Hi there,

I'm a bit of a D newbie (C/C++/C# background), and I apologize if this has been discussed before. I searched the archives and didn't find anything, though. By the way, I absolutely love the language and I only hope I can help to make it even better.

Anyway, I was wondering if perhaps the (very practical) "shortcut" form of the ternary/trinary (?:) operator could be added to the D spec/implementation. This feature originated as a GNU-C extension, and essentially allows for the omission of the second operand. For example:

x = y ? y : z;

Could be shortened to (becomes the same as):

x = y ?: z;

This is a silly, trivial example, but for operands with side effects it becomes quite useful. Consider the following (given the shortcut form is available):

string setting = readline() ?: "default value";

Otherwise, you'd have to go with the much wordier (and less aesthetic):

string input = readline();

if (input) {
setting = input;
}
else {
setting = "default value";
}

In addition, I don't generally see any drawbacks to implementing this feature, barring some horrible lexical ambiguity that I'm not aware of. Is this something that has been considered? Anything I can do to help make it happen?

Thanks for your time,
--AJG.

================================
2B || !2B, that is the question.

This is useful, indeed.  Perl, iirc, generally implements this (very confusingly, imho) as "or".

But, you can shorten your example as follows:

string setting = readline();
if (!setting)
	setting = "default value";

So, it's not quite as bad as your example makes it look, in my opinion, but it's still a lot more cumbersome than the one-liner.

-[Unknown]


> Hi there,
> 
> I'm a bit of a D newbie (C/C++/C# background), and I apologize if this has been
> discussed before. I searched the archives and didn't find anything, though. By
> the way, I absolutely love the language and I only hope I can help to make it
> even better.
> 
> Anyway, I was wondering if perhaps the (very practical) "shortcut" form of the
> ternary/trinary (?:) operator could be added to the D spec/implementation. This
> feature originated as a GNU-C extension, and essentially allows for the omission
> of the second operand. For example:
> 
> x = y ? y : z;
> 
> Could be shortened to (becomes the same as):
> 
> x = y ?: z;
> 
> This is a silly, trivial example, but for operands with side effects it becomes
> quite useful. Consider the following (given the shortcut form is available):
> 
> string setting = readline() ?: "default value";
> 
> Otherwise, you'd have to go with the much wordier (and less aesthetic):
> 
> string input = readline();
> 
> if (input) {
> setting = input;
> }
> else {
> setting = "default value";
> }
> 
> In addition, I don't generally see any drawbacks to implementing this feature,
> barring some horrible lexical ambiguity that I'm not aware of. Is this something
> that has been considered? Anything I can do to help make it happen?
> 
> Thanks for your time,
> --AJG.
> 
> ================================
> 2B || !2B, that is the question.

I definitely see the use in shortening that syntax, but the ?: together just doesn't look appealing/intuitive to me.  I suppose it is the best choice for the shortened operator, but !: would make more sense to me... It's more like "if NOT this, then do this".  ?: on first appearance would look like "if this, then do this".

In article <d87p0o$2o39$1@digitaldaemon.com>, Unknown W. Brackets says...
>
>This is useful, indeed.  Perl, iirc, generally implements this (very confusingly, imho) as "or".
>
>But, you can shorten your example as follows:
>
>string setting = readline();
>if (!setting)
>	setting = "default value";
>
>So, it's not quite as bad as your example makes it look, in my opinion, but it's still a lot more cumbersome than the one-liner.
>
>-[Unknown]
>
>
>> Hi there,
>> 
>> I'm a bit of a D newbie (C/C++/C# background), and I apologize if this has been discussed before. I searched the archives and didn't find anything, though. By the way, I absolutely love the language and I only hope I can help to make it even better.
>> 
>> Anyway, I was wondering if perhaps the (very practical) "shortcut" form of the ternary/trinary (?:) operator could be added to the D spec/implementation. This feature originated as a GNU-C extension, and essentially allows for the omission of the second operand. For example:
>> 
>> x = y ? y : z;
>> 
>> Could be shortened to (becomes the same as):
>> 
>> x = y ?: z;
>> 
>> This is a silly, trivial example, but for operands with side effects it becomes quite useful. Consider the following (given the shortcut form is available):
>> 
>> string setting = readline() ?: "default value";
>> 
>> Otherwise, you'd have to go with the much wordier (and less aesthetic):
>> 
>> string input = readline();
>> 
>> if (input) {
>> setting = input;
>> }
>> else {
>> setting = "default value";
>> }
>> 
>> In addition, I don't generally see any drawbacks to implementing this feature, barring some horrible lexical ambiguity that I'm not aware of. Is this something that has been considered? Anything I can do to help make it happen?
>> 
>> Thanks for your time,
>> --AJG.
>> 
>> ================================
>> 2B || !2B, that is the question.

