I dont see multiple value returns in D. Wouldnt it be nice to finally have it anywhere else than in scheme? From a logical standpoint,we are already doing it anyway with reference parameters. Its just that something like (y2, error)fct(y1, someArg) would be more clear than just fct(y1, someArgs, y2, err).


newbie1654

lacs wrote:

>I dont see multiple value returns in D. Wouldnt it be nice to finally have it
>anywhere else than in scheme? From a logical standpoint,we are already doing it
>anyway with reference parameters. Its just that something like (y2,
>error)fct(y1, someArg) would be more clear than just fct(y1, someArgs, y2, err).
>
>
>newbie1654
>  
>
This has been discussed before.  Maybe if we're lucky it'll get into 2.0, but I don't see it in 1.0 as there are too many subtle problems.

-- 
-Anderson: http://badmama.com.au/~anderson/

J Anderson wrote:
> lacs wrote:
> 
>> I dont see multiple value returns in D. Wouldnt it be nice to finally have it
>> anywhere else than in scheme? From a logical standpoint,we are already doing it
>> anyway with reference parameters. Its just that something like (y2,
>> error)fct(y1, someArg) would be more clear than just fct(y1, someArgs, y2, err).
>>
>>
>> newbie1654
>>  
>>
> This has been discussed before.  Maybe if we're lucky it'll get into 2.0, but I don't see it in 1.0 as there are too many subtle problems.
> 
Ok I found and read some discussion about it. It seemed a real puzzle because of some stack and overloading considerations. However, just making the compiler considere
float, float foo(in float, in float);
the same as
void foo(in float, in float, out float, out float);
would not be very complicated. Does it really needs to be more sophisticated then that?

lacs schrieb:

> I dont see multiple value returns in D. Wouldnt it be nice to finally have it
> anywhere else than in scheme? From a logical standpoint,we are already doing it
> anyway with reference parameters. Its just that something like (y2,
> error)fct(y1, someArg) would be more clear than just fct(y1, someArgs, y2, err).


Scroll down a bit, this question was asked yesterday or so and i answered extensively.

-eye

On Wed, 21 Apr 2004 17:50:19 -0400, lacs wrote:

> J Anderson wrote:
>> lacs wrote:
>> 
>>> I dont see multiple value returns in D. Wouldnt it be nice to finally
>>> have it
>>> anywhere else than in scheme? From a logical standpoint,we are already
>>> doing it
>>> anyway with reference parameters. Its just that something like (y2,
>>> error)fct(y1, someArg) would be more clear than just fct(y1, someArgs,
>>> y2, err).
>>>
>>>
>>> newbie1654
>>> 
>>>
>> This has been discussed before.  Maybe if we're lucky it'll get into 2.0, but I don't see it in 1.0 as there are too many subtle problems.
>> 
> Ok I found and read some discussion about it. It seemed a real puzzle
> because of some stack and overloading considerations. However, just
> making the compiler considere
> float, float foo(in float, in float);
> the same as
> void foo(in float, in float, out float, out float);
> would not be very complicated. Does it really needs to be more
> sophisticated then that?

I too think that the "Multiple Return Value" issue is just one of syntax and not semantics. It is *just* a way of coding in such a way to make it easy for the code reader/maintainer to see that a routine is returning more than one distinct value. The difference would be ...

  ValA, ValB = foo(inpA, inpB);

as opposed to

  foo(inpA, inpB, ValA, ValB);

which is more clear to readers what the routine is actually doing with the variables used.

-- 
Derek
22/Apr/04 10:43:07 AM

Derek Parnell wrote:

>  ValA, ValB = foo(inpA, inpB);
>
>as opposed to
>
>  foo(inpA, inpB, ValA, ValB);
>
>which is more clear to readers what the routine is actually doing with the
>variables used.
>  
>
A problem with this form is the way the comma operator works.  For example, what you presented is valid code ATM!

int func() { return 0; }

void main()
{
   int a, b;
   a, b = func();
}

Now you could introduce rules to take this out of the language (or change the syntax).  It's just one of the subtle bugs and language changes I was talking about to implement such a thing.

-- 
-Anderson: http://badmama.com.au/~anderson/

Derek Parnell wrote:
> 
>   ValA, ValB = foo(inpA, inpB);
> 

Not to be annoying, but I don't know that I like that syntax.  I think something with parenthesis would be much better... but then, why not just return an array?  It's practically the same thing, isn't it?

PHP, for example, provides a "array extracting" construct, which works as such:

	list ($first_element, $second_element) = array(0 => 1, 1 => 2);

I believe Perl also has this, basically, except it's like this:

	@array = (1, 2);
	($first_element, $second_element) = @array;

But I think that syntax is ulgy too.  I like the "list" construct because it makes it more logical.

	list (ValA, ValB) = foo(inpA, inpB);

-[Unknown]

On Thu, 22 Apr 2004 09:04:07 +0800, J Anderson wrote:

> Derek Parnell wrote:
> 
>>  ValA, ValB = foo(inpA, inpB);
>>
>>as opposed to
>>
>>  foo(inpA, inpB, ValA, ValB);
>>
>>which is more clear to readers what the routine is actually doing with the variables used.
>> 
>>
> A problem with this form is the way the comma operator works.  For example, what you presented is valid code ATM!
> 
> int func() { return 0; }
> 
> void main()
> {
>     int a, b;
>     a, b = func();
> }
> 
> Now you could introduce rules to take this out of the language (or change the syntax).  It's just one of the subtle bugs and language changes I was talking about to implement such a thing.

I'm sorry that I didn't make myself clear. I wasn't suggesting *any* specific syntax, just the concept that a syntax change to support this idea might be worth considering. The example I gave was just to show something - not the precise syntax that D could use. That would need much more discussion yet.

-- 
Derek
22/Apr/04 11:11:09 AM

On Wed, 21 Apr 2004 18:05:04 -0700, Unknown W. Brackets wrote:

> Derek Parnell wrote:
>> 
>>   ValA, ValB = foo(inpA, inpB);
>> 
> 
> Not to be annoying, but I don't know that I like that syntax.  I think something with parenthesis would be much better... but then, why not just return an array?  It's practically the same thing, isn't it?

You are not annoying ;-)

I wasn't promoting any specific syntax, just the idea that a syntax change for D that supports multiple return values might be a useful idea.

> PHP, for example, provides a "array extracting" construct, which works as such:
> 
> 	list ($first_element, $second_element) = array(0 => 1, 1 => 2);
> 
> I believe Perl also has this, basically, except it's like this:
> 
> 	@array = (1, 2);
> 	($first_element, $second_element) = @array;
> 
> But I think that syntax is ulgy too.  I like the "list" construct because it makes it more logical.
> 
> 	list (ValA, ValB) = foo(inpA, inpB);
> 
> -[Unknown]

And I'm sure there are many others out there too.
-- 
Derek
22/Apr/04 11:13:43 AM

Derek Parnell wrote:

>
>I'm sorry that I didn't make myself clear. I wasn't suggesting *any*
>specific syntax, just the concept that a syntax change to support this idea
>might be worth considering. The example I gave was just to show something -
>not the precise syntax that D could use. That would need much more
>discussion yet.
>
>  
>
I would like multiple return types as well. 

There are huge threads earlier on this.  I don't expect you to read them all but there must be at least a dozen different ways of doing multiple return values.

-- 
-Anderson: http://badmama.com.au/~anderson/