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Message-ID: <fb3a7daf-f478-1cb2-cc4-757d8b40bbfa@esi.com.au>
Date: Wed, 7 Aug 2024 00:02:59 +1000 (AEST)
From: Damian McGuckin <damianm@....com.au>
To: MUSL <musl@...ts.openwall.com>
Subject: Special cases in csinh and ctanh
Some special cases in ctanh.c are listed below:
/*
* ctanh(+-0 + i NAN) = +-0 + i NaN
* ctanh(+-0 +- i Inf) = +-0 + i NaN
* ctanh(x + i NAN) = NaN + i NaN
* ctanh(x +- i Inf) = NaN + i NaN
*/
if (!isfinite(y))
return CMPLX(x ? y - y : x, y - y);
What I thought are the same special cases in csinh.c are listed below:
They are processed differently in csinh than in ctanh.
/*
* sinh(+-0 +- I Inf) = sign(d(+-0, dNaN))0 + I dNaN.
* The sign of 0 in the result is unspecified. Choice = normally
* the same as dNaN. Raise the invalid floating-point exception.
*
* sinh(+-0 +- I NaN) = sign(d(+-0, NaN))0 + I d(NaN).
* The sign of 0 in the result is unspecified. Choice = normally
* the same as d(NaN).
*/
if ((ix | lx) == 0 && iy >= 0x7ff00000)
return CMPLX(copysign(0, x * (y - y)), y - y);
/*
* sinh(x +- I Inf) = dNaN + I dNaN.
* Raise the invalid floating-point exception for finite nonzero x.
*
* sinh(x + I NaN) = d(NaN) + I d(NaN).
* Optionally raises the invalid floating-point exception for finite
* nonzero x. Choice = don't raise (except for signaling NaNs).
*/
if (ix < 0x7ff00000 && iy >= 0x7ff00000)
return CMPLX(y - y, x * (y - y));
I realise that 'y - y' creates a NaN when y is either an Infinity or NaN.
Won't that also raise an INVALID exception?
What does
x * (y - y)
achieve that y - y does not (in the above)
Thanks - Damian
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