From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-committers(at)postgresql(dot)org |
Subject: | Re: pgsql: Tweak "line" test to avoid negative zeros on some platforms |
Date: | 2013-10-25 19:19:46 |
Message-ID: | 526AC452.9020501@gmx.net |
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Thread: | |
Lists: | pgsql-committers |
On 10/25/13, 10:55 AM, Tom Lane wrote:
> diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
> index 25f0bfd..41178a6 100644
> --- a/src/backend/utils/adt/geo_ops.c
> +++ b/src/backend/utils/adt/geo_ops.c
> @@ -1116,6 +1116,9 @@ line_construct_pts(LINE *line, Point *pt1, Point *pt2)
> line->A = (pt2->y - pt1->y) / (pt2->x - pt1->x);
> line->B = -1.0;
> line->C = pt1->y - line->A * pt1->x;
> + /* on some platforms, the preceding expression tends to produce -0 */
> + if (line->C == 0.0)
> + line->C = 0.0;
> #ifdef GEODEBUG
> printf("line_construct_pts- line is neither vertical nor horizontal (diffs x=%.*g, y=%.*g\n",
> DBL_DIG, (pt2->x - pt1->x), DBL_DIG, (pt2->y - pt1->y));
>
>
> While this is surely pretty ugly, I think it is less ugly and more robust
> than what you've done here. Comments?
Hehe, if that work's, then yes, it's better.
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