World: r3wp

example for issue!
>> test-syn issue-char "#?"

it prints out all the errors

works with R2 or R3

but you need to have [disarm] when used with R3.
I use this defintion:
>> unless value? 'disarm [disarm: func[e][:e]]

issue-syntax-R3: [#"#" some issue-char-R3 termination]
issue-syntax-R2: [#"#" any issue-char-R2 termination]

tag-char-beg: complement union whitespace charset {=<>"^@}
tag-char: complement charset {">^@}


tag-syntax-R3: [#"<" [not #"]" tag-char-beg | quoted-string] any 
[some tag-char | quoted-string] #">" termination]

tag-syntax-R2: [#"<" [tag-char-beg | quoted-string] any [some tag-char 
| quoted-string] #">" termination]

in R3 the exception with the starting #]" may be a bug

Someone's complained about it, but I think it's sn intentional fix 
to this bug in R2:
>> [ < ]
== [<]
>> [<]
** Syntax Error: Invalid tag -- <
** Near: (line 1) [<]

It's more related with a wrong doing with the tag! decoding to me

but anyway

When people wanted to refer to the < word in R2, and they can't use 
the lit-word syntax for arrow words in R3 and pre-a97 R3, one way 
is to store that word in a block and use FIRST to get the value. 
However, in R2 that resulted in a value that LOAD choked on. The 
<] tradeoff was made really early on in the R3 project to solve that 
issue. The alternative would be to make MOLD mold [<] as [< ], or 
more specifically to make < mold as "< ", with an extra space every 
time.

in R3 and pre-a97 R3 -> in R2 and pre-a97 R3

I would add it's easy bypassed in R2 if one insert a blank after 
<
>> [<  ]
==[<]

The way MOLD is written, the values are molded by code that doesn't 
know it's in a block. You could have the ] handling code check against 
a charset of iffy characters and then optionally insert an extra 
space if found, but that doesn't deal with user-written code where 
[>] works and [<] doesn't. The usage of ] as the first character 
in a tag is so rare that it's not a bad tradeoff to make.

Well, I agree

Introducing email! datatype next.

form: '?[*-:-*'] 
':' may be in the first position only
'<' can't be in the first position
'%FF' escaping chars in hexa notation

Both R2, R3

escape-uri: [#"%" 2 hex-digit]
email-char: complement union charset {%@:} termination-char
email-syntax: [
	[#":" | not #"<" email-char | escape-uri]
	any [email-char | escape-uri]
	#"@"
	any [email-char | escape-uri]
	termination
]

Hmm, when : is in the first position, a : can occur anywhere afterwards 
as well.

For example, [:a:@:b:]

not anymore an email! but an url! then

Not in R3.

right

right

right

good catch, true in R2 also

Arg, It will be hard to keep the rule tight

I figure that we should look at the email formatting standard, then 
subtract support for any syntax that would conflict with something 
else in REBOL, especially if that doesn't commonly show up in actual 
email addresses. We've already made some tradeoffs in favor of email 
(i.e. no @ in issues or words), maybe we want to make more.

Where would we "want" to do that?

Doesn't work for R2 though - that syntax just needs to be documented, 
it can't be changed.

Or how would such a desire reflect?

In filing CC issues?

When I was trying to replicate the R3 word syntax, it was partly 
to document R3, partly to serve as the basis of a more flexible TRANSCODE 
that would allow people to handle more sloppy syntax without removing 
the valuable errors from the regular TRANSCODE, but mostly it served 
to generate new CC tickets for syntax bugs that we weren't aware 
of because the syntax wasn't well enough documented, and they hadn't 
come up in practice yet.

There is a large, unknown number of such bugs in URL syntax, for 
instance. I wouldn't be surprised if that is the case with email 
too.

If it's obvious bugs, that's comparatively easy, yes.

Your initial message above sounded more like wishes towards a more 
restricted email!.

A more thorough examination of the syntax makes more of these bugs 
obvious.

I don't necessarily want a more restricted email! than it is already, 
but if we are expanding what is possible with email!, it will still 
likely need to be restricted relative to the email standard.

We are not expanding anything :) We are just describing what syntactical 
rules the REBOL email! literal syntax follows.

I'm a little more concerned with R3 URL syntax though, since in that 
case there are real bugs that have already affected people in real 
cases, and because hypothetically a lot of the bugs are fixable in 
mezzanine code.

And as the email! datatype can be used for many a purpose within 
dialects, it does not necessarily have to match RFC822 (or rather 
5322) exactly.

but the syntax checking can't be corrected witth mezzs right ?

(Which would be a relatively complex problem anyway ...

http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html)

Steeve: For emails, no. For urls, yes.

For url! the syntax checking is mostly done by the DECODE-URL mezzanine. 
We can't change what is recognized as a url! by REBOL, but we can 
change how the data is treated once it's recognized. There are errors 
in escape handling, for instance.

Corrected version, works with R2 and R3:

escape-uri: [#"%" 2 hex-digit]
email-char: complement union charset {%@:} termination-char
email-esc: [email-char | escape-uri]
email-syntax: [
	[
		#":" any [email-esc | #":" ] #"@" any [email-esc | #":" ]
		| not #"<" some email-esc #"@" any email-esc
	]
	termination
]

Ah, was wondering. So we can't change the syntax or url!s in R3 as 
well, we can only improve/bugfix url! handling.

You'd be surprised at how flexible the syntax of url! is in R3 :)

I don't think I would.

Fair enough. But if you can figure out exactly hor MOLD handles escaping 
of urls, that would help narrow down what bugs we can fix in DECODE-URL.

hor -> how