From e220f756e795b972b72d4e8b9d729d1d9b73d2e2 Mon Sep 17 00:00:00 2001
From: Antonis Geralis <43617260+planetis-m@users.noreply.github.com>
Date: Wed, 25 Nov 2020 11:15:34 +0200
Subject: [PATCH] fix for comparing infinities (#16122)

---
 lib/pure/math.nim | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/pure/math.nim b/lib/pure/math.nim
index af31a57851..ccd766f461 100644
--- a/lib/pure/math.nim
+++ b/lib/pure/math.nim
@@ -177,6 +177,17 @@ proc almostEqual*[T: SomeFloat](x, y: T; unitsInLastPlace: Natural = 4): bool {.
   runnableExamples:
     doAssert almostEqual(3.141592653589793, 3.1415926535897936)
     doAssert almostEqual(1.6777215e7'f32, 1.6777216e7'f32)
+    doAssert almostEqual(Inf, