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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Locales pseudo-string types
Date: Wed, 08 Aug 2012 14:44:48 +0300
Organization: Tidorum Ltd
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Date: 2012-08-08T14:44:48+03:00
List-Id: <comp.lang.ada>

On 12-08-08 11:33 , J-P. Rosen wrote:
> Le 08/08/2012 10:17, Niklas Holsti a �crit :
>>> And of course, it would force pass-by-copy
>>
>> I don't think so. If the source and target element subtypes statically
>> match, 
> then the conversion is allowed

Yes, and for sure the compiler could detect this case, and use the fast
code. So it would not have to make a copy.

>> or match well enough that no element conversions are necessary
>> (as in the original Ada.Locales example), the compiled code could be the
>> same as compilers use now.
> But they won't match the other way round, and passing a conversion to
> in-out parameters requires two-way conversion

That is a view conversion. I was talking about value conversions, as was
the original poster, I believe.

>> In other cases, the compiler could create a
>> temporary array to hold the result of the conversion, and pass this
>> array by reference.
> If you make a copy and pass it by reference, I would call it pass by
> copy ;-)

What you call a "copy" is the result of converting the array. If the
conversion rules are relaxed, this may not be an exact bit-by-bit copy
of the original array any more (for example, if conversion from integer
elements to float elements is allowed).

This is just the same as when the actual parameter is a function call
that returns an array type. The result of the function can be passed by
reference, although the object is no doubt a temporary one.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .