Re: [PATCH] sysdeps: Update Taylor Series formula in comment

[Paul Zimmermann <Paul.Zimmermann@inria.fr>]

       Dear Akila,

this change looks good to me.

To make the code clearer, what do you think of changing 'a' into 'x' in
the macro TAYLOR_SIN (and 'da' to 'dx')?

Paul Zimmermann

> From: Akila Welihinda <akilawelihinda@ucla.edu>
> Date: Sat, 11 Dec 2021 10:02:14 -0800
> Cc: Akila Welihinda <akilawelihinda@ucla.edu>
> 
> The macro TAYLOR_SIN adds the term `-0.5*da*a^2 + da` in hopes
> of regaining some precision as a function of da. However the
> comment says we add the term `-0.5*da*a^2 + 0.5*da` which is
> different. This fix just updates the comment to reflect the
> code.
> 
> Signed-off-by: Akila Welihinda <akilawelihinda@ucla.edu>
> ---
>  sysdeps/ieee754/dbl-64/s_sin.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/ieee754/dbl-64/s_sin.c b/sysdeps/ieee754/dbl-64/s_sin.c
> index 7d89e3dfc2..31e08e3a70 100644
> --- a/sysdeps/ieee754/dbl-64/s_sin.c
> +++ b/sysdeps/ieee754/dbl-64/s_sin.c
> @@ -53,7 +53,7 @@
>  /* The computed polynomial is a variation of the Taylor series expansion for
>     sin(a):
>  
> -   a - a^3/3! + a^5/5! - a^7/7! + a^9/9! + (1 - a^2) * da / 2
> +   a - a^3/3! + a^5/5! - a^7/7! + a^9/9! - da*a^2/2 + da
>  
>     The constants s1, s2, s3, etc. are pre-computed values of 1/3!, 1/5! and so
>     on.  The result is returned to LHS.  */
> -- 
> 2.30.1 (Apple Git-130)