World: r3wp

Well, I modified the code from draw-controls.r in the script library 
to get this. It is more complex than I expected, 

Is it a reasonable way to do this sort of thing please?

pos1: 20x20  pos2: 80x0
view layout [
	scrn: box rate 0:0:0.1 feel [
		engage: func [face action event] [
			if action = 'time [
				scrn/effect/draw: copy []
				append scrn/effect/draw [line pos1 pos2]
				show scrn
			]
		]
	] effect [ draw [] ]
	s1: slider [
		ss1: to-integer (100 * get-face s1)
		pos2: (as-pair 80 ss1)
	]
]


Next step is to work out how to make the thing that moves leave a 
trail.

view layout [box: box effect [draw [line 20x20 80x20]] slider [box/effect/draw/3/y: 
to-integer value * 60 + 20 show box]]

To leave a trail, you could append to the draw block (without setting 
it to a new block each time, as you've done above), but that would 
mean your draw block would get very big over time.

So a better thing to do is to draw onto an image!, which serves as 
a cache of your previous draw commands. For this, you can use an 
IMAGE instead of a BOX, and use the DRAW function to draw permanently 
onto the image. (The IMAGE style is very similar to BOX, but its 
'image facet is set to an image! for us, ready to use.)

Oops! No it doesn't !  IMAGE does *not* come initialize its 'image 
facet with an image! for us! We need to create one for it...

view layout [my-image: image (make image! 100x100) slider [draw my-image/image 
reduce ['line 20x20 as-pair 80 value * 60 + 20] show my-image]]

Another way to write that is:

img: make image! 100x100
draw-blk: [line 20x20 80x20]

view layout [my-image: image (img) slider [draw-blk/3/y: value * 
60 + 20 draw img draw-blk show my-image]]

The difference being we are using another word (IMG) to reference 
the image!, and the draw block (DRAW-BLK) is not created new each 
time, it is reused. Only the third value in the draw block is modified. 
That could become significant with large draw blocks.

Thanks Anton, that looks a lot simpler. It is going to take me a 
while to digest your suggestions fully.   I want to understand it 
well enough to appreciate exactly how this works & where I can read 
the code to deduce locations of thing like box/effect/draw/3/y  for 
myself.   I have been hunting through the documentation but there 
is such a lot of it that I may have failed to look in the right place. 
Thanks.

I advise you to review each facet in the face object:

	print mold first system/standard/face

and compare with the slightly larger vid-face:

	print mold first system/view/vid/vid-face


(Note, here FIRST is being used to return just the words of an object!, 
without their values. If you just probe a face it will fill up your 
console...)

Once you find a specific facet you are interested in, you can then 
probe it to see its value:

	print mold get in face 'color  ; == 200.200.200


and you can do this, of course, with any face you make, such as the 
BOX above.

Thanks for the extra information.  I am slowly piecing it all together.

Hi, I have continued to re-read the documentation for REBOL, and 
appreciating it more as I understand a bit more.

Are there any puzzels I could try to write a solution to, in REBOL, 
that would be good for a beginner please?

There is a puzzles group, and the corresponding puzzles answers group. 
 However, I don't believe the puzzles are easy.

It is hard for me to judge how hard a puzzle might be. I have some 
ideas of what I want to program for my self, but I get stuck too 
quick, so I need to exercise my understanding in a context where 
I can have a good chance of success.

Definitely these puzzles aren't for beginners. But have you already 
had a look at the cookbook at http://www.rebol.net/cookbook? That 
might be a good start trying to understand some of the examples there 
and go on from there ...

Here's how you can get a cross-section of all the VID styles, examining 
the same facet (TEXT) for all of them:


 foreach [style face] svv/vid-styles [print [style mold face/text]]

As you can see, only a few have TEXT set by default.

(mhinson, that's for you.)

Here's a puzzle I posed (because I wanted a better answer). The ensuing 
discussion is excellent:
http://www.rebol.org/ml-display-thread.r?m=rmlCHQQ

And here's another one. In both cases, there were excellent procedural 
solutions and parse-based solutions.
In both cases, the parse-based solutions were much faster:
http://www.rebol.org/ml-display-thread.r?m=rmlPCJC

Thanks Sunanda. I will have a go at it without reading any suggestions, 
then learn what I did wrong :-)   If I am not back in a week, send 
a search party.

That's kind of what I did.....First had the operational problem; 
then solved it with a procedural hack; then asked the experts to 
impress me. They did!

Good luck

I have a plan, but I am stuck before that as I can't work out how 
to reference the value of a variable in a block.
aa: 1  bb: 2  cc: [aa bb]  print first cc

I want it to print 1, but however I arange the brackets I can work 
out how to do it..  I know this is very basic, sorry.

You can do one of two things:

aa: 1 bb: 2 cc: reduce [aa bb] print first cc

aa: 1 bb: 2 cc: [aa bb] print get first cc

the get  function evaluates a word and returns its value, 

the reduce function evaluates a block and leaves all the results 
within the block

(to complement henrik's example)

in rebol, words are both litteral values and references to values. 
  a word can also be unbound, in which case it essentially refers 
to no value.

and dont kid yourself, this isn't as basic as you'd think  :-)  
I still get bit, even fater years of rebol experience  :-)

oops  fater=after...  darn I'm really infected by the reichart keyboard 
syndrome  ;-)

Thanks, that has bought me back to the position that there is an 
outside chance I can solve this. 

What was getting me was that sometimes print reduce cc/1 would return 
an interger & sometimes a word & I couldn't work out why.

storing the integers in the block  as suggested  cc: reduce [aa bb] 
makes it work right through my code. :-)  Thanks.

This is my first crack at it...  
blob: [1 23 25 26 27 26 24 2 13 56 57 58 59 34 23 7]
score: copy 0
top-score: copy [0 0]

repeat i (length? blob) [if/else ((blob/(i) + 1) = (blob/(i + 1))) 
[
	score: score + 1
	if (score > top-score/1) [
		top-score: reduce [score i]]
	][
	score: 0
	]
]
probe top-score

print rejoin [(blob/((top-score/2) + 1 ) - (top-score/1)) "--" blob/((top-score/2) 
+ 1 )]


Reading on I see it being solved with parse.. I will try to understand 
that now if I can...  I also realise my solution would be better 
if the repeat loop was 1 less than length. However running over the 
length seems to have no bad consequence in this case.  Thanks for 
the chalange & help.

It works, and it is more compact than my original -- so lots of bonus 
points there.


It's worth reading on to look at some of the other procedural solutions, 
and Joel's analysis. That'll give you some good tips on how to solve 
a problem like this using  REBOL's data manipulating tools.

The parse solutions then take it to another level :-)

I still dont feel up to the parse version of the first puzzel, so 
I have had a go at the first part of the second puzzel.  I think 
I am a bit confused about where to use var: 0 
var: copy 0

I have also got a bit mixed up with the use of global variables which 
I know is bad.  This is the code, which now dosnt seem to work since 
I put the variable initalisation inside the compress function, and 
tried to pass the variables to the function.. Dont laugh, but this 
is about 3 hours work.

raw-data: [1 2 3 10 11 99 101 2000 2001 2002 2003 2004]

sequence-break: func [count store result][
	if/else (count > 1) [
		append result to-pair rejoin [store "x" count]
		count: 1
	][
		append result store
	]
]


compress: func [raw-data][count: 1 store: reduce raw-data/1 result: 
[]
	repeat i ((length? raw-data) - 1) [
		if/else ((raw-data/(i) + 1) = (raw-data/(i + 1))) [
			count: count + 1 
		][
			sequence-break count store result
			store: reduce raw-data/(i + 1)
		] 
	] sequence-break count store result
]

probe compress raw-data


I am happy if my code is functional & easy to maintain at the moment. 
 I will never be an application developer but using small bits of 
code to increase personal productivity is IMHO a very worthwhile 
thing to try and do.

I'll just note that you should use either instead of if/else  ... 
the later is deprecated and slower

so it would be:

either (count > 1) [

you'd use  var: 0  since 0 (an integer!)  is not a series type of 
data.

I don't have the time right now to debug the whole of it though... 
 ':-/

Thanks for the tips, so either exactly replaces if/else

and I need to initalise series types with var: copy [] but not other 
types.   

