Scratch

bharvey wrote:

Hot off the presses: a Greek translation by
Nektarios Moumoutzis.  Download it and add it to the locale folder.

That's all Greek to me. 
Actually, I'm not downloading it, because I only have like 6GB left on my C: drive ( ), so I'm trying to clear up unneeded stuff, not add unneeded stuff. ^^

14God wrote:

OFF TOPIC:
Is it against Berkeley's policy to allow you to put a donation button on the BYOB site?

That's more on topic than how much disk space you have! 

We could probably accept donations to the university on the web site, and (if we had the technology set up) even direct them to our project.  We'd have to get several thousand dollars to do anything really useful with the money (namely, hire an undergraduate, or maybe buy Jens an airplane ticket).

We couldn't just pocket the money, though.

All in all, I think the small amount of money involved wouldn't be worth the possibility of someone seeing it as a barrier to using BYOB (e.g., because they wouldn't want to see their students feel under pressure to contribute).

Maybe someday you can take me and/or Jens out to dinner. 

P.S.  You young whippersnappers who think 4Gb isn't much disk space don't know how lucky you are!  Why, when I was your age we had to read the bits on the disk with a magnifying glass!

Last edited by bharvey (2011-06-01 16:40:34)

When I click the 3.1.1 link (Mac) I get

Server not found
Firefox can't find the server at byob.berkekey.edu.

bharvey wrote:

Maybe someday you can take me and/or Jens out to dinner. 

Unlikely, I'm not much for traveling. Not to say that I'm a Scrooge or a Hermit    I would definitely work for you guys (for free) if I knew Java script, which I don't... for now.

14God wrote:

BUMB, we aren't on the front page!

Now you are LOL. 14God and God4all! Now isn't that strange? 

14God wrote:

whats the progress on Snap?

Umm.  Jens is working on the GUI part, and, being Jens, will be finished first.     Fullmoon and nXIII are working on implementing the primitive blocks.  I have a team of four Berkeley students working on the evaluator -- probably too many, because I didn't get any progress reports while I was in Boston.     I'll try to get on top of that now that I'm home and finally unpacked.

Btw, I had interesting discussions with members of the S.T. while I was there.  No big news on Scratch 2.0; right now they're mostly focused on the Web aspects of the project rather than on new features of the language.  But, thinking ahead, they're interested in capturing the new AP CS Principles audience, just as we are, and that might encourage them to raise the ceiling somewhat down the road.  NO PROMISES, but I think I made a convincing case that custom reporters and first class lists are the very least anyone would need to decide to teach the course entirely in Scratch.  They didn't promise anything; as always, they're very cautious about making sure the design of new features will fit in well with their original goals.  But they didn't seem to have strong objections about those two things.  First class procedures and sprite inheritance were much harder sells!  Those definitely open big cans of worms; I couldn't really argue that people who didn't want to use those features wouldn't notice them.  OTOH, I'm hoping a year from now to have hard data about how well high school students learn to use first class procedures, and if the trials go well, I'll have more convincing arguments to make in next year's summit meeting.     I had a long talk with John M. about the technical details of inheritance in BYOB.  (For example, our version relies on first class blocks, and we talked about how it might be done without that, which would arguably make inheritance more understandable to beginners even if you do have lambda also.)  I also made a pitch for some of the less central UI improvements (imho) in BYOB, such as zebra coloring.  So, who knows, maybe some of those will find their way into Scratch 2.1 or 2.2 eventually.

bharvey wrote:

scimonster wrote:

MathWizz wrote:

The links are broken. 

BYOB site is down. 

It works for me.  If you guys are still having trouble, could you send me a screenshot or a more detailed report on what happens when you try it?

henley wrote:

(screenshot)

Oh!  You have an old link.  It's http://byob.berkeley.edu/BYOB_3_1_1_110 … hanges.zip for the latest version.  Where did you find the link you clicked?

Thanks for posting the screenshot!

Last edited by bharvey (2011-06-09 11:28:40)

14God wrote:

I think recursion is in a sense far more difficult to learn because it is harder to mentally track.

That's really what I think, too, but pretty much every CS teacher in the world seems to disagree with me.  But it's complicated because in other languages there are really three levels of understanding HOFs involved and BYOB sort of mixes up the first two:

1.  Being able to use prebuilt higher order functions (e.g., MAP) with named functions as input.  So, in Scheme, something like

    (map square '(7 8 1) )    ==>  (49 64 1)

2.  Being able to use prebuilt HOFs with functions created on the fly using lambda:

    (map (lambda (x) (+ x 3) ) '(7 8 1) )    ==>   (10 11 4)

3.  Being able to write your own HOF.

I haven't ever really thought this through before in quite this way (so, take note, please, Jens, and tell me what you think about it), but the whole grey-bordered-input notation that people seem to find confusing is kind of my attempt to have something at that first level of understanding, so you could use MAP without using THE BLOCK explicitly.  Level 2 is where THE BLOCK (our version of lambda) should come in, but in BYOB, unlike Scratch, there's really no such thing as "the name of a block" distinct from the block itself.  If you make a SQUARE block, you still have to say THE [SQUARE ()] BLOCK or the grey-border equivalent to use it as input to a HOF.

