Scratch

Maybe for sprite masking, you could have a [set mask to [costume]] block.

floppy_gunk wrote:

Maybe for sprite masking, you could have a [set mask to [costume]] block.

We won't need a new block.  In the new 3.1 world, we would just add MASK to the set of attributes, and then you could use the plain old SET block.

Way back when we started this project, and I found out about Panther, I thought "these are really cool features but there are too many blocks!"  I think we have now solved that problem, at least for sprite-related things. 

Feeling like the dumb kid again...

I'm rewriting the games of some of my kids in BYOB, to see if I can learn anything from it, and also if I can TEACH anything...  I want to test whether a sprite has children.  I've tried this three ways: 

wait until ((attribute -> children) of spriteX) = 0

wait until (length of ((attribute -> children) of spriteX)) = 0

if (not (attribute(children) of spriteX))

The first two tests are always true.  The third gives a syntax error, and the script gets highlighted in red.  Clearly I don't really understand what the 'children' attribute is -- which I guess is one question.  And a second is, how should I test for the existence of clones/children? 

More questions on their way...

nXIII wrote:

bharvey wrote:

IMHO what you really want is the ability to right-click an input name orange blob and have a "set type" option that opens the same dialog as the long form Block Editor input name/type one.  Then you could just choose the multiple inputs option.

No. The "multiple inputs" option is simply syntactic sugar for calling the procedure with a LIST block in an argument (the exception is unevaluated inputs, which are also syntactic sugar for THE SCRIPT or THE BLOCK (which is syntactic sugar for THE SCRIPT and RETURN)). I want a closure which can be called with a variable number of arguments and which knows the amount of arguments it was called with. The solution: a list of the arguments. This is not the same thing as an argument which is a list, which could be checked with an IF statement at the beginning of the closure.

This is a handy feature in similar closure-based languages...Javascript has the arguments object available from within every function, and in AS3 you can specify ...args instead of parameters in the method signature to obtain a list of arguments instead.

two more attribute questions:

- where does the 'heading' attribute in jens's breakout game come from? and
- what's the 'anchor' attribute? 

sorry if this has all been covered, I've been busy for the last couple of weeks.

Another simple game that's stumping me, this time online at:

http://www.mercey.org/clinton/matthews_devil.ypr

Here I have two issues, perhaps related, both involving the spawning of 'bullet' clones to enemy ships in a space battle game.   I'm using Jens' "tell (ask OBJECT for CLONE) to ACTION [" trick to get a clone to execute certain steps when it's created.  In my case it just says:

tell (ask EVIL BULLET for CLONE) to [
go to object MYSELF
show
] (do I have the caps all wrong? sorry if I do!)

This doesn't work, so I tried setting a script variable a first to object MYSELF and then to the (object MYSELF) block, and then
go to a

Neither of these was successful.  I need the reference to "myself" so that I can clone the enemy spaceship later on in the game; and in any case, the 'go to' block doesn't permit 'go to SpriteX' unless you're in a non-spriteX sprite. 

(2) I'm realizing how much I rely on "when green flag clicked" scripts for permanent behaviours of sprites.  With clones this doesn't work, and I really miss it.  I'm not sure what the best replacement is when clones are added at an arbitrary point in the game.  In Jens' breakout game, the bricks are all cloned at once, so you can send a signal to them all once they've been created.  In my very simple game, the bullets are created all the time, and they need to be run in a forever loop -- or anyway a repeat until loop -- which should probalby be spawned off from the script that created them.  I guess I could define a brick that governed the bullet's movement, and put it in the "tell the clone to" c-shaped brick; but that would still stall the bullet-creation script until the current bullet had been extinguished.  It would be great if there was a "when created" or "when I clone myself" brick, or, better I guess, if I could figure out how to create such a brick myself. 

thanks agian!
matt

gardenhackers wrote:

wait until ((attribute -> children) of spriteX) = 0

Like most programming languages, excepting afaik only the purely functional ones such as ML and Haskell, BYOB uses applicative order evaluation, which means basically that expressions are evaluated from the inside out.  For example, if you say

[2 + [3 * 4]]

the plus function gets 2 and 12 as inputs; it doesn't know how the 12 was computed.  The only exceptions to this rule are the special forms; that's what's special about them.

So, in particular, when you use an OF block, its two inputs are evaluated before BYOB does the OF function itself.  In even more particular, when you say

[[ATTRIBUTE <whatever>] OF <whatever>]

the very first thing that happens is the evaluation of the ATTRIBUTE call, which reports the value of the chosen attribute of this sprite!  This isn't what you want; you want the OF block to know which attribute of some other sprite you're trying to find out.

