World: r3wp

actually it will raise an error since time within the context of 
the object, is not yet set.

hm, isn't:

my-object: make object! [
  name: "me"
  time: now
]

equivalent?

ah, i see.

yes... obviously, but sometimes, the value you want to set within 
your object is already used within the code that is populating it... 
it was just an example  :-)

yeah, i see the difference. but i think the behaviour is a bit weird

why?

i would expect that time is identical to now after

time: now

but it's not.

forget it.

time: now
my-object: make object! [
  name: "me"
  mtime: time
]

behaves the same ...

time: time was the problem

yes exactly.  that's what the compose allows.

obviously one can say well, just use other words... but... its not 
always pretty... actually it rarely is.

one last question:

a: [ "a" "b" ]
how to write/append %to.txt a
so that
a b <- with whitespace inbetween 
gets written?

btw, Ladislav has another more flexible function similar to compose... 
 its called 'BUILD   ( http://www.fm.vslib.cz/~ladislav/rebol/)

write/append %to.txt form a

woot! thx

glad I can help  :-)

should have read strings, not blocks in the reference ....

Thanx for you help Maxim. Have to drive home now ...

Dirk, check out  compose/ONLY, eg:
>> blk: [1 2 3] compose/only [hello (blk)]
== [hello [1 2 3]]

I want to speed up access to a block of objects (unassociated) for 
a search algorithm.
Should I use LIST! or HASH! ?

It's a growing list of visited objects, and I'm searching it each 
time to see if the currently visited object has already been visited.

It looks like I should use HASH!, as it is designed to make lookup 
faster.
LIST! is designed for faster modifications.

I wonder what the conversion time is between BLOCK!, LIST! and HASH! 
there must be some kind of penalty there.

perhaps the objects could just contain a  visited field

No, I'm searching the system object; I can't modify the objects.

ah

what are you keying off  of?

Search term is a word, but I want to support strings as well.

If lookup speed is primary, use hash!, if you're doing a lot of inserts 
and removes, use list! There is overhead to has items for lookup, 
but the speedup is enormous on lookups..

also remmember that lists are at their tails after inserts and append... 
this is usefull, but quite frustrating to discover when you don't 
know about it.

A quick test looks like using a hash didn't help in my case, the 
major work must be somewhere else.

Yes, I am aware of the index position confusion with list!.

Is it possible to turn off: ** Math Error: Math or number overflow 
?

My gcc compiler here warn me of integer overflow, but I can run the 
C program, and bits are lost. But that can be ok in some cases, for 
example to calculate noise. I'm wondering, if I can do that in a 
fast way with REBOL. Example:
46341 * 46341

will produce an integer overflow. I just want the result with the 
high order bits lost.

Good question. I would like to avoid this error as well. A overflow 
would be OK in most cases.

Youd could bypass it with something like:
(1. * 46341 * 46341) // (2 ** 31)

How do you do this when you have a lot of claculation that use user 
input?

The user could input very large numbers.

Not sure -- and of course it probably doesn't meet Geomol's request 
for a "fast way"

>> 46341 * 46341
** Math Error: Math or number overflow
** Near: 46341 * 46341
>> 46341x1 * 46341x1
== -2147479015x1

("hidden feature" of pairs, used by nenad in is mysql protocol handler 
:)

LOL Wow! That's nice, Gabriele!

Also a fine solution, Sunanda! That might be one of the fastest way 
to do it. Maybe I'll just use RANDOM in my noise generating routine, 
but if that's not good enough, I'll probably use one of these suggestions.

Cool. This trick could be used to implement intervall arithmetic. 
Using a PAIR to store the upper/lower bound of ranges. Than we only 
need special operator implementations for * / to handle all cases.

I was trying to implement this function in REBOL:

function IntNoise(32-bit integer: x)
 

    x = (x<<13) ^ x;

     return ( 1.0 - ( (x * (x * x * 15731 + 789221) + 1376312589) & 7fffffff) 
     / 1073741824.0);
end IntNoise function


Using pair didn't do the job, I guess because of truncating along 
the way. Sunanda's method works.

Question: I have a block that represents several records (fixed size 
number of fields). Now I need to extend each record by one column. 
Inserting a new entry every X entries in the block. IIRC there is 
a special function to deal with fixed size blocks for such thing. 
Like remove-each but more generic.

the simplest way I come up is:
	FORSKIP series record-size [
		APPEND result COPY/PART series
		APPEND result new-value
	]


But this copies the series. Is there a nice inplace extension solution?

parse series[any[ record-size skip p: (p: insert  p new-value) :p 
]]
but that  shifts  a lot.
would use
 insert clear series  result

and for speed there is insert/part to avoid all the small temp blocks.

something inbuild not.

I have a DELIMIT function that will do it, changing the series in 
place, with the exception of the trailing element. So the final result 
would look like this:

	append delimit/skip series new-value record-size new-value

The basic idea you want is this:

	series: skip series size 
	series: head forskip series size + 1 [insert/only series value]


My DELIMIT func also works with list! and any-string! types correctly, 
which simple code above doesn't account for (the +1 part is simplified).

To move a file, one solution is:
write/binary <destination> read/binary <origin>
delete <origin>

If you leave out the delete, you've got a copying file routine.

To copy large files, Carl gave some ideas in this blog:
http://www.rebol.net/article/0281.html

Cool thanks

If you just need to move a file within the same hard drive, there 
may be some tricks with renaming or calling external commands that 
will likely be faster. Be sure to check those out too.