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Arnold Neumaier wrote:
Just to make my point clear, and make sure we agree: if IEEE-1788 requires being able to parse the text of expressions in the format specified in 2.6, then I find it not language-level-friendly. It would be a boring-to-implement and useless requirement (and not constexpr-friendly for the particular case of C++0x). Specifying I/O text/literals formats for isolated intervals is fine, but going to expressions is too much, IMO. Languages already have their own ways and syntax to specify expressions, we should just talk about expressions in a more abstract way than text format in IEEE-1788.The next version of my proposal will have the conversion of text containing constant expressions only as recommendation, except for the conversion of quotients of arbitrary integers, which will be required to convert to the tightest interval containing the quotient.
I guess I will then have to ask for a paragraph in the Rationale which explains "why this one?" :)
In addition, it will specify the following about value-changing optimizations: Value-changing optimizations. These should be handled similar to Section 10.4 of IEEE-754-2008. Transformations are allowed if and only if they would be exact in exact real arithmetic and provably lead to enclosures contained in the enclosures obtained by using the original expression. A (nonexhaustive) list of such allowed transformations should be provided in an appendix to the standard. Does this satisfy you?
Fine with me. Thank you Arnold. -- Sylvain Pion INRIA Sophia-Antipolis Geometrica Project-Team CGAL, http://cgal.org/
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