World: r3wp

foreach [key val] b1 [print val]

That is just what I wanted, thanks Brian. Is this a recognised way 
to deal with data that is presented in a different order to the output 
requirement?

No, it's just a way to treat a block as fixed records, this time 
of two values each.

If you want variable records you either put the data in an inner 
block (as you have), or use a distinct datatype for the keys ans 
search for values of that datatype to find the next key.

I think I need to learn more before I can use this to the effect 
I need.   I was expecting your construct to all me to do this:
foreach [key val] b1 [print b1/:val/1]

I don't get what you want to do. Perhaps some sample data and the 
desired output?

probe b1
[random3 ["data4"] random1 ["data2"]]
probe b1/random1/1
data2


but as I dont know what random1 is I want to enumerate the values 
from the data structure.

Are you trying to get a specific data* or to enumerate all of random*?

Ah I think I am being a numpty. your structure already returns the 
data, but I need to be able to print the keys with the associated 
data.

foreach [r d] b1 [print [r d]]

You can do some formatting in the print statement, but it is that 
easy.

I will have different numbers of data elements in different keys, 
so I also need to keep track of which data is stored where, perhaps 
I need an array as the data element.

Your data already has an array as the data element, except we call 
them blocks.

b1: [random3 ["data1" "data2"] random1 ["data3"]]

foreach [r d] b1 [print [r mold d]]

I need to know what type of data I have put in data3.  It might be 
the same type as in data1 or data2, or something different again. 
 any one of maybe 10 types.   The actual data will be IP addresses 
& interface details & remote connection information.

You can specify ip addresses directly, as data of the tuple! type. 
Or you could have the data be doubles of strings and type flags.

Or if you would have at most one of each type, you could name the 
potential fields and have the data be name value pairs.

*a block of* name value pairs.

most of my different types will be strings I am expecting. 

Sometimes there will be up to about 4 of the same type (addresses 
& secondary addresses mostly)

[key [flags ["flag1" "flag2"] ips ["127.0.0.1" "192.168.1.1"]]

Sorry, missing a last ]

The pairs idea sounds productive, so it is a highly structured array 
with named groups?

Or you could go positional for the different types of data, instead 
of including the flags and ips words all of the time.
dat: [key [["flag1" "flag2"] ["127.0.0.1" "192.168.1.1"]]]
foreach [key val] dat [set [flags ips] val  ...]

Structured data makes things easier.

Thank you very much for you time & help.  I will need a while to 
digest this & make it work with my existing code.

I think this type of structure is going to be the core of most of 
the data extraction I need to do, so I must get to understand it 
very well. I have a section that uses an array, but some of the more 
interesting data manipulation needs to cope with more varied keys. 
Thanks.

This a pretty standard way for REBOL to do lightweight data structures. 
Blocks are lighter-weight than objects. Enjoy :)

.

Hi, is there an easy way to make this sort of structure work please?

data: [bike [wheels [2] owner [john]] pig [legs [4] owner [roger]]]

foreach [thing content] data [print [data/:thing/owner "~" data/:thing/wheels 
"~" data/:thing/legs]]

I want the invalid references (e.g. data/bike/legs) to return nothing 
so the list is printed for both things

I know I could put "" values in when I create the structure, but 
I wondered if the was a neater way to do this.

if you wrap a path in ATTEMPT, it will return none.

when it doesn't exist

Thanks Henrik. That sounds like what I need.

I like to do things like:

any [attempt [this/leads/nowhere] "Unknown"]

The task I am trying to accomadate is to output my data as a table. 
so I think I can adapt your example to return "" Thanks.

I cant work out how to turn that into a function, because if I do
att: func [paf][any [attempt [paf] ""]]
att this/leads/nowhere 

the invalid path returns an error before it can be passed to the 
function.   I bet there is a good answer. I have been looking at 
using :paf, but that makes it return the invalid path

lit-path!, it's done for that.

so I try to find a way to pass it as that sort of data type?

Not getting anywhere with this I am afraid.  where do I put the lit-path! 
please?

I have been trying this sort of thing
att: func [paf[lit-path!]][any [attempt [paf] ""]]
but I suspect that is not what Steeve means.

You suspect well, but you suspect too much.

It would be better if you knew all the data types in Rebol and their 
usages.

Currently you're only trying to "guess"  how to programm with Rebol, 
not to learn it.


I don't think it's always a good method to "give" the answer directly, 
especially when they are obvious.
It' gives some bad habits to the newcommers.
Sorry.

Steeve is an advocate of the Socratic method

BTW, I think   any [ attempt [paf] "" ] should be any [ attempt [.. 
] copy "" ] ... ie. you need a 'copy in there.

ok, I will continue to read the documentation. I think you are right 
Steeve, but it is hard to learn with no current programing skills. 
Perhaps I am just trying to find out how to solve my problems. 

Some of the data types seem quite straight forward, but some seem 
to need to be used before I can appreciate what they are exactly.. 
I try not to ask questions that are too trivial, and never before 
I have tried to research an answer for myself.  You maybe just misunderstand 
how stupid I am. ;-)

There are several good books on REBOL, even one in english

Do you think the web resources are in some way worse than the printed 
books Graham?

Mhinson, i think we all enjoy to answer to people like you.
Especially because you're a nice and psersistent personn.


But after some weeks, there are questions, we don't want to see comming 
from you.anymmore ;-)

Books are good because someone here gets to sell your their copy 
:)

If anyone has any good Rebol books in English that they would like 
to sell in the UK please let me know.  Thanks.

Steeve, I suspect you doubt the time & effort I have been putting 
into learning Rebol. If you have a clear idea about which sorts of 
questions I really should be able to answer from my own research 
it would give me some useful direction to my study I think. It is 
frustrating thatl I am often trying to guess how to create the structures 
I want, perhaps if I had a better foundation I would know know better 
how to learn more directly.