Peter Michaux wrote: > On Sat, Nov 15, 2008 at 11:18 PM, Peter Michaux <[EMAIL PROTECTED]> wrote: > >> Also is it "should" or "must"? RFC documents are usually very strict >> about defining "should" etc and I don't see a definition of "should" >> before page 41 of the pdf where this use occurs. > > http://www.ietf.org/rfc/rfc2119.txt > > I think explicitly adopting these definitions would be a good step in > improving the clarity of the ECMAScript standard.
I advise caution here: many, perhaps most of the existing uses of "must" or "must not" in ECMA-262 or the Kona draft are not consistent with the RFC2119 definitions. The RFC2119 meaning of MUST is a mandatory conformance requirement on implementations of the protocol or format defined in the RFC. For a programming language spec, it is ambiguous whether this means a requirement on valid programs, or a requirement on the language implementation. It's important for those to be distinguished. ECMA-262 and Kona use "must" sometimes as a requirement on the language implementation, but at least as often to mean a property that is necessarily logically true (or false for "must not"), assuming that the spec is self-consistent -- that is, a tautology or an implication of other requirements, not an independent conformance requirement. For example: If a mathematical operation or function is applied to a floating-point number, it should be understood as being applied to the exact mathematical value represented by that floating-point number; such a floating-point number must be finite, and if it is +0 or 0 then the corresponding mathematical value is simply 0. This use of "must" is an assertion that the *specification* never calls for a mathematical operation or function to be applied to an infinite or NaN value (so if it did, that would be a specification bug); not that an implementation is required not to do so. -- David-Sarah Hopwood _______________________________________________ Es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
