Re: question about functions

["Matthew Heaney" <matthew_heaney@acm.org>]

In article <3889A56C.61C4@nospam.com.tj> , Andy <andy@nospam.com.tj>  
wrote:

>> One alternate approach that is possible in Ada is to pass the result
>> as an 'out' parameter :
>>
>> procedure f (A, B : in T; C : out T);
>>
>> now you can do C'Address.
>>
> But this would give the address of the formal parameter which
> may not be the address of the actual parameter. Unless T is a
> tagged type, isn't the compiler free pass parameters by
> reference or value?

Certain types are guaranteed to be passed by reference.  By-reference
types include tagged types and limited types.  (Note that a limited type
doesn't have to be tagged to be passed by reference.)

Scalar types must be passed by value.

The language doesn't specify whether composite types (nonlimited records
arrays) are passed by reference or by value.

If you want to take the address (here, C'Address) of a subprogram
parameter, the parameter must be a by-reference type: either tagged or
limited.

See RM95 13.3 (16).

--
Philosophy may be ignored but not escaped; and those who most ignore
least escape.

David Hawkins