I'm like the sort of academic who only ever has one idea in his or her entire career, and keeps writing slight variations of the same paper over and over -- except that in my case, the one idea isn't even mine.     The idea is first class procedures and maybe an even better analogy is the one about the guy who only has a hammer; my instinctive solution to every problem is to encapsulate something in a procedure-as-data.  So, the value of

ATTRIBUTE <CHILDREN>

is a list, but the value of

THE [ATTRIBUTE <CHILDREN>] BLOCK

is an encapsulated request for someone's children.  That's why, as 14God says, you have to put the ATTRIBUTE block inside a THE BLOCK block.

But, notice that OF will report the other sprite's version of the ATTRIBUTE block.  You then have to call that block.  So what you want is the mouthful

[[LENGTH OF [CALL [[THE [ATTRIBUTE <CHILDREN>] BLOCK] OF [OBJECT <whatever>]]]] = 0]

Luckily all those nested brackets turn into colorful self-delimiting blocks in a graphical language.  And the 3.1 version of the tools project will have a block

ASK <object> FOR <Reporter>

and since that slot is Reporter-type instead of a dropdown list, it has grey-border behavior and you don't need an explicit THE BLOCK nor an explicit call to CALL (the ASK block does the CALL and the OF for you).  So it'll be

[[LENGTH OF [ASK [OBJECT <whatever>] FOR {ATTRIBUTE <CHILDREN>}] = 0]

where the {braces} indicate a grey border.

fullmoon wrote:

and in AS3 you can specify ...args instead of parameters in the method signature to obtain a list of arguments instead.

Yeah, and in BYOB you can specify "args..." instead of parameters to do the same thing!  What am I missing here? 

bharvey wrote:

gardenhackers wrote:

wait until ((attribute -> children) of spriteX) = 0

L
But, notice that OF will report the other sprite's version of the ATTRIBUTE block.  You then have to call that block.  So what you want is the mouthful

[[LENGTH OF [CALL [[THE [ATTRIBUTE <CHILDREN>] BLOCK] OF [OBJECT <whatever>]]]] = 0]

Luckily all those nested brackets turn into colorful self-delimiting blocks in a graphical language.  And the 3.1 version of the tools project will have a block

ASK <object> FOR <Reporter>

and since that slot is Reporter-type instead of a dropdown list, it has grey-border behavior and you don't need an explicit THE BLOCK nor an explicit call to CALL (the ASK block does the CALL and the OF for you).  So it'll be

[[LENGTH OF [ASK [OBJECT <whatever>] FOR {ATTRIBUTE <CHILDREN>}] = 0]

where the {braces} indicate a grey border.

OK, I think I get it now. I'll go give it a try.  Thanks a bunch -- super helpful!

bharvey wrote:

gardenhackers wrote:

tell (ask EVIL BULLET for CLONE) to [
go to object MYSELF
show
]

As I think you've worked out, the problem is about the scope of the "myself."  Anything inside that script is going to be run in the target sprite, not in the originating sprite.  Using a script variable inside the script, set inside the script to the result of a "myself" inside the script, doesn't help that.

It really helps if you understand that

TELL <obj> TO <script>

means

LAUNCH [[THE SCRIPT <script>] OF <obj>]

What you actually want (my version of TELL lets you do this; I haven't read Jens's project's code yet so I'm not sure about his) is

LAUNCH [[THE SCRIPT <script>] OF <obj>] WITH INPUTS [OBJECT <MYSELF>]

and then in your script, you say  GO TO < > leaving an empty slot into which the argument value (a sprite, in this case) will go.

I'm realizing how much I rely on "when green flag clicked" scripts for permanent behaviours of sprites.  With clones this doesn't work, and I really miss it.

Isn't this the purpose of the TELL [CLONE] TO ... idea?

gardenhackers wrote:

it doesn't seem to be working.

Since we're talking about a list, not a text string, you have to use the red LENGTH block in the Variables palette, not the green one in Operators.  I agree that this is an annoying confusion, but we inherited it from Scratch.

bharvey wrote:

What you actually want (my version of TELL lets you do this; I haven't read Jens's project's code yet so I'm not sure about his) is

LAUNCH [[THE SCRIPT <script>] OF <obj>] WITH INPUTS [OBJECT <MYSELF>]

and then in your script, you say  GO TO < > leaving an empty slot into which the argument value (a sprite, in this case) will go.

sorry, I screwed up the posting where I meant to respond to this.  This works great, and thanks also for the clarification about launch vs. run.  I don't see how, in the block creation interface, I would create the TELL [sprite] TO [action] c-shaped block in such a way as to enable the WITH INPUTS element for the included script.  Jens's does not seem to permit inputs -- it's just:

TELL [object] TO [action] [
LAUNCH (action OF object)

where action is a c-shaped input.  How do I translate an input to TELL into an input to the LAUNCH block it contains?   I knowthis is remedial, but I'm still having trouble iwth it.  Thanks again (and again, and again...).

See at : http://www.xleroy.net/ByobTuto/New/Thumbnails.html one project using TELL and OBJECT allSprites.