Re: Meeting the Scope and Purpose of P754

[Vincent Lefevre <vincent@xxxxxxxxxx>]

On 2007-07-18 13:27:44 +0100, Nick Maclaren wrote:
> Vincent Lefevre <vincent@xxxxxxxxxx> wrote:
> > C99 says "semantic type". See also 6.3.1.8#2 and its note about cast
> > and assignment operators.
>
> And where does it define semantic type?  Remember that the C90 (and,
> much more so, C99) introduced the concept of two types that are
> syntactically different but semantically identical.  It is perfectly
> reasonable to say that the semantic type has nothing to do with the
> actual values of a datum.

AFAIK, C99 defines only one concept of type for an expression (6.2.5),
so I don't see any ambiguity.

> Also, according to ISO rules, 6.3.1.8#2 is normative, but its footnote
> is merely informative.

Yes, but it allows to say whether an interpretation can be correct or
not.

> 6.3.1.8#2 does not mention any exceptions, [...]

There doesn't need to be an exception if some other part of the
standard gives more detail. The standard says that a conversion
is required when there is an explicit conversion (6.3.1.5), but
I agree that you need informative parts of the standard to guess
what an explicit conversion is exactly. After this conversion,
6.3.1.8#2 still holds.

-- 
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.org/>
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Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)