World: r3wp

The whole issue is caused by the fact, that Carl decided to "hide" 
some issues, that are "more honestly exposed" by other programming 
languages. Usually it looks, like the "arithmetic hiding in REBOL" 
helps, but there are cases like this, where the result of hiding 
is worse, than if the arithmetic was "honest".

Thanks, Ladislav. You nailed it better, than I could. About the last 
digits, I meant, that we can count on 15-17 decimal digits of precision. 
I guess, it's more precise to say, that the decimal! datatype has 
15.95 decimal digits of precision.
See: http://en.wikipedia.org/wiki/IEEE_754-2008#Basic_formats


For the new ones, an often used example, where math with IEEE 754 
floats (in all languages) gives unexpected result is:

>> 0.1 + 0.2 - 0.3
== 5.55111512312578E-17

I guess, it's more precise to say, that the decimal! datatype has 
15.95 decimal digits of precision.

 - the most precise is to say, that it has (usually) 53 binary digits 
 of precision. That can be "transformed" to 15.95, but such a "transformation" 
 is quite uniformative, since it ignores some important facts

Fact #1: the representation is binary, and it cannot represent exactly 
even the numbers representable using just one decimal digit

Fact#2: 16-digit decimal numbers cannot be used to represent "exactly 
enough" the IEEE754 binary numbers

(to not confuse the reader, I should have used "precisely enough" 
instead of "exactly enough" in the above fact#2 statement)

why is , not valid word?

>> type? '.
== word!
>> type? ', 
** Syntax Error: Invalid word -- ',
** Near: (line 1) type? ',

Assumably because the opinion was/is, that commas make programs less 
readable. I see no other reason.

I see it absolutely cruicial that there aren't commas between elements 
[ 1 2 3 ] NOT [ 1, 2, 3 ].. but this has nothing to do why , couldn't 
be a valid word of a dialect for example if . ` (for example) are 
IMHO

(I suspect it's used somewhere, but I don't see it .. like % or $ 
is not a valid word since they are part of file / money format ( 
not that parser couldn't be made a little smarter and still allow 
it))

Good question... I was asking as well long time ago http://www.rebol.org/ml-display-message.r?m=rmlDRXJ

Geomol, you are the winner! That is the official reason. Plus, ,0 
is the same as 0.0 since , can be used as a decimal separator.

so any program that has , anywhere is ugly so we ban them.. it's 
no use in complaining, but that doesn't make sense to me.

now my dialect that consumes sql has dots instead of commas [ select 
user.id . user.* from user where id = #myid and name = #name ] .. 
I will surviwe but I will hardly impress any geeks to rebol with 
it as I otherwise could :)

Oldes, I'm on linux where I can't copy poaste that url from altme 
or click it (I don't know why linux doesn't fix dual copy paste and 
istead focuses of various fancy stuff)

So I will reply later when I can

If comma is allowed as word, decision has to be made, what to do 
with things like ,0 as Brian point out. Either anything starting 
with a comma should be words (easy to implement, but might give unpredicted 
result to users trying to writing decimals starting with a comma) 
or a special rule should be made, so it's a decimal, if the comma 
is only followed by digits, else it's a word (harder to implement).

You also need to handle things like:
,000'000e+4
which is simple 0.0 today.

To me, not having comma is a problem in that certain types of data 
become much harder to load.

This is also strange:
b: to-block ";"
length? b
== 0

even:
b: to-block ";;;;;;;"

I think these issues are related to parse, as coma and semicolon 
are default separater for parse.

actually not strange, since to-block converts the string into REBOL 
data, so it's interpreted as an inline comment. I think the behavior 
is correct.

I see, that's correct. I missed that semicolon is for commenting.

TO-BLOCK can be seen as a cheap version of LOAD, AFAIK.

Much cheaper on R3 than R2 - LOAD does a lot of work. Note that TO-BLOCK 
doesn't bind any words in the resulting block, which can come in 
handy sometimes.

thanks, I would I ask what is the difference :)

TO BLOCK! is much safer on untrusted data as well.

what is risk if I use load?

The comma being disallowed as a word does mean you can't use it literally 
i true dialects, but that doesn't prevent you from writing a DSL 
and using string parsing. There have to be lines drawn somewhere.

LOAD used to evaluate headers aggressively, though I don't think 
it does any more under R2. I'm not sure about R3, but I imagine Brian 
has made sure that's safe.

Janko: If you right-click the URL, it says "Copied to clipboard" 
- it means the X clipboard, which you paste from in Linux by using 
middle-click

Izkata: wow .. it works! :)

Oldes: I read the discussion on mailing list. Obviously I agree with 
you (in fact our reasoning is like copied:)

Gabriele interestingly subverted your reasoning by "you can't expect 
REBOL to be able to parse into REBOL values any syntax", but that 
is not the reasoning here :) . Reasoning is simple why rebol isn't 
more consistent and

(pressed the submit by accident).. reasoning is:

If consistency good?

if . is word why isn't ,?
you mentioned that it's because:
>> ,012
== 0.012

but that fails since this also works :)
>> .012
== 0.012

but I know there are more prominent things to change/fix (if any 
will get fixed at all) that I don't realistically expect anything 
changed about this in near future (but that sql dialect would be 
much cooler if it werent for , exception)

index.html is a useful word, index,html is not.

there has to be a place where you draw the line... will you ask for 
$ next? what about #? What about ' ? or : ? or even ; ?

some characters are reserved for a reason. if you're parsing another 
language, use string parsing. LOAD is supposed to parse REBOL, not 
other languages.

' can be used in words like:

>> can't: 42
== 42
>> can't
== 42

Some would argue, comma is kinda the same.

there is a behaviour difference for LAST function on blocks and lists:
>> b: next next [1 2]
>> last b
** Script Error: Out of range or past end  ;which is ok

>> a: next next make list! [1 2]
>> last a
== 2

But it is not same for FIRST
>> first a ;(or first b)
** Script Error: Out of range or past end ;same for both.

>> a
== make list! []
>> last? a
== false

I'd say its a bug with the list! datatype.

I guess so, because reverse is changing the internal position also:
>> a: make list! [1 2 3]
== make list! [1 2 3]
>> reverse a
== make list! [3 2 1]
>> a
== make list! [1]

it goes to last item in the list. But it doesn't work like that for 
block! values.
>> b: make block! [1 2 3]
== [1 2 3]
>> reverse b
== [3 2 1]
>> b
== [3 2 1]

There is a bug report on Rambo for reverse on list!
http://www.rebol.net/cgi-bin/rambo.r?id=4420&

Geomol, right, so, should we also allow # inside a word? Why not 
allow even [ then?


You have to draw a line somewhere, both to simplify the parser, and 
so that the language is readable. The , has a special meaning in 
basically every language, so it's hard to know what the consequences 
of allowing , would be, even assuming the parser is not affected 
by it.