[Cfp-interest 2334] Re: nan("1111111111111111111111....")

[Jim Thomas]

> On Jan 16, 2022, at 10:30 AM, Fred J. Tydeman <tydeman at tybor.com> wrote:
> 
> F.10.8.2 The nan functions has:
> 2 The returned value is exact and is independent of the current rounding direction mode.
> 
> I read that as meaning no floating-point exceptions are raised by the nan() function.

That is the intention. It would have been better to say “The nan functions raise no floating-point exception.”

Note that F.10 #7 says

The "invalid" and "divide-by-zero" floating-point exceptions are raised as specified in subsequent subclauses of this annex.

and there is no specification for nan() to raise the “invalid” floating-point exception.

For implementation that don’t support Annex F, I believe the specification for floating-point exceptions is essentially what its implied by the specification for domain, range, and pole errors.

- Jim Thomas

> However, I have found that (at least) glibc raises FP_INVALID if the string passed
> to nan() has lots of valid characters.  Is that a bug in glibc?
> 
> 
> ---
> Fred J. Tydeman        Tydeman Consulting
> tydeman at tybor.com      Testing, numerics, programming
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