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Suppress -0 in the C field of lines computed by line_construct_pts().

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It's not entirely clear why some PPC machines are generating -0 here, since
the underlying computation should be exactly 0 - 0.  Perhaps there's some
wider-than-nominal-precision calculations happening?  Anyway, the best way
to avoid platform-dependent results seems to be to explicitly reset -0 to
regular zero.
This commit is contained in:
Tom Lane 2013-10-25 15:55:15 -04:00
parent 1f7a47912a
commit 43fe90f66a
1 changed files with 3 additions and 0 deletions
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3
src/backend/utils/adt/geo_ops.c
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@ -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));