Re: Ada.Locales pseudo-string types

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 12-08-08 10:18 , Dmitry A. Kazakov wrote:
> On Wed, 08 Aug 2012 10:04:37 +0300, Niklas Holsti wrote:
> 
>> The rule does seem surprisingly rigid, for a value conversion. (The
>> Annotated RM does not explain or motivate it.)
> 
> Ada didn't appreciate structured type equivalence in earlier times. These
> rules were designed before anonymous access types crept in.

But we are talking about explicitly requested type conversions, not
implicit type equivalence. As I understood it, at least.

>> For a value conversion,
>> the default could be to convert element by element, and the compiler
>> could then optimize this conversion based on what it can deduce
>> statically about the matching of the source and target subtypes.
> 
> Could be interesting when elements themselves are arrays of discriminated
> record subtypes constrained via discriminants with array components again
> constrained etc.

Sure, but this should not require much new intelligence in the compiler.
An array type conversion of the form A1 := A1_Type(A2); could just as
well be written as an explicit loop with explicit element-by-element
conversions, A1(I) := A1_Element_Type(A2(I)). A compiler could do this
expansion internally, giving code that is legal today and which the
compiler should already be able to compile.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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