get familiarized with things that are unique in a simpler way. Making children learn about various things is necessary as they might fall short in studying. Coloring sheets can come to create them learn about items in a way that is lively.

Every person has a fixed sequence or colors set in his thoughts; it will create the feeling of creating his own sort of color arrangement. Thus, the child will certainly get to learn concerning the color schemes used in a variety of items such as the amount of colors in the rainbow and others.

• Dynamic typing means less help in finding bugs; risk of lower ambition
• No ''typing dialog'' with a compiler means less conceptual learning
• Non-explicit types in function defs is less efficient when learning abstract thinking
• Indentation syntax with silent begin-end can make nested blocks obscure to beginners
• No explicit variable declaration can lead to very hard bugs also for non-beginners
• Refactoring is more risky, hence discouraging -> bad for step-wise problem solving
• Not excellent at object orientation
• Not excellent at functional programming

I have no systematic empiricism behind the above hypotheses but I have some anecdotal evidence that suggest that the above list might be important to address when considering Python.

//Bjorn

PS: Would like to quote stackoverflow survey One out of every 200 is hard of sight.

Please let me know if this is something that interests you.

Tout fonctionne à merveille.

You can get Java 8 from Oracle, IntelliJ, or from Ubuntu repos.

/L

Exception in thread "main" java.lang.ExceptionInInitializerError
at net.kogics.kojo.lite.DesktopMain.main(DesktopMain.scala)
Caused by: java.lang.RuntimeException: classloader (jdk.internal.loader.ClassLoaders$AppClassLoader@255316f2) is not a URLClassLoader
at scala.sys.package$.error(package.scala:27)
at net.kogics.kojo.lite.DesktopMain$.<init>(DesktopMain.scala:23)
at net.kogics.kojo.lite.DesktopMain$.<clinit>(DesktopMain.scala)
… 1 more

Thank you for your hard work.

I see that the interface is translated in Italian but the exaples not.

I'm using kojo 2.4.12 for Linux - and have access to a not blleding edge computer.

TIA and Regards

Carlo D.

I am impressed by your project. I would wish Kojo to be used in every school.

Thanks to Lalit.

I have another question.

I am a math teacher in senior high school. In Kojo, Would it be possible to script number theory, mathematical modeling and so on?

For example, try this script:

Mw.clear()
Mw.hideAlgebraView()
Mw.showAxes()
Mw.variable("m", 1, -5, 5, 0.1, 50, 50)
Mw.variable("c", 0, -2, 2, 0.1, 50, 80)
Mw.evaluate("y = m x + c")

To see more examples, look (in the script editor) at the scripts for Help -> Kojo Overview and Samples -> Math Learning Modules -> Solving Linear Equations (run these scripts, and then search for Mw. in the script editor)

Code completion on the Mw object (type Mw. and then Ctrl+Space) will show you what's available for geogebra interaction.

Or you can look at the Mathworld class (of which the above Mw is an instance) to see what's inside in more detail:
https://github.com/litan/kojo/blob/master/src/main/scala/net/kogics/kojo/mathworld/MathWorld.scala

Hope that helps. Feel free to ask more questions.

Here is one of many guides on the net on how to do that:
http://www.androidauthority.com/crouton-turn-your-chromebook-into-far-more-than-a-glorified-web-browser-663044

The you install Java with this terminal command in your Ubuntu subsystem:

sudo apt-get install default-jdk

And then install Kojo as described for Linux on the Kojo download page. And ready to go!

BTW: This means that the sysadmin of your school should support your very important pedagogical ambitions in allowing your students to do "real" programing! :)

Hope this helped?

Good luck!

