X3J3/96-173 Page 1 of 1 Date: November 13, 1997 To: X3J3 From: /HPC Subject: Nature of Interval Arithmetic One burning question is how should interval arithmetic be added to the language, module/intrinsic, multi-part standard, etc. Paper 171 provided some reasons why interval arithmetic as a module is undesirable. It seems that some of the negative feelings about adding intervals as an intrinsic type stem from implementation costs. That is, f2k should not impose a large cost upon all conforming processors. We propose that a suitable compromise is: 1. Interval arithmetic be part of the base standard, and adds an intrinsic datatype. 2. A processor shall be free to provide 0 or more interval kinds. An intrinsic function (selected_interval_kind or equivalent) shall be provided, and users will be required to use it to determine if this facility is available on a given processor. Note that there will be restrictions, the interval kinds must match real kinds, and the lower bound kind and the upper bound kind will be the same kind. (straw vote on 1+2 : 6-7-4) 3. Like the IEEE functionality, it may be the case that some suitable subsets may be useful (e.g. basic arithmetic support, i/o, and library support). X3j3/96-173r1