(j3.2006) (SC22WG5.4222) What shall we do with the broken feature?

[Dan Nagle]

Hi,

I vote with Bill.

Quick fixes chance errors, processing an Interp allows
time for more in-depth thought.

No one is implementing this today,
we can take the time to do it right.

On Mar 17, 2010, at 4:19 AM, Malcolm Cohen wrote:

> The facility of being able to pass a null pointer or unallocated  
> allocatable to an optional nonpointer nonallocatable dummy argument  
> and have that treated as being an absent dummy argument is broken as  
> follows.
>
> (i) All of the optional DIM arguments to the intrinsic functions  
> that change the rank are qualified with "The corresponding actual  
> argument shall not be an optional dummy argument.".  Previously it  
> was not permitted to pass a null pointer here, now it is permitted  
> and gives a runtime-varying rank depending on the association status  
> of the pointer.  E.g. PRODUCT(matrix,pointer_to_dim) is rank 1 if  
> pointer_to_dim is associated and rank 0 if it is not.  20 functions  
> have a prohibition against optional dummy arguments, but in several  
> of those it is an unnecessary prohibition so fewer than 20 would be  
> necessarily affected.
>
> (ii) This feature appears to change the results of ASSOCIATED when  
> TARGET is a null pointer.  This does not appear on the surface to be  
> fixable other than by specifying that the feature does not apply to  
> this particular intrinsic function, which might be confusing.
>
> (iii) Minor: The performance of a few intrinsic functions such as  
> MAX when some arguments are pointers is adversely affected.
>
> (iv) Nitpick: the description in the Introduction omits the  
> unallocated allocatable case.
>
> How should we address the problem?
> (1) fix the DIS by deleting the feature (I don't think we have a  
> mandate for that though);
> (2) fix the DIS by changing the wording;
> (2) leave it to be fixed later via interpretation processing (other  
> than the nitpick which should be done anyway).
>
> Comments?
>
> Cheers,
> -- 
> ................................Malcolm Cohen, Nihon NAG, Tokyo.
>
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-- 
Cheers!

Dan Nagle