Regards,
James Dunne

James Dunne says...
>I definitely see the use in shortening that syntax, but the ?: together just doesn't look appealing/intuitive to me.  I suppose it is the best choice for the shortened operator, but !: would make more sense to me... It's more like "if NOT this, then do this".  ?: on first appearance would look like "if this, then do this".

That's actually not a bad idea. I'd be happy to see the feature implemented with either of the two forms (with '?' or with '!'). In addition, in GNU-C, the two tokens don't have to go together, so it's somewhat flexible. E.g.:

x = y ? : z;

or:

x = y ? /* y */ : z;

or, with this new idea:

x = y ! : z;

Cheers,
--AJG.

>In article <d87p0o$2o39$1@digitaldaemon.com>, Unknown W. Brackets says...
>>
>>This is useful, indeed.  Perl, iirc, generally implements this (very confusingly, imho) as "or".
>>
>>But, you can shorten your example as follows:
>>
>>string setting = readline();
>>if (!setting)
>>	setting = "default value";
>>
>>So, it's not quite as bad as your example makes it look, in my opinion, but it's still a lot more cumbersome than the one-liner.
>>
>>-[Unknown]
>>
>>
>>> Hi there,
>>> 
>>> I'm a bit of a D newbie (C/C++/C# background), and I apologize if this has been discussed before. I searched the archives and didn't find anything, though. By the way, I absolutely love the language and I only hope I can help to make it even better.
>>> 
>>> Anyway, I was wondering if perhaps the (very practical) "shortcut" form of the ternary/trinary (?:) operator could be added to the D spec/implementation. This feature originated as a GNU-C extension, and essentially allows for the omission of the second operand. For example:
>>> 
>>> x = y ? y : z;
>>> 
>>> Could be shortened to (becomes the same as):
>>> 
>>> x = y ?: z;
>>> 
>>> This is a silly, trivial example, but for operands with side effects it becomes quite useful. Consider the following (given the shortcut form is available):
>>> 
>>> string setting = readline() ?: "default value";
>>> 
>>> Otherwise, you'd have to go with the much wordier (and less aesthetic):
>>> 
>>> string input = readline();
>>> 
>>> if (input) {
>>> setting = input;
>>> }
>>> else {
>>> setting = "default value";
>>> }
>>> 
>>> In addition, I don't generally see any drawbacks to implementing this feature, barring some horrible lexical ambiguity that I'm not aware of. Is this something that has been considered? Anything I can do to help make it happen?
>>> 
>>> Thanks for your time,
>>> --AJG.
>>> 
>>> ================================
>>> 2B || !2B, that is the question.
>
>Regards,
>James Dunne

================================
2B || !2B, that is the question.

Alvaro Gutierrez wrote:
<snip>
> Anyway, I was wondering if perhaps the (very practical) "shortcut" form of the
> ternary/trinary (?:) operator could be added to the D spec/implementation. This
> feature originated as a GNU-C extension, and essentially allows for the omission
> of the second operand. For example:
<snip>
> string setting = readline() ?: "default value";

Like a generalisation of ||.  I guess that || could be enhanced to do this (at the moment it just returns a boolean value), but I'm thinking it would complicate the process of detecting the '=' instead of '==' typo.

> Otherwise, you'd have to go with the much wordier (and less aesthetic):
> 
> string input = readline();
> 
> if (input) {
> setting = input;
> }
> else {
> setting = "default value";
> }

Assuming that string is an alias for a char[], then you can compromise

    string input;
    setting = (input = readline()) != "" ? input : "default value";

Stewart.

-- 
My e-mail is valid but not my primary mailbox.  Please keep replies on the 'group where everyone may benefit.

"Stewart Gordon" <smjg_1998@yahoo.com> wrote in message news:d89pcp$1q6v$1@digitaldaemon.com...
> Alvaro Gutierrez wrote:
> <snip>
>> Anyway, I was wondering if perhaps the (very practical) "shortcut" form
>> of the
>> ternary/trinary (?:) operator could be added to the D
>> spec/implementation. This
>> feature originated as a GNU-C extension, and essentially allows for the
>> omission
>> of the second operand. For example:
> <snip>
>> string setting = readline() ?: "default value";
>
> Like a generalisation of ||.  I guess that || could be enhanced to do this (at the moment it just returns a boolean value), but I'm thinking it would complicate the process of detecting the '=' instead of '==' typo.

Let's call the new operator |||
just kidding.

