From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 24 Jan 2016 17:53:03 +0000 (-0500)
Subject: Yet further adjust degree-based trig functions for more portability.
X-Git-Tag: REL9_6_BETA1~822
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=00347575e2754b1aaacd357776560803564d3f35;p=postgresql

Yet further adjust degree-based trig functions for more portability.

Buildfarm member cockatiel is still saying that cosd(60) isn't 0.5.
What seems likely is that the subexpression (1.0 - cos(x)) isn't being
rounded to double width before more arithmetic is done on it, so force
that by storing it into a variable.
---

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 788c17033f..d4e5d55347 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -2000,7 +2000,9 @@ sind_0_to_30(double x)
 static double
 cosd_0_to_60(double x)
 {
-	return 1.0 - ((1.0 - cos(x * RADIANS_PER_DEGREE)) / one_minus_cos_60) / 2.0;
+	float8		one_minus_cos_x = 1.0 - cos(x * RADIANS_PER_DEGREE);
+
+	return 1.0 - (one_minus_cos_x / one_minus_cos_60) / 2.0;
 }