World: r3wp

b: ["s1" "s2" "s3" "s1"]
parse b[any[to "s1" p: (p/1: copy "t0") skip]]
? b

Q2 again: Sorry, my axplanaition was a little unclear: 

I have a row from a database, and store away one block, and display 
the other for the user. The user may, or may not, change the data.
>> orig: ["Mr" "Petr" "Ustinov"]
>> data: ["Sir" "Peter" "Ustinov"]
>> magic-changed-func orig data
== [1 2]

orig: ["Mr" "Petr" "Ustinov"]
data: ["Sir" "Peter" "Ustinov"]
; same length !
out: copy[]
repeat i length? orig [ 
	if orig/:i <> data/:i [
		append out i
	]
] 
? out

Q1:use [x] [

Sorry

Q1:
use [x] [
    x: block
    while [x: find x none!] [change x copy ""]
]

Ingo, I have similar feelings too sometimes. I need a higher level 
function to do some things like that, but it's not there....

I often wanted reduce and compose to not make a copy for you, but 
work directly on the block. (Perhaps new functions "induce" and "impose" 
?)

induce should be fairly easy -- walk the block with 'for and 'poke 
back the value

blk: [a b c] 
format: [(1 + 2) (random 100) c]

impose: func [blk format][repeat n length? format [if paren? format/:n 
[poke blk n do format/:n]]]
impose blk format
;blk == [3 95 c]

For induce I think I would use do/next.

induce: func [blk format][change blk reduce format]  ; (except, as 
a native!, without creating a temporary block)
induce blk [1 + 2 random 100 'c]
; == [3 67 c]

Hi Voker, BrianH, thanks for your ideas ... they look mighty long 
compared to normal Rebol code ;-)

Sorry, I wanted to type Volker, of course!

; Q1: copy/deep will give you new strings:
block: [none none none]
new-block: copy/deep replace/all block 'none {}

; Q1 Or if you know you can reduce it you could do something obtuse 
like:
block: ["a" none "b" none none]
use [none][none: does [copy {}] bind block 'none]
reduce block

But if you do need to do an actual replace on the original block 
- see the other solutions :-)

Hi Brett, your first version looks pretty good ... now I'll have 
to dig out my little profiler, and see what's the fastest of all 
of these ;-)

I reckon the parse will win.

Brett's is the nicest looking though.

Brett, your obtuse way will only work if you are replacing 'none 
(as a word), but not none! values.

eg. reduce your input block:
	block: reduce ["a" none "b" none none]

Agreed Anton and perhaps that shows the obtuse method is not a great 
idea for this situation  - though perhaps an interesting one ;-)

In case anyone is interested... http://www.rebol.org/cgi-bin/cgiwrap/rebol/view-script.r?script=reboldiff.r

Are there any other instances where the a: copy [] vs. a: [] "problem" 
appears?

I'm have a bug where two arrays:

1. an array with data that can be manipulated

2. a similar one containing default data, which is used whenever 
I want to reset the first one


They apparently "stick" together with synchronized values. When I 
manipulate array 1, array 2 changes too. This would be the old COPY 
problem, but I use COPY everywhere, whenever I need to create array 
2.


However I do frequently PICK values from array 2 and POKE it in array 
1 at the same location to reset a specific location to a default 
value. Would that create a similar problem?

it depends on the kind of value you are picking/poking.

i guess you need copy/deep and poke ... copy pick ...

I pick and poke arrays

i mean, what is the result of PICK? i.e. what is inside the arrays?

if the arrays have multiple dimensions, you need copy/deep. And if 
there are objects inside, those objects are not copied, then you 
need explicit work (copying all objects in a loop using 'make)

Volker, the arrays are indeed both 2 dimensional and contain objects. 
I'll try a different init method.

gabriele, the arrays contain other arrays, hence PICK returns arrays 
of objects.

so, copy/deep, and, as volker suggests, you're likely to need to 
clone the objects too.

thanks, both. problem solved. :-)

a one liner I didn't see on rebol.com: Sum of all numbers in a block!:

do do replace/all mold [1 2 3 4 5] " " " + "

Clever!
But crucially dependent on the block being contained on one line:
 xx: {
 do do replace/all mold [1 2 3
  4 5] " " " + "
 }
 do xx

But then you did call it a one-liner :-)

do trim/lines xx could fix that

Is there a function which cuts the suffix, so i can go from %file.txt 
to %file.html ? I  remember darkly there is one now.

I think there is one which splits a file up in an object with path, 
filename and extension. can't remember which though....

thats decode-url, good thought, but not in my case.

what about cutting at last occurance of "dot"?

longer :) but thats what i do now.

>> prefix: func [filename][copy/part file find/last file "."]
>> prefix file
== %movie.cd1.divx-rel6

where - >> file: %movie.cd1.divx-rel6.avi

maybe 'prefix? would be good addition to Core, as we have 'suffix? 
already? :-)

thats cool, better than mine :) thanks.

but prefix is wrong :-) body uses my global 'file variable - should 
be prefix: func [filename][copy/part filename find/last filename 
"."]

maybe some solution based upon short parse rule could be produced 
too :-)

i guess parse-rule would be longer in this case. now trying

re-suffix: func [file suffix][append copy/part file find/last file 
"." suffix]

cute!