World: r3wp

to path -> to pass ..

It's pretty easy to figure out when you realize that second on an 
action! returns an integer. Everything else follows from there.

At this point, I can't imagine what the path action! would be good 
for. Perhaps it is part of the object! internals?

Volker, by protocol do you mean a port type?

Cant have a use, else i had heard of it :) Practical use: it blocks 
mold. Recursive data, Code-obfuscation?
!> a: context[b: 1 c: 2]  path a 'b  ?? a
a: make object! [
    b: end
    c: 2
]

Yes.

Would be able to implement find on a port that way.

I'm going to copy my path question to RT Q&A.

let us know the answer! paste it here if u got any!

path is internal, and should probably not be exposed. my guess is 
that it has to do with path evaluation.

You are probably right that it wasn't intended to be exposed, but 
you got my curiosity going. What is it used for internally?

I mean, it says "Path selection." right in the doc comment so that's 
a good guess :) But how does it help with path selection? How is 
it used? Just for implementing set-path assignment?

For that matter, what types implement the path action?

i don't have answers. when i noticed it months ago and asked carl, 
he said it was an internal thing. no more details.

I had a problem with SWITCH, and it turned out to be a funny thing 
with SELECT (see source switch). If you've got a block like this:
blk: [1 word "string" 1.2 01:00:00 1-11-2005 any-type! 4]
you can do things like this:
>> select blk 1
== word
>> select blk 1.2
== 1:00
>> select blk 'word
== "string"
>> select blk 1:00
== 1-Nov-2005
>> select blk 1-11-2005
== any-type!

And now the fun (or strange) part:
>> select blk any-type!
== word

It's possible to select on a datatype. The first element in the block 
(1) is of type any-type!, so I get: word. It's possible to do things 
like:
>> select blk date!
== any-type!
>> select blk time!
== 1-Nov-2005

So how do I select a datatype in a block? I could do this:
>> select blk to-word any-type!
== 4
or something like this:
>> select reduce [file! 1 url! 2] url!
== 2
I can cope with this in my code, just found it peculiar.

In the last part, what I'm trying to do, is selecting a datatype 
word in a block.

It all came from the include function in Canvas. I wanted it to be 
able to include modules both from diskfiles and URLs. So I did something 
like:
switch type? object [
	file!	[...]
	url!	[...]
]
But this wont work, and I ended up doing:
switch to-word type? object [


Maybe there should be some notes about this behaviour of SELECT in 
the wikibook?

see switch type?/word ...

Brilliant! Of course Carl've thought about that. :-)

Yeah, this one catch me too some times ago ;-)

Searching for datatype works with FIND as well. It's very handy

I wonder if it would be possible to implement a dialect to get at 
parts of a series as in python.  With rebcode?


instead of copy/part string 4 ... , string/[:4], or if I want the 
5 and 6 elements, then string/[5,6]

Very posible

that seems easier than copy/part skip string 4 2

I believe Greg already has something like that he named his function 
slice.

But now we can use rebcode to speed it up ?

Is Gregg's function dialected ?

Lost me there.

This type of function is quite fast in native rebol.

it's just a pain to write.

the power of a language can be measured by how few symbols are required 
to perform a given task.

I don't think so. It all depends on the functionality you want.

Well you can create your on slice function.

don't want to :)

I want native handling that is expressive, and short

Graham, I don't think that's a very good measure. REBOL isn't Perl, 
you know, but that doesn't make it less powerful.

But also it assists in debugging programs.  It is well known that 
the number of errors per line is fairly constant.  You reduce the 
number of words you use with a powerful language, and this leads 
automatically to reduced number of errors since you need fewer lines.

substring: func [
    [catch]
    source [string!]
    spec [block!]
    /local start stop rule
][
    rule: [set start integer! '.. set stop integer!]
    unless parse spec rule [
        throw make error! "Invalid range spec."
    ]
    copy/part skip source start stop
]

You can create your own dialects and grammar. But don't ask for everything 
to be written to your liking.

substring "abcd" [2 .. 3]

; 1-based indexing
slice: func [str start len] [copy/part at str start len]
; 0-based indexing
slice: func [str start len] [copy/part skip str start len]

Fill in with doc strings and [catch] attributes, but the algorithm 
doesn't have to be hard.

which is briefer ?

substring "abcd" [ 2 .. 3 ]

and "abcd"/[2 .. 3]

The first one, because you can tell what it's doing without having 
to remember more syntax.

I'm not saying that Rebol should be Python, just that it could be 
useful this way.

How about:  slice "abcd" 2 3

The '.. in my small dialect block is pure syntax sugar and un-necessary 
but easy to remember for some people.

[2 .. 3] hints that it is a range.

yeah

so, "abcd"/[ 2 3 ]

You don't need a dialect processor and its overhead for what is essentially 
a library function.