Re: P1788 1.8 "Language considerations"

["N.M. Maclaren" <nmm1@xxxxxxxxx>]

I posted some possible changes (actually suggested by other people),
and here is the rest of my response.

There were some problems with this paragraph in 1.8:

   Specifically, if the data before and after the unit of
   transformation is regarded as a set of mathematical intervals, the
   transformed form of all combinations of the elements (the real
   values) represented by the prior set shall be a member of the
   posterior set.

Here is a possible replacement:

   Specifically, a language shall specify a set of bindings to the
   operations specified in this standard, with the functionality and
   semantics as specified here.  These may be specified as bindings
   to built-in operations, library procedures or otherwise.

   Code which is syntactically the same as code operating on
   approximate real numbers, but operating on intervals, shall obey
   the following semantics: if the data before and after the unit of
   transformation are regarded as two sets of mathematical intervals,
   the transformed form of all combinations of the elements (the real
   values) represented by the prior set shall be a member of the
   posterior set.  A language may specify a mode and constraints on
   programs in which all implementations are required to deliver the
   same results, but is not required to.

I don't think that this is the right place to specify what reproducible
behaviour is, so the last sentence may need changing.

Regards,
Nick Maclaren.