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World: r3wp

[Core] Discuss core issues

Anton
20-Jun-2008
[10687]
It's kind of like an "apply-any".
Henrik
21-Jun-2008
[10688]
simple problem:

>> a: [1 2 3 4 5]
== [1 2 3 4 5]
>> b: at a 3
== [3 4 5]
>> a
== [1 2 3 4 5]
>> b
== [3 4 5]
>> remove a
== [2 3 4 5]
>> b

== [4 5] ; I wonder if it's possible to make the index "sticky" at 
[3 4 5] in a relatively simple way. If it were, that would be very 
cool.
Graham
21-Jun-2008
[10689]
copy it first!  :)
Henrik
21-Jun-2008
[10690]
nope, it has to be the same series
Graham
21-Jun-2008
[10691]
and if you copy the index? as well?
Henrik
21-Jun-2008
[10692]
it must be the same series
Chris
21-Jun-2008
[10693]
Unless this is a feature request, you'll need an alternative to remove...
Henrik
21-Jun-2008
[10694]
half a feature request and half trying to find a quick way to solve 
it. seems there is not an easy way.
[unknown: 5]
21-Jun-2008
[10695]
can you just get around the problem by setting a: next a   ?
Henrik
21-Jun-2008
[10696]
yes. that's janitoring of the index, which could be prone to bugs, 
etc.
[unknown: 5]
21-Jun-2008
[10697]
yeah you'll definately have to be more judicial with your code but 
I'm thinking that the mechanics of it is the way it is intended to 
operate.
Henrik
21-Jun-2008
[10698x2]
yes, it is. it would be too hard to track from inside rebol when 
an index should move.
(but if it were possible, some code would be greatly simplified)
Dockimbel
21-Jun-2008
[10700]
>> a: make list! [1 2 3 4 5]
== make list! [1 2 3 4 5]
>> b: at a 3
== make list! [3 4 5]
>> a
== make list! [1 2 3 4 5]
>> b
== make list! [3 4 5]
>> remove a
== make list! [2 3 4 5]
>> b
== make list! [3 4 5]
[unknown: 5]
21-Jun-2008
[10701x6]
Let's talk memory...
I that in the following the 10 represents 10 "bytes"?  a: make string! 
10
So how to we define those things in a block?
I know we can initilize the block with for example:

a: make block! 10 

But how do we determine what is in the block comprises a byte?
I know that in a string each character represents a byte but even 
then how much overhead is allocated merely by a: make string! 0?
These are the kinda things I wish Carl would go over so we can best 
optimize our use of memory.
Henrik
22-Jun-2008
[10707]
interesting, dockimbel. thanks.
PeterWood
22-Jun-2008
[10708]
There is a lot of information about Rebol's memory usage in the mailing 
list archive. You culd start here: http://www.rebol.org/cgi-bin/cgiwrap/rebol/ml-topic-index.r?i=memory
[unknown: 5]
23-Jun-2008
[10709x4]
I have reassociated my scripts in windows with the new 2.7.6 core 
but I now get an error whenever I attempt to open them which is:

** Access Error: Cannot open /C/Documents
** Near: do/args script system/script/args

Any ideas?
It appears to see a broken path and sees the rest of the path as 
an argument.  Not sure where it is checking yet to get this information.
Fixed it.
I went into the registry and found the reference to rebview and deleted 
its registry keys and reassociated the .r extension with the rebol/view 
2.7.6 product.
Chris
28-Jun-2008
[10713x2]
; request for comments --

assert-all: func [cases [block!] /local value][
	until [
		set [value cases] do/next cases
		unless value cases/1
		cases: next cases
		any [not value tail? cases]
	]
	value
]
Usage:

	assert-all [
		a < 10 [print "a is more than 10"]
		a > 0 [print "a is less than 0"]
	]


It's the opposite of 'case really.  If any of the cases are false, 
the related block is evaluated and the function returns none/false. 
 If all cases are true, it returns the value of the last successful 
case.
[unknown: 5]
28-Jun-2008
[10715]
Why would we need that as opposed to just changing the current evaluation 
of existing case?
Henrik
28-Jun-2008
[10716x2]
I would like to see a good implementation of a function that performs 
a sequence of code blocks. If a code block is good, the next one 
is run. If the code block causes an error, a secondary code block 
that is either generic for all code blocks or specific to that particular 
code block is run. I'm thinking step-by-step code that either runs 
successfully or causes a generic or specific error.


I don't know if it makes sense to do that, but I sometimes miss that 
if I need to do something with user friendly network connectivity.
although I've recently switched to state machines for that kind of 
code.
Graham
28-Jun-2008
[10718]
all-nots ?
Chris
28-Jun-2008
[10719x2]
Paul: it's a common enough pattern, I'd like to find the most appropriate 
way to express it.  Actually, that's the principle behind QM (which 
of course, this is intended for).  The alternative case above would 
be:

	case [
		not a < 10 [print "a is more than 10"]
		not result: a > 0 [print "a is less than 0"]
	]
	result


Requires a 'not statement for each test, requires an extra word to 
track the result and does not return a meaningful value.  Consider 
this:

	if assert-all [

  user/has-role? 'editor [make error! "You do not have required permission"]
		article: get-param 'article [redirect-to %/articles/create]
		10'000 < length? article [make error! "Article is too long"]
	][
		save %article.txt article
		redirect-to %/articles/list
	]
Henrik, how does your scenario differ?  Do you have a sample of your 
solution at work?
Henrik
28-Jun-2008
[10721]
I had a function that does this a while ago, but I have to dig it 
up
Chris
28-Jun-2008
[10722x3]
Graham, I'm still pondering naming.  'assert seems to evoke unit 
tests, that's not what this is.  'all-nots doesn't quite get the 
essence either.  'all-else is a possibility?  Until then, I still 
lean toward 'assert-all.
H: is this the type of problem you were addressing?
That is, I have a series of tests, each requiring a case for failure...
Henrik
28-Jun-2008
[10725]
Chris, I guess it could work.
Chris
28-Jun-2008
[10726]
I'm curious re. approach, expression and naming...
Henrik
28-Jun-2008
[10727x2]
found it, but I remember it being more elegant than the code I found 
here...
sorry, it does not work very well. I think I would build a new one 
from scratch if I needed it again.
Chris
28-Jun-2008
[10729]
I get that -- a sign of personal progress, perhaps?
Henrik
28-Jun-2008
[10730]
well, I tried a single line of code with it, and it didn't do what 
I wanted. I guess I could ask myself if I would write that kind of 
code today. :-)
[unknown: 5]
28-Jun-2008
[10731]
Chris - 'case is native so even adding a 'not statement is going 
to be faster solution I think.
Graham
28-Jun-2008
[10732x2]
Should one go for speed or readability?
If it's a time critical app like a web server I'd go for speed ...
Chris
28-Jun-2008
[10734x3]
Readability.  I want it to be fast, of course, but long-term it's 
not worth the compromise.  I want to do more with less.
Indeed 'all would be fastest yet, except you don't get feedback at 
the point of failure.
You could use 'foreach which'd be fast, but then you'd have to block! 
your case as well as your fallback losing readability.