On Thu, 9 Jun 2005 15:05:26 +0000 (UTC), Alvaro Gutierrez wrote:

> James Dunne says...
>>I definitely see the use in shortening that syntax, but the ?: together just doesn't look appealing/intuitive to me.  I suppose it is the best choice for the shortened operator, but !: would make more sense to me... It's more like "if NOT this, then do this".  ?: on first appearance would look like "if this, then do this".
> 
> That's actually not a bad idea. I'd be happy to see the feature implemented with either of the two forms (with '?' or with '!'). In addition, in GNU-C, the two tokens don't have to go together, so it's somewhat flexible. E.g.:
> 
> x = y ? : z;
> 
> or:
> 
> x = y ? /* y */ : z;
> 
> or, with this new idea:
> 
> x = y ! : z;

Just to clarify, the proposed syntax is equivalent to ...

  if (!(y)) x = z;

right? Which is three characters longer.
-- 
Derek Parnell
Melbourne, Australia
10/06/2005 6:46:51 AM

Derek Parnell wrote:

> On Thu, 9 Jun 2005 15:05:26 +0000 (UTC), Alvaro Gutierrez wrote:
> 
>> James Dunne says...
>>>I definitely see the use in shortening that syntax, but the ?: together
>>>just
>>>doesn't look appealing/intuitive to me.  I suppose it is the best choice
>>>for the shortened operator, but !: would make more sense to me... It's
>>>more like "if NOT
>>>this, then do this".  ?: on first appearance would look like "if this,
>>>then do this".
>> 
>> That's actually not a bad idea. I'd be happy to see the feature implemented with either of the two forms (with '?' or with '!'). In addition, in GNU-C, the two tokens don't have to go together, so it's somewhat flexible. E.g.:
>> 
>> x = y ? : z;
>> 
>> or:
>> 
>> x = y ? /* y */ : z;
>> 
>> or, with this new idea:
>> 
>> x = y ! : z;
> 
> Just to clarify, the proposed syntax is equivalent to ...
> 
>   if (!(y)) x = z;
> 
> right? Which is three characters longer.

No. The proposed syntax is equivalent to:
 x = y ? y : z;
but with only one evaluation of y.

I use this feature extensively in another language where || has this behaviour. E.g:

string message = query_message() || "Default";

ob = get_object() || new Ob;

It is neat and useful, but maybe more so in dynamically typed languages.

On Thu, 09 Jun 2005 23:47:05 +0000, Oskar Linde wrote:

> Derek Parnell wrote:
> 
>> On Thu, 9 Jun 2005 15:05:26 +0000 (UTC), Alvaro Gutierrez wrote:
>> 
>>> James Dunne says...
>>>>I definitely see the use in shortening that syntax, but the ?: together
>>>>just
>>>>doesn't look appealing/intuitive to me.  I suppose it is the best choice
>>>>for the shortened operator, but !: would make more sense to me... It's
>>>>more like "if NOT
>>>>this, then do this".  ?: on first appearance would look like "if this,
>>>>then do this".
>>> 
>>> That's actually not a bad idea. I'd be happy to see the feature implemented with either of the two forms (with '?' or with '!'). In addition, in GNU-C, the two tokens don't have to go together, so it's somewhat flexible. E.g.:
>>> 
>>> x = y ? : z;
>>> 
>>> or:
>>> 
>>> x = y ? /* y */ : z;
>>> 
>>> or, with this new idea:
>>> 
>>> x = y ! : z;
>> 
>> Just to clarify, the proposed syntax is equivalent to ...
>> 
>>   if (!(y)) x = z;
>> 
>> right? Which is three characters longer.
> 
> No. The proposed syntax is equivalent to:
>  x = y ? y : z;
> but with only one evaluation of y.

Thanks, I got a bit lost there for awhile.

So using standard syntax it's sort of like ...

 if ( ((x = y) == false) x = z;

The difference being that this has two assignments rather than one.

> I use this feature extensively in another language where || has this behaviour. E.g:
> 
> string message = query_message() || "Default";
> 
> ob = get_object() || new Ob;
> 
> It is neat and useful, but maybe more so in dynamically typed languages.

Yes, I can see that it might be a neat shortcut at times. It would just have to be another idiom for people to learn how to read.

How about a more familiar sort of syntax ...

  ob =? get_object() : new Obj;

To me, this implies an assignment that is conditional and is analogous to

  x ? y : z;


-- 
Derek
Melbourne, Australia
10/06/2005 8:38:02 AM

Derek Parnell wrote:

> How about a more familiar sort of syntax ... 
> 
>   ob =? get_object() : new Obj;

What about this:

ob ?= get_object() : new Obj;

?= by analogy with += *= etc.

James McComb