Yes, it is possible but requires that you enable developer mode, and you then can install crouton via commands in a terminal window as explained here:

https://www.howtogeek.com/162120/how-to-install-ubuntu-linux-on-your-chromebook-with-crouton/

After that you can install openjdk using this command in terminal:

sudo apt-get install openjdk-8-jre

and then download and run the kojo jar-file from terminal using this command:

java -jar xxx.jar

where xxx.jar is replaced by the name of the downloaded kojo jar-file from here:
http://www.kogics.net/kojo-download

If you have problems, your IT-department should be able to help you with the installation.
Good luck!
/B

DISPOSE_ON_CLOSE is defined in WindowConstants. JFrame implements WindowConstants, but DISPOSE_ON_CLOSE is not visible via JFrame in Scala (can't remember why off the top of my head).

import java.awt.Graphics import java.awt.image.BufferedImage import javax.swing.JComponent import javax.swing.JFrame val frame: JFrame = new JFrame("Fractal") frame.setSize(640,320) frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE) frame.setVisible(true)

Results in:

Error[9,39]: value DISPOSE_ON_CLOSE is not a member of object javax.swing.JFrame

I realise Kojo isn't necessarily meant to be used in this way, but for my better understanding, I am curious why DISPOSE_ON_CLOSE doesn't show up!

Will investigate as soon as I get access to a high DPI monitor. What's the DPI/Resolution on Surface Pro 3?

- Lalit

println(3.5*9.4+7/5) // Returns 33.9
println(3.5*9.4+7.0/5) // Returns 34.3 which is the correct product!
println(3.5*9.4+7/5.0) // Also returns 34.3 which is also correct!

So it appears that the 7 isn't being converted into a float. I can live with this bug, but just wanted to let everyone know that to be on the safe bet not to mix floats with integers until this gets correct. Take care now and have a good day!

Following "Expressions" section under the Scala tutorial, which is under Kojo's Help menu and ran the expression 3.5*9.4+7/5, which returned 33.9, I've repeated tried this expression using both Windows 7 calculator and Google search and the number I am getting from them is 34.3, which means either Kojo has a problem or the world as a problem. I have also tried just running it like this: println((3.5*9.4)+(7/5)), but again the result Kojo returns is 33.9. Perhaps I do not understand how the "order of operation" Kojo is performing, but I've tried it several ways got different results of course, but never got 33.9. Please look into this issue and let me know whether I am not understanding something or if there is a bug in Kojo. I really think Kojo is a great system overall, but if it's a calculation bug then it needs to be address. Thanks and have a great day!

A similar looking problem was reported here: https://groups.google.com/forum/#!topic/kojo-dev/u1jbahCiu-0

I will update that thread.

Thanks,
- Lalit

The hang was caused by Java Ayatana (evidenced by the "Picked up JAVA_TOOLS_OPTIONS" line above).

Adding this to the Kojo launch script corrected the problem:

unset JAVA_TOOL_OPTIONS

On the console, I see this:

./kojo
Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar
[INFO] Running first Kojo instance with args: []
[INFO] Java Home: /opt/jre1.8.0_45
Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=32m; support was removed in 8.0
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=256m; support was removed in 8.0
[INFO] Logging has been redirected to: /home/daddy/.kojo/lite/log/kojo0.log

Exception: java.lang.NullPointerException thrown from the UncaughtExceptionHandler in thread "AWT-EventQueue-0"

The above is for the Oracle JRE for Java 8, but there are only slight variations with other versions. The NPE at the bottom appears in all cases, and I suspect that it's at the root of the problem.

In the log, I see only a listing of the system properties, followed by this, which mirrors what I saw in the console:

[Sat Jul 11 22:33:53 EDT 2015, CodeExecutionSupport] SEVERE: stderr> Exception in thread "AWT-EventQueue-0"
[Sat Jul 11 22:33:53 EDT 2015, CodeExecutionSupport] SEVERE: stderr> Exception in thread "AWT-EventQueue-0"

Since there is no stack trace attached to the exception, I can't even venture a guess as to what the problem could be.

PS. From now on, messages on this forum will be cross-posted to the Kojo-User or Kojo-Dev google group.

Thanks for your concrete answers.

You're welcome.
So, things look under control now?

Good to know about your plans!

I will use the english version of Kojo during the first weeks in the first programming course in our media informatics program for teaching imperative programming.
Besides that we will use the german Kojo variant on 13th of june for short kids programming courses during the Berlin "Long Night of Sciences".

as from monday I will teach a full student group of 48 persons using Kojo.

What kind of class will this be? Computer science? Software engineering? Kojo visual programming stuff?

1) For what do we need the ~/.kojo/lite/libk directory?

Any jar in that directory will be on the classpath for scripts run within Kojo. So if you want to play with a third-party lib in Kojo, you can put its jar in the libk directory. By default the libk directory is empty.