It matters because level 1 is the thing that I think anyone could understand easily, but the drawback of a visual language is that we don't really have a level 1.  A long time ago I tried to talk Jens into making the grey border come before the white halo as you move toward a procedure-type input slot, but for reasons I don't understand it was too hard to do it that way.  I think that would help move grey borders toward being a level 1.

But meanwhile, people essentially have to start at level 2, and I think that makes the whole business seem more arcane than necessary.

Thanks for prodding me into thinking this out!

... have them work on (fun) projects that you know will be almost impossible without BYOBs features

   You're a Trotskyite!  You've just reinvented the "transitional demand."  (Look it up in Wikipedia.) 

Funnily enough, I find recursion easy, but have no idea what this lambda stuff is about.

scimonster wrote:

I don't understand recursion.

Preface:  In my computer science books I explain recursion three times, three different ways, because different people seem to respond better to different ways.  So if you read the following and it doesn't help, please don't give up.  But do tell me which step loses you.

1.  The definition of recursion:  A procedure calling itself inside its definition.  In BYOB terms, that means a block whose script (in the Block Editor) includes the block itself.

2.  The purpose of recursion is to help solve the kind of problem that includes a simpler version of the same problem within it.  The canonical example is drawing a tree:



Do you see that (a) the whole thing is a tree, and (b) the red part is also a tree and the orange part is also a tree?  That's an example of a "problem that includes a simpler version of the same problem within it."

3.  So we're hoping that the script for TREE will be something like this:

draw the trunk (the blue vertical)
turn left
TREE
turn right
TREE

4.  That pseudo-script actually almost works, except for two things.  The first is that, if you think about the steps in that script, it's assuming that after the first call to TREE (the one that draws the red smaller tree), the sprite is back at the bottom of the red tree, not up in the leaves somewhere.  So we have to add two lines to the script to ensure that that's the case:

turn left (back to the starting direction)
move back down the trunk

5.  The second problem with this script is that, as it stands, it'll keep trying to draw smaller and smaller left branches forever, so it'll never actually draw a right branch!  To fix this problem, we need a way to measure the complexity of the problem -- or, in this case, the depth of the tree, which is the number of line segments from a leaf down to the bottom of the (entire) tree.  So, the tree in the picture has depth 5; the red and orange trees each have depth 4.

A depth-1 tree is just its trunk.  So:



6.  A depth-2 tree includes two depth-1 trees:



7.  Once you see how to write TREE2, you could write TREE3 using it, and rhen write TREE4 using TREE3, etc.

8.  Instead of including the depth as part of the name of the block, we could have a single TREE block that has an input named DEPTH.  But (see point 5 above) we have to remember that a depth-1 tree is different from the others:



Okay, that's it for tonight.  Are you still with me?  Or, can you say where you don't follow the argument?  Thanks.

I couldn't understand the Church numerals PDF either. I could understand the concept perferctly, but I couldn't see how the given blocks were supposed to work.

bharvey wrote:

scimonster wrote:

I don't understand recursion.

Preface:  In my computer science books I explain recursion three times, three different ways, because different people seem to respond better to different ways.  So if you read the following and it doesn't help, please don't give up.  But do tell me which step loses you.

1.  The definition of recursion:  A procedure calling itself inside its definition.  In BYOB terms, that means a block whose script (in the Block Editor) includes the block itself.

2.  The purpose of recursion is to help solve the kind of problem that includes a simpler version of the same problem within it.  The canonical example is drawing a tree:

http://byob.berkeley.edu/Tutorial3/simplecolors.gif

Do you see that (a) the whole thing is a tree, and (b) the red part is also a tree and the orange part is also a tree?  That's an example of a "problem that includes a simpler version of the same problem within it."

3.  So we're hoping that the script for TREE will be something like this:

draw the trunk (the blue vertical)
turn left
TREE
turn right
TREE

4.  That pseudo-script actually almost works, except for two things.  The first is that, if you think about the steps in that script, it's assuming that after the first call to TREE (the one that draws the red smaller tree), the sprite is back at the bottom of the red tree, not up in the leaves somewhere.  So we have to add two lines to the script to ensure that that's the case:

turn left (back to the starting direction)
move back down the trunk

5.  The second problem with this script is that, as it stands, it'll keep trying to draw smaller and smaller left branches forever, so it'll never actually draw a right branch!  To fix this problem, we need a way to measure the complexity of the problem -- or, in this case, the depth of the tree, which is the number of line segments from a leaf down to the bottom of the (entire) tree.  So, the tree in the picture has depth 5; the red and orange trees each have depth 4.

A depth-1 tree is just its trunk.  So:

http://byob.berkeley.edu/Tutorial3/tree1pic.gif

6.  A depth-2 tree includes two depth-1 trees:

http://byob.berkeley.edu/Tutorial3/tree2pic.gif

7.  Once you see how to write TREE2, you could write TREE3 using it, and rhen write TREE4 using TREE3, etc.

8.  Instead of including the depth as part of the name of the block, we could have a single TREE block that has an input named DEPTH.  But (see point 5 above) we have to remember that a depth-1 tree is different from the others:

http://byob.berkeley.edu/Tutorial3/base1tree.BMP

Okay, that's it for tonight.  Are you still with me?  Or, can you say where you don't follow the argument?  Thanks.

I got all that; the wiki explained it pretty well. LOL XD
Stuff like the MAP block is where I get lost, but that also uses lambada, which is in the same language as the most recent translation.