World: r3wp

I get the feeling that I'm going to want to have an analysis tool 
which will read through the functions, find any variable: assignments, 
and ensure they're in the local list unless there's some sort of 
indication they should be global.  Because it seems relatively uncommon 
that I would, inside a function, set things in the global space. 
 I'd be happy to use something wordier (set?) for that

I recommend FUNC over FUNCTION because having "/local" written makes 
it clearer and explicit what the locals are, and is shorter when 
there are no locals. Compare:

When there are no locals, func wins, because less characters to type.
	func []
	function [][]

When there are locals, same number of characters written, but func 
more clearly specifies the locals.
	func [/local]
	function [][]

Additionally, when you are modifying your func spec back and forth 
so that there is a need, or no longer a need, for locals, then func 
wins by less typing needed.

Hm, well, it's not a tremendous deal but I feel like always being 
forced to remember typing in that second group would remind me that 
I need to think about what goes in it

Is there a way to set things locally in a do block?

Or do you have to do a nameless function to get a local context?

e.g. do func[/local v] [v: 1+2]

I go without such a tool for analysing function local variable consistency, 
which, I think, turns out to be a difficult problem to solve. Some 
people have written alternative function creators which somehow make 
set-words into locals by default (Ladislav ? with his lfunc ?) or 
something like that. I just maintain a strict habit of checking for 
accidental globals. It's good to review your use of variables regularly 
anyway, and be aware of what context they're bound to.

use [v][v: 1 + 2]

Ah, an lfunc, that sounds nice

do [
	use [v][v: 1 + 2]
]

context [
	v: 1 + 2
	print v
]

same as
make object! [
	v: 1 + 2
	print v
]

I see... context looks like a good thing, great!

Yes, very useful.

?? context

When I do something like a for loop and I specify a name for the 
loop variable, is that defined globally by default or locally?

which reminds me; make-enum-type can be optimized like so:

make-enum-type: func [ possibilities [block!] ] [
	make enum! [
		p: to-hash possibilities
		l: length? possibilities
	]
]

so no need for a local at all.

Loop functions set words local, in a temporary context. You can test 
whether loop functions set words global or not quite easily:

>> for i 1 10 1 []
>> i
** Script Error: i has no value
** Near: iÂ

Yes, thanks for reminding me of the at-hand-interpret-as-you-type 
thing :)

All I can say is, enjoy...

Is there a way to get the native-switch that is better than how I've 
done it?

(But I was thinking, the above doesn't prove that  i  is not set 
global during the loop, then unset at the end, but you wouldn't expect 
that sort of sneaky behaviour...:)

Yes, you've set 'native-switch global. It appears to be used only 
in the enum/switch function.

You could simply refer to system/words/switch instead. No extra variable 
necessary here.

A-ha... nice.  Now here's something... can I make it so that my test-block 
runs the code in its body in a local context?

I guess, use [][do :block] ?

No, that use would be no different than just
	do :block

Because, by not specifying any use locals, you are making a context 
without any local words in it.

(ah... except 'self, but that's not important here)

Better than
	loop times [do :block]
is
	loop times block

Now that one I got from a sample on the web.  :)  http://www.rebol.org/cgi-bin/cgiwrap/rebol/view-script.r?script=timeblk.r

Which also didn't declare start: locally...

The words in block maintain their bindings. This is what you want; 
the words retain the meanings from the context the user wrote them 
in. (ie. your locals do not affect those words because nowhere do 
you bind the words to any of your own contexts.)

do context[do :block] ... that would give it a new context and run 
it there.  What kind of thing would that break?

So if I write
	test-block "section" [ print reps ]


then REPS means what *I* (the user of the test-block function) thinks 
it means, not what test-block thinks in its little context.

Hmmm.  Ok, so if I want to have local variables in a test-block the 
context declaration would need to live there?  That is different?

(First DO does nothing extra, just returns the object)
Again, 
	context [do :block]
is no more (except 'self) than:
	do :block

I did try that but it didn't seem to evaluate the block

You could do something like this:
	use [var1 var2] block
or
	context join [var1: 100 var2: 200] block

Now it's evaluating, hm.  Wonder what I did before.

There're lots of confusions here when starting out :) beware !

Yes!

But I'm wondering why you want to subvert the meaning of the words 
in the block to your local meanings.

Well, I have one test block after another in a line

Surely you want the block to retain all its meanings ?

I'm used to C++, so I like scopes.  They make me happy :)

So I was wondering if I could let the concept of each test-block 
being a scope come from test-block itself

Rebol's contexts are better ! (But scope is good for compiling.)