Help on operators in Dolphin

Hi,

Occasionally I find reference to ##(self) and ##(icon) etc, and I've
tried to find what it is.
In a workspace #(self) returns an array, and ##(self) return an
UndefinedObject, but I don't quite get it. Would I be right in assuming
## is a special method?

Is there any ware in Help a details explanation of special operators
and symbols. eg / // # ## ^ etc (I know some but not all of the uses)?

Thanks Theo

Theo,

> Occasionally I find reference to ##(self) and ##(icon) etc, and I've
> tried to find what it is.
> In a workspace #(self) returns an array, and ##(self) return an
> UndefinedObject, but I don't quite get it. Would I be right in
> assuming ## is a special method?
>
> Is there any ware in Help a details explanation of special operators
> and symbols. eg / // # ## ^ etc (I know some but not all of the uses)?

A quick Google reveals this thread (amonst others) that explains the
##() syntax:

http://groups.google.com/group/comp.lang.smalltalk/browse_frm/thread/b56
30d99756c232b/2482c82d815c9dba?lnk=st&q=dolphin+smalltalk+%23%23+constan
t&rnum=1#2482c82d815c9dba

Best regards,

--
Andy Bower
Dolphin Support
www.object-arts.com

> Is there any ware in Help a details explanation of special operators
> and symbols. eg / // # ## ^ etc (I know some but not all of the uses)?

#(self) creates a literal array with the literal symbol #self as the single
element.

However, ##(self) is sort of like, a compile time inline. Basically the
message/object gets evaluated at compile time rather than runtime. so you
can do something like:

| secondsInAWeek |
secondsInAWeek := ##(60 * 60 * 24 * 7).

And instead of being evaluated every time the message it is contained within
is invoked, it is evaluated once, at compile time, so the actual bytecode
that is generated, is the same as if you had used a magic number constant
like so:

| secondsInAWeek |
secondsInAWeek := 604800.

##() doesn't work in a workspace, only in compiled methods.

Andy Bower wrote:

> A quick Google reveals this thread (amonst others) that explains the
> ##() syntax:

Can you suggest search terms for Google /without/ knowing what the ##(...)
construct means in advance ?

    -- chris

Sean,

> ##() doesn't work in a workspace, only in compiled methods.

Small correction -- ##( ... ) does work in workspaces.  The only difference is
that "self" is bound to nil in a workspace so ##( self ) will evaluate to nil
there.  In a method ##( self ) will evaluate to the class where the method is
defined -- there's no profundly logical reason why that should be the case, but
it's handy that /at compile time/ self evaluates to the class.

    -- chris

> Small correction -- ##( ... ) does work in workspaces.  The only
> difference is
> that "self" is bound to nil in a workspace so ##( self ) will evaluate to
> nil
> there.

Hey Chris,

Whoops! I think I tried to evaluate some ##() code once in a workspace in
Dolphin 5 and it didn't work. I can't remember the exact reason, but it left
me with the impression that it didn't work in a workspace, hence my
eagerness to perpetuate that myth. Thanks for pointing that out.

Regards,

Sean

Chris,

> > A quick Google reveals this thread (amonst others) that explains the
> > ##() syntax:
>
> Can you suggest search terms for Google without knowing what the
> ##(...) construct means in advance ?

Well I used "dolphin smalltalk ## syntax" as a search term for Google
Groups. It's the second item in the list.

Best regards

--
Andy Bower
Dolphin Support
www.object-arts.com

Andy,

> > Can you suggest search terms for Google without knowing what the
> > ##(...) construct means in advance ?
>
> Well I used "dolphin smalltalk ## syntax" as a search term for Google
> Groups. It's the second item in the list.

Only a coincidence, I'm afraid, Google ignores the ## bit.  If you repeat the
test without the ## you get exactly the same results...

    -- chris

Theo,
If you're new to ST and DST like me, you'll find Bill Schwab's DSDN
application and Ian Bartholomew's newsgroup archive (which you unzip to
the DSDN\Archive directory) invaluable. (Also grab Ian's Chunk Browser
if you haven't http://www.smalltalk.vispa.com/idbchunkbrowser.html)
You can get DSDN here:
http://needle.anest.ufl.edu/anest4/bills/DSDN_news.htm
And the newsgroup archives here:
http://www.smalltalk.vispa.com/newsarchive.html

These tools are the only reason I haven't been hounding these people
daily ;)

Theo,

> Is there any ware in Help a details explanation of special operators
> and symbols. eg / // # ## ^ etc (I know some but not all of the uses)?

It's a bit difficult to judge what is or isn't well known and understood
in Dolphin, but here's a couple that might not be common knowledge ...


#[1 2 3 4 5]
as #(1 2 3 4 5) but answers a ByteArray - so the contents must be
Integers between 0 and 255


1 -> 2
Answers an Association with a key (of 1) and a value (of 2)

--
Ian

Use the Reply-To address to contact me (limited validity).
Mail sent to the From address is ignored.

"Chris Uppal" <[hidden email]> wrote in message
news:43aaaa22$0$260$[hidden email]...
OT but tangential:
I can remember years ago I had a heck of a time searching Google for "DVD+R"
information.  There was no way I could limit the search to only pages that
actually mentioned DVD+R.  I actually wrote to Google to explain the issue,
and they replied that it was a limitation to their index.  Ever since
product names that include novel non-alphanumeric characters always annoy
me. ;)  It looks like the "DVD+R" issue still exists.  I think they should
consider an index enhancement to accommodate at least the more common of
these special cases. "##(" might not be common enough, but certainly "DVD+R"
would be.

Chris

> Sean
> However, ##(self) is sort of like, a compile time inline. Basically the
> message/object gets evaluated at compile time rather than runtime.

So ##(... is like a compiler directive?
Theo

John,
I've been playing with Smalltalk for years, but only get to work with
it as a hobby. My income comes from AS/400 and RPG quite different. So
I never quite get to remember all of the little special thing and often
have to rediscovering them.
Thanks Theo

Andy,
This is a wish list: can you add a section to help with special
operators and/or compiler directives? eg in Excel help when you select
"operators" you get a nice little overview on + - / etc

Possibly under appendix A called "Operators" or "Compiler directives"
etc
showing + / - // ##() #() #[] ##[] -> etc with a short explanation and
some examples
Thanks, Theo

Christopher J. Demers wrote:
>  I think they should consider an index enhancement to accommodate
> at least the more common of these special cases. "##(" might not be
> common enough, but certainly "DVD+R" would be.

Some of the other search engines do index each character.  I believe that
anything based on the FAST engine does, but I don't know which search portals
use it.  Unfortunately only Google indexes Usenet -- on the rare occasions
where hasn't trashed its records.  Fortunately there's Ian's archive, and a
quick check of that reveals 159 hits for ##( between 1997-04-01 and 2005-10-28.

Thanks Ian !

    -- chris