(j3.2006) Did we intend to prohibit this?

[Bill Long]

On Mar 10, 2017, at 5:17 PM, Van Snyder <Van.Snyder at jpl.nasa.gov> wrote:

> On Fri, 2017-03-10 at 17:12 -0500, Steve Lionel wrote:
>> On 3/10/2017 5:00 PM, Van Snyder wrote:
>>> According to 9.7.3.2p4, whatever the function result is, it must be
>>> allocatable, or it couldn't be deallocated.
>> 
>> The difference is that the programmer is not in control of the 
>> allocatable object once the function returns. As Tom says, you can see 
>> the value, but don't have a handle on the allocation. The processor is 
>> responsible for setting up the result variable as allocatable and 
>> deallocating it when the statement completes. You don't get to do 
>> anything to its allocation status or even reference it as if it were an 
>> allocatable.
>> 
>> As Malcolm wrote, the purpose of this feature is to allow a function to 
>> return an arbitrary-shape result, the shape of which is then used in the 
>> context of the function's value. Once the function returns, the fact 
>> that the result is allocatable is invisible to the programmer.
> 
> I wasn't able to deduce any of this from the standard.  The standard
> natters on about deallocating an allocatable function result as if it
> actually is allocatable.

There is a local variable in the function that is the function result variable.  If that is declared allocatable, then that variable is what gets deallocated.  The result of the function is a value.  Values are not deallocated, as they can?t have the allocatable attribute.  I don?t think it is any more complicated that that.

Cheers,
Bill


> 
>> Steve
>> 
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> 
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Bill Long                                                                       longb at cray.com
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