These tips are great.. I just need to study it more & I shoud find 
my own bugs (and probably remember them too)  Thanks very much

Object types are reference types too, but you usually need to do 
other tricks instead of COPY with them.

Many thanks for taking an interest in my newbie fumblings.

We were all newbies once! And we all are again every time we start 
learning something new.


I just remembered another puzzle/challenge I presented to the Mailing 
list, and got back a rich range of replies. This one is purely parse 
(including my first attempt), so trying it out, and then looking 
at others' code can help understand parse. As with the other two, 
it is based on a real-world need, rather than being a textboox exercise. 
(You experience the results of all three puzzles whenever you browse 
wwwREBOL.org).

Good luck with this one too!
http://www.rebol.org/ml-display-thread.r?m=rmlGPGQ

And, just in case you had any more spare time in the next month, 
another one that really surprised me as being amenable to a parse 
solution:
http://www.rebol.org/ml-display-thread.r?m=rmlJNFC

Hi, thanks for the extra puzzles.


I have managed to write a version that works now, but I am frustrated 
because I cant understand how to keep variables local & pass them 
to my function & return the changed values back...  In previous programming 
experience I seem to remeber that the function header listed the 
variable names & types used localy, then the function was called 
with the variables of the right type in the right order.. I cant 
remeber how results were returned in that context.


I have been reading here http://www.rebol.com/docs/core23/rebolcore-9.html#section-3.5
but every way I try seems to stop the code working as expected.

raw-data: [1 2 3 10 11 99 101 2000 2001 2002 2003 2004]

sequence-break: func [][
	either (count > 1) [
		append result to-pair rejoin [store "x" count]
		count: 1
		reduce [count result]
	][
		append result store
		reduce result
	]
]

compress: func [raw-data][
	count: 1
	store: reduce raw-data/1
	result: copy []

 repeat i ((length? raw-data) - 1) [either ((raw-data/(i) + 1) = (raw-data/(i 
 + 1))) [
			count: count + 1 
		][
			sequence-break count result store
			store: reduce raw-data/(i + 1)
		]
	]
	sequence-break count result store
	reduce result
]

print compress raw-data

here is how to declare a local word using func

my-func: func [arg1 /local my-lcl][
	print arg1
	print my-lcl
]

my-lcl: "NOT"

my-func "YEP"

==
arg1
 
none

there are three other function! type building functions:
DOES
HAS
FUNCTION

look them up in the online rebol dictionary: 
http://www.rebol.com/docs/dictionary.html

you can also get help directly in the rebol console:

>> help does
USAGE:
    DOES body

DESCRIPTION:

     A shortcut to define a function that has no arguments or locals.
     DOES is a function value.

ARGUMENTS:
     body -- The body block of the function (Type: block)

(SPECIAL ATTRIBUTES)
     catch

you can also see its source, when its mezzanine code (standard rebol 
function written in rebol itself)

>> source does
does: func [

    {A shortcut to define a function that has no arguments or locals.}
    [catch]
    body [block!] "The body block of the function"
][
    throw-on-error [make function! [] body]
]

HTH !

Great, this will help a lot, thanks.

I am beginning to realise that just because I have found a way to 
create a function (e.g. func) that dosn't mean I have found ALL the 
ways to make a function.  This seems to be a common theme in REBOL 
& has caught me out before.


This is my interpretation of what you have said & what I have read, 
however it does not work so I am obviously misunderstanding the method.

;; I am expecting this to reverse the arguements by passing them 
to a second function, while keeping all the function variables local 
& just passing back the result.

func1: func [/local arg1 arg2][
	temp: arg1
	arg1: arg2
	arg2: arg1
	reduce [arg1 arg2]
]

funcA: func [/local argA argB][
	func1 argA argB
	reduce [argA argB]
]

probe funcA 2 3

>> probe funcA 2 3
[none none]
== 3
>>

As written, neither funcA nor func1 take any arguments - the variables 
listed are after the "/local" key that turns them into local variables 
initialized to none

the ==3 printed is because 

>> probe funcA 2 3


doesn't grab any argument, so it evaluates funcA, evaluates 2, evaluates 
3 and the console prints the last evaluation, so the would be 3.