World: r3wp

I guess, that I owe a little more to the readers, so here is an example 
illustrating what I actually mean:

let's define a block as follows:

    a-block: [[1] [2]]


at the present state, it is obvious, that first a-block and second 
a-block are not identical
illustration:

    same? first a-block second a-block ; == false

now, let's use the CHANGE function:

    change/only next a-block first a-block
    a-block ; == [[1] [1]]

due to the way we did it,

and due to reflexivity of identity, first a-block and second a-block 
yield the same value,
after this operation

("the same" in the sense, that there is only one value, which happens 
to be the value both expressions yield.)


since first a-block and second a-block are two expressions yielding 
just one value,
we conclude (as a consequence of that), that the respective value
is not contained in the first slot of the A-BLOCK block

(if it were "contained" in there we could not be able to see, that 
the value is actually not "contained" in there)


Usíng the same approach for any other REBOL value, we can demonstrate, 
that no value is "contained" in "value slot". Since we *can* find 
out "Which value is the first a-block value?" there is only one conclusion 
we can make: using the first a-block expression we can refer to the 
value (this is why I use the words "reference", "refer"), but that 
does not mean, any other "reference" cannot "refer" to that value 
as well, thus the value "is not contained", but just "referenced".

Another (less useful) way to look at it is to say that no value is 
really the same as or identical to any other value, only to itself 
(the same value slot). But since that's a useless way to look at 
it, we instead compare the bits of the different value slots and 
if they match we then say that they are the SAME? (or IDENTICAL?, 
depending on how many bits we are comparing). Expediency for the 
win!

Another (less useful) way to look at it is to say that no value is 
really the same as or identical to any other value...Expediency for 
the win!

 - yes, that is where the expediency is what should win, exactly as 
 you pointed out.

(We need to have the documentation mentioning Rebol values, compare 
results of different expressions to find out whether they are identical 
or not, document whether some value is modified by some function, 
...)

no value is really the same as or identical to any other value, only 
to itself (the same value slot).

- well, the first part of the sentence is a law of logic - nothing 
can be identical with any other thing except for itself - which is 
true, and I even used that law to define the identity

The problem is only with the second part of the sentence, "trying" 
to identify Rebol values as "value slots", which is not useful, and 
wrong.

And then you defined "value" to be something referred to by the value 
slot, not what was in the value slot, or the value slot itself. Without 
that definition, your definition of "identical" doesn't work. Which 
is why that was another way to look at it, the "other" in this case 
referring to way to look at what a value is and how to think of a 
value slot.

I'm not saying that any of these definitions are wrong, but yours 
is more useful.

I should probably explain, why I added the "and wrong" part. I did 
it, since not all Rebol values are representable using 128 bits or 
less. In that case we must have more than 128 bits no matter how 
fervently we wish something else

Yeah. The main difference between what you are saying and what I'm 
saying is for that what you are referring to by values that don't 
fit in 128 bits, the values that are in the value slots are what 
I've been calling "reference values". Thus the distinction between 
"immediate" types and "reference" types. This is a similar situation 
to (primarily OOP) languages that make a distinction between boxed 
and unboxed values, except for us even the "unboxed" values are in 
a box: the value slot. Making this distinction lets us reuse the 
large amount of existing reasoning that has been applied to OOP languages. 
This is particularly helpful when we are trying to solve the same 
problems that many other languages are, but the existing research 
on those problems is being done by people working in those other 
languages. Finding comparable distinctions makes it easier to implement 
comparable solutions :)

For instance, I'd hate to have to start from scratch in creating 
a concurrency model, especially when we can start from the Go model 
instead.

> except for us even the "unboxed" values are in a box: the value 
slot.


It's the extreme semantic overloading of "value", that is the problem 
here. :)

Isn't it always? It all depends on what you value i guess :)

Boxing is no good example in this case, as it describes something 
different.

But the terminology underlying the boxing process actually is useful, 
namely value types and reference types.

The immediate! typeset in R3 captures (or at least tries to) the 
former.

And we didn't make a typeset for the latter because not existing 
in the former is enough.

And Ladislav's "Identify" article is exceedingly useful in defining 
meaningful dimensions of the term "value" in REBOL's context.

Specifying a "REBOL value" as the sum of it's attributes, for example.

One attribute common to all REBOL values being type. Other attributes 
being type-dependent.

Yup. Works great until you try to use "value" in a sentence, because 
of English's ambiguity :(

Even the actual "payload data" of a REBOL value is a type-dependent 
attribute.

(unset! or none! values having no such "payload data", for example.)

And now of course the problem is, that we refer to different entities 
as "value", depending on context. Amongst those entities often referred 
to as "value" are:
- the "REBOL value", as defined above
- the "payload data" of a "REBOL value"
- the "value slot" implementation detail

Is there a way how to mold error into nice looking string?

I mean... I can do:
>> if error? err: try [1 / 0][probe err false]
make error! [
    code: 400
    type: 'Math
    id: 'zero-divide
    arg1: none
    arg2: none
    arg3: none
    near: [/ 0]
    where: [/ try]
]
== false


but what if I would like to form the error message to look like if 
the error is really evaluated:

>> do err
** Math error: attempt to divide by zero
** Where: / try
** Near: / 0

Can we have the error message formater available or is it hidden 
for some security or other reason?

I format them myself

how... do you have a list of all available error ids?

is there any idea how to place an break point int code for debugging 
reason, and release it (continue)?

int = into

Oldes - you can try to grab them out of here, but not sure how easy 
that will be:
   probe system/catalog/errors

thanks... that's what I was looking for.

Pavel... I usually use ASK with any value/message as a break point 
while debugging. Or just PROBE is I don't need to stop the evaluation.

Sunanda: not so easy, require some binding.

So far I have this:
my-attempt: funct[code /local val][
	either error? set/any 'val try code [
		val: to-object val 
		do bind [
			print rejoin [

    "!! " val/type  " error: " reduce system/catalog/errors/(val/type)/(val/id) 
    #"^/"
				"!! Where: " val/where #"^/"
				;"!! Near: " val/near  #"^/"
			]
		] val
		false
	][
		:val
	]
] 

my-attempt [debase #ff]
my-attempt [1 / 0]

but not perfect... the Near and Where info is modified :-/

How to convert issue! to binary! in R3? I was using debase in R2, 
but it's not working anymore (I guess because of unicode).

small observation:

>> any-word? #a
== true

that is possibly why it no longer works.

hm.. so debase/base next to-string  #ff 16

2 Oldes Great idea thanks

Oldes, wasn't there a function in R3 which allows you to get the 
string from an error...directly?

I was using this function in R2:
parse-error:  func[
    error [object!]
    /local type id arg1 arg2 arg3 where err-desc
][
    type: error/type
    id: error/id
    where: mold get/any in error 'where
    either any [
        unset? get/any in error 'arg1
        unset? get/any in error 'arg2
        unset? get/any in error 'arg3
    ][
        arg1: arg2: arg3: "(missing value)"
    ][
        arg1: error/arg1
        arg2: error/arg2
        arg3: error/arg3
    ]
    err-desc: system/error/:type
    rejoin [
        "** " err-desc/type ": "
        reduce either block? err-desc/:id [
            bind system/error/:type/:id 'arg1
        ][
            err-desc/:id
        ]
        newline
        "** Where: " where
        newline
        "** Near: " mold error/near
    ]
]

>> f: does [1 / 0]
>> if error? err: try [f][print parse-error disarm err]
** Math Error: Attempt to divide by zero
** Where: f
** Near: [1 / 0]

In R3 the WHERE and NEAR report is different

Plus, there is a long-term CC ticket about the off-by-one Near for 
operator-generated errors.

Yes.. I just wanted to write, that the NEAR is the main problem.

I just have this:

unless rebol3? [result: disarm :result]

unless silent [
	print "ERROR"
	prin "ID: "  probe result/id
	prin "In: "  probe result/arg1
	prin "Near: "  probe result/near
	if rebol3? [prin "Where: "  probe result/where]
]

With REBOL3? predefined

Seems I'm only missing the textual description

Oldes, a perhaps simpler version for R2 is: http://www.rebol.it/power-mezz/mezz/form-error.html

I thought FORM was supposed to be able to do the same thing on R3, 
not implemented yet?