What deserves to be a datatype?

[bradrn]

Starting in the middle:

@hostilefork

One place I see THE-BLOCK! coming into great use is if for a dialect that is not purely mechanical (the way PICK and FOR-EACH are), and leaving the @ off of a block signaling that you would like the "INSIDE / IN" binding to be applied automatically.

This is simply going back to what I said originally: ‘The closest to an explanation I’ve found is that these types are useful in dialecting’.

But then, if you’re willing to accept that as sufficient reason for syntax to exist… well, you can use that to justify basically any syntax, as indeed I once tried to do:

@bradrn

I do see this as having real utility in dialects. For instance, a dialect to interface with C++ code might use this to refer to ::global variables. Or a statistical modelling library might want to follow precedent when talking about regression ~parameters. Or filesystem operations on Windows might want to refer to \\REMOTE directories… anyway, you get my point, hopefully.

The lesson I took out of that discussion is that adding syntax purely for usage in dialected code is a bad idea, because it’s impossible to know where to stop.

That being said, beyond dialecting, it is pretty useful to have this distinction of ‘this list represents code, evaluate please’ vs ‘this list is just a list, do not evaluate’. After all, it’s nice to be able to pass around lists without worrying that they’ll be evaluated randomly. And it makes sense to store that distinction on the datatype, rather than as a refinement (cf. /ONLY vs antiforms). So, on balance… yeah, I think THE-* is starting to make much more sense to me now.

@hostilefork

And I will reiterate that an important application of TYPE-TUPLE! is when you have a predicate function inside an object or module

Ah-ha, I keep on forgetting that Rebol uses TUPLE!s for access within an object. (In my defense, historical Rebol didn’t use dot-syntax, and neither do some of the languages I use daily, so I sometimes forget it exists.)

Although… then again, this looks like it’s yet another instance of ‘syntax which is only useful in dialects’. That still bothers me, for the reasons I already mentioned.

@hostilefork

Imagine I decide to use $1 and $2 etc. to be some kind of positional substitution notation in a dialect

OK, I didn’t even think of that possibility. That makes sense.

I disagree with it though, for two reasons:

• I think MONEY! is actually very useful. Working with money requires specialised requirements (e.g. fixed-point storage), which can be a bit painful — so having that type built-in to the language eliminates a whole class of subtle errors. And, of course, all kinds of software requires working with money.
• I think positional substitution is a particularly annoying kind of substitution. I use it in Bash, and hate it. I’d much rather do something like substitute [a b $bar c d $foo e f] {foo: <some> bar: <thing>}, which is less error-prone and more descriptive.

So, I’d rank them the other way around: MONEY! is most useful, and DOLLAR-INTEGER! is less useful.

@hostilefork

I would use DOLLAR-INTEGER! more than MONEY! in the kinds of things I'd use Rebol stuff for.

Admittedly, I would do the same. But for a general-purpose language I think MONEY! is important and very useful.

@hostilefork

Where do you find the time for all these interests?

I couldn’t really tell you; I’ve always just had very broad interests. And linguistics has always been one of my favourite areas.