2) As we don't have a ~ directory on Windows, is it taken from the environment variable
USERPROFILE (Windows user home directory) or the Java system property -Duser.home?

def homeDir = System.getProperty("user.home")

3) Would it work to collect the files from ${user.home}\.kojo\lite\libk by the same batch
script?

Yeah, that should work fine.

4) If so should I collect only .jar files from this directory?

Yes.

BTW: Where should I report issues? Here or on https://code.google.com/p/kojo/issues/list

Google code is getting phased out. Please report issues here:
https://bitbucket.org/lalit_pant/kojo/issues

1) For what do we need the ~/.kojo/lite/libk directory?

2) As we don't have a ~ directory on Windows, is it taken from the environment variable USERPROFILE (Windows user home directory) or the Java system property -Duser.home?
This is important as on our installation we have a separate area for each user, to which points only -Duser.home.

3) Would it work to collect the files from ${user.home}\.kojo\lite\libk by the same batch script?

4) If so should I collect only .jar files from this directory?

BTW: Where should I report issues? Here or on https://code.google.com/p/kojo/issues/list

Thanks again,
Christoph

Indeed, net.kogics.kojo.lite.DesktopMain actively works to disallow multiple instances. You can use net.kogics.kojo.lite.Main. That should work fine, other than a couple of limitations (the environment variable KOJO_CLASSPATH and the jars in the ~/.kojo/lite/libk directory will not be on the Kojo instance's classpath). You can ignore the connection exception.

Let me know if you run into any problems with this approach.

/L

C:\Program Files (x86)\Kojo2\lib>java -cp ;AppleJavaExtensions.jar;autocomplete.jar;docking-frames-common.jar;docking-frames-core.jar;geogebra.jar;geogebra_algo
s.jar;geogebra_cas.jar;geogebra_export.jar;geogebra_gui.jar;geogebra_javascript.
jar;geogebra_main.jar;geogebra_properties.jar;group-panel.jar;h2.jar;httpunit.ja
r;image-filters.jar;jdi.jar;jfugue.jar;jl1.0.1.jar;jlatexmath.jar;js-1.6R5.jar;j
ssc.jar;jtidy-4aug2000r7-dev.jar;jts.jar;kojo2.jar;piccolo2d-core.jar;piccolo2d-
extras.jar;rithica.jar;rstaui.jar;rsyntaxtextarea.jar;scala-actors.jar;scala-com
piler.jar;scala-library.jar;scala-parser-combinators.jar;scala-reflect.jar;scala
-swing.jar;scala-xml.jar;scalariform.jar;table-layout.jar net.kogics.kojo.lite.D
esktopMain
[INFO] Running > first Kojo instance with args: []
[INFO] Connecting (via RMI) with args: [] to already running Kojo instance
[INFO] Kojo Launcher Done.

Is there perhaps a command line option for Kojo to avoid connecting to an already running instance?
In our lab all students have their own account, but as they are running on the same server there could be a port conflict.

we have a Windows Terminal Server at Beuth University of Applied Sciences. Students log into it from client computers.
Only the first one starting Kojo by the Start menu succeeds. For all subsequent trials we only see a second-lasting hourglass, which diappears without a message. After exiting the first Kojo instance, another instance can be started.
As we do not know this behavior from other Java applications we suppose the little kojo.exe to be guilty.
In the Kojo2\bin directory there is a shell script for starting Kojo. It collects all .jar files from Kojo2/lib.
Do you have an equivalent script as Windows batch file for trying a workaround?
Or how could we diagnose, why only the first Kojo instance can start?

Thank you very much,
Christoph

kojoInterp - the scala interpreter
pcompiler - the scala presentation compiler
compiler - the scala compiler

You can use these to interpret code, and do reflection etc. These should be used from the default Kojo thread (and not from threads that you create in your script). Kojo also has a builtin interpret command that can be used from any thread.

All of this is meant to be used only by power users!

1. Check your Kojo version. The file used to install Kojo should have been KojoInstall-2.4.03.exe

2. Open up a command prompt, go to C:\Program Files\Kojo2\bin, and run kojo.exe. See what error message you get.

Let me know what you find.