Questions about NCEG

[Paul Eggert]

O'Keefe makes several good points about IEEE floating point and ANSI C,
including:

|(1) If you stick to the letter of the IEEE 754 and IEEE 854 standards,
|    conversion of numeric literals from decimal to binary (or possibly,
|    in the case of 854, to internal decimal) is a *run* *time* operation,

No C compiler that I know of does this.  Does this mean that no C compiler can
claim conformance to both IEEE 754 and ANSI C?  I fear that if we ask either
standards committee for a ruling, they'll refer us to the other committee.

|(3) There are special numbers (+ and - infinity, -0, NaNs, Vax reserved
|    operands, &c) which have no standard syntax.

There are ways to say the IEEE numbers in ANSI C + IEEE 754:

	#define minus_0 (-0.0)
	#define infinity (1e300*1e300)
	#define NaN1 (infinity-infinity)
	#define minus_infinity (-infinity)
	#define minus_NaN1 (-NaN1)

This lets you say some things portably that you can't say with hex contants,
e.g. ``the NaN that you get when you subtract infinity from itself'',
which has a different hex value in different implementations of IEEE 754.
Unfortunately, many compilers (e.g. GCC) get this sort of thing wrong,
and these bugs are further arguments for hex floating constants.