Context misery

... snickering out loud! --Scott Jones

Thanks for TFM ref. I'd completely failed to R that part. Sounds like we've both learnt from experience here.

Well, the moment, has passed. I coded what I wanted in another way--the code involved builds a data update layout dynamically from a CSV file: first row is the field names, subsequent rows the data, and it was generating global variables from the field names. It seems like a good idea at the time. Thanks again, --Colin.

aa is [1 2 3] bb is "myblock: copy aa" ** Script Error: aa has no value ** Where: myfunc ** Near: myblock: copy aa

All I'm trying to do is create a variable dunamically based on a name passed to a function. Thanks! Colin.

The REBOL/Core Users' Guide says (page 3-11): Unless it is necessary, evaluating strings is generally not a good practice. Evaluating strings is less efficient than evaluating blocks, and the context of words in a string is not known. I strongly recommend taking that advice to heart! Trying to construct source code strings that DO what you want is tricky at best, and a potential source of highly subtle bugs at worst. That said, when you define BB using the expression bb: join BlockName ": copy aa" and then DO that string, REBOL has no idea that you intend for the two-letter token "aa" in the string to indicate the LOCAL word AA in the current function. (Without going into deep and opaque waters, just remember that there can be *many* words whose names are spelled the same!) To get the value that's in your local variable to be the value stored in the (possibly!) new variable named by the BLOCKNAME parameter, you will need to force evaluation of your local AA and then use that result to construct the string. One possible (and possibly clumsy) way to do this is:

[ aa: copy [1 2 3] [ bb: rejoin [BlockName ": copy " mold aa] [ print ["aa is " mold aa] [ print ["bb is " mold bb] [ do bb [ ]

aa is [1 2 3] bb is "myblock: copy [1 2 3]" == [1 2 3]

== [1 2 3]

But *please* remember the old joke: "Doc, it hurts when I do this!" "Well, then don't do that!" ;-)

Why? If you can describe what you're trying to accomplish here, perhaps some of the old hands can offer some alternatives that won't be so tricky to deal with. For example... You can think of REBOL contexts as being like mini-dictionaries that map strings (the word names) to other values. (Now you see why different contexts can have words with the same name!) If you're trying to keep up with some data and you *really* need to associate values with names you can't know in advance, you could build your own "dictionary" as follows: fw: make object! [ storage: copy [] learn: func [ token [string!] value [any-type!] /local where ][ either none? find storage token [ append storage reduce [token value] ][ change/only storage value ] ] fetch: func [token [string!]] [ select storage token ] ]

== ["myblock" [1 2 3]]

== ["myblock" [1 2 3] "yourblock" [4 5 6]]

== ["myblock" [1 2 3] "yourblock" [4 5 6] "anyblock" [9 8 7]]

== [1 2 3] This is just a Q&D sample; an obvious improvement is to have LEARN return the VALUE argument as its result to facilitate embedding in larger expressions. Implementing that, and any other improvements, is left as an exercise to the reader! ;-) Hope this helps! -jn- ------------------------------------------------------------ Programming languages: compact, powerful, simple ... Pick any two! joel'dot'neely'at'fedex'dot'com

Well, it's dynamic insofar as I don't know what it is when the program starts. It is read as a string from a file. So (the original intention was) it goes into the function as a string, and comes out as a global variable. So I can use your function like this: myfunc to word! FieldName where Fieldname is the string. And that solves the original problem. Thanks! While I've got your attention, can I just say that I really really like this language! Thank you all for creating it.....I think my main problem is trying to run before I can walk, and often running straight into brick walls before donning the right head gear. --Colin.