[Cfp-interest 2970] islessgreater()

[Damian McGuckin]

This can be described as:

 	The islessgreater macro determines whether its first argument is
 	less than or greater than its second argument. The
 	islessgreater(x,y) macro is similar to (x) < (y) || (x) > (y) .

 	However, islessgreater(x,y) does not raise the "invalid"
 	floating-point exception when x and y are unordered and neither is
 	a signaling NaN (nor does it evaluate x and y twice).

What is the history here please?

While IEEE 754 had this operation as '<>' but it was signalling. There was 
no quiet version.

In 2002, Kahan referenced the same operation but again, it was signalling. 
He did have a quiet version defined with the operator as '!=?'. Is this 
its origin? It was in an Appendix in his March 23, 2002 paper:

 	Fclass: a Proposed Classification of Standard Floating-Point Operands

It had disappeared from IEEE 754 by IEEE 2008 and has not reappeared in 
IEEE 754 since.

Thanks - Damian