Scratch

what-the wrote:

Cool. It looks like the broadcast and wait block.

Set variable to X
Broadcast "Jump" and wait



When Jump recieved
Change Y by 10
Wait 0.1
Change Y by -10

Problem with Broadcast and Wait is that parameters and return values are passed using global variables.  If several different sprites try to use the same signal, it can be quite a mess.

johnm wrote:

Fullmoon: The evaluator currently depends on the fact that all of the built in reporter blocks are atomic operations. They don't contain loops or "wait" operations, and they can't cause a thread switch. Thus, all argument expressions can be recursively evaluated inline; the evaluator does not need to save and restore state during argument evaluation because no thread switches can occur. In contrast with built in reporters, a user-defined reporter may contain an infinite loop or a block that does a "wait", thus forcing a thread switch. The mere possibility of a thread switch would force the Scratch argument evaluator to save and restore state for every expression it evaluates, just in case that expression causes a thread switch.

Of course, it might be possible to optimize the evaluator to avoid the expensive case when it can (although even detecting the fast cases would add some overhead). But my bigger objection to user-defined reporters is precisely that they can introduce a thread switch in any block that takes an argument. Although most users don't need to worry about when thread switches occur, Scratch currently allows thread switches only on "wait" blocks and at the end of loops. This design prevents many of the concurrency errors that can occur in other languages, and it works extremely well. User-defined reporters introduce potential thread switches at unexpected places, thus making concurrency errors more likely.

Concurrency errors are extremely difficult to diagnose and debug, even for the most experienced programmers. (I've sometimes spent days or even weeks looking for a single concurrency error.)

The combination of decreased performance and the potential to introduce concurrency errors makes me very reluctant to introduce user-defined reporters in the first release of Scratch 2.0. I don't rule them out for a future release, but I'd like to see how the Scratch community responds to the ability to define command blocks first. One step at a time.

-- John

I am quite new to Scratch, but quite interested in this discussion.  What about a compromise, where custom reporters could be built only from already existing reporters, with "input" variables, kind of like an expression with variables in basic algebra.  It would be much weaker that allowing any commands in custom reporters, but as far as I understand, it would eliminate the problems you mention above.

mcguire wrote:

Will Scratch 2.0 work with Picoboards and WeDo kits? - I have both.

Yes.

Yup.Some things and glitches hit the ceiling in scratch very easily,and using MESH is hard.BYOB also has a "share this sprite"feature,allowing people to send sprites to another MESH user.Incorporate that too 

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Last edited by Paddle2See (2011-07-08 20:34:06)

This Will Be Epicz

Hopefully there can be some real java in it.

System.in.println("Hopefully!")

why not make a block for switchin a costume while it plays the sound i know horrible idea 

<when green flag clicked><forever if>board and want to make your own scratch block?<wait( several )months><go to[ scratch 2.0 ]

well, i think about adding colour, and combo boxes input into customized blocks.
And in this new version the blocks we made will be always in the "variables" tab?
And variables haves lists,blocks. So i think it should be now called "custom"
or something like that. 
But it would be awesome!
I Hope Jens doesn't get Jealous with this lol

scimonster wrote:

lu9 wrote:

I Hope Jens doesn't get Jealous with this lol

Jens is wholeheartedly supporting this!

Heres a block example

<real time = [] hours>

<real time = [] minutes>

<real time = [] seconds>

<real time seconds>

<real time minutes>

<real time hours>

All of these are based on the real time (or the time on your PC clock). And can be used for projects involving clocks, digital time and calenders! I hope it gets used in Scratch 2.0!

My my my, i cannnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnot wait for Scratch 2.0.
All i have to say is, you HAVE to include custom blocks.
Im not sure if it is too similar, but the ability to just program it or use the blocks would be good with the option to save a piece of program as a custom block.
Cant wait for 2.0!

this is gonna be awesome!!!!!!!!!!!!!