[cfp-interest 3689] pow(x,1)

[Fred J. Tydeman]

I assume that pow(x,1) is exactly x  [but it is not listed in C23: F.10.4.5 pow functions]
scalbn(x,0) is exactly x [as per F.10.4.19 in C23]

So, scalbn(DBL_TRUE_MIN,0) is exactly DBL_TRUE_MIN
And, I assume, pow(DBL_TRUE_MIN,1) should be exactly DBL_TRUE_MIN

As per C23, 7.12.2#7, those are underflow [since they are subnormal]
But, as per IEEE-754, they are NOT underflow [since they are exact].

Now, C23 7.12.2#7 allows the implementation to not indicate those
"underflows".  It also allows the implementation to raise FE_UNDERFLOW
even though IEEE-754 would not raise FE_UNDERFLOW.

Do we need to add words to C2y about the difference on exact subnormal?

Should pow(x,1) being exactly x be added to Annex F?


---
Fred J. Tydeman        Tydeman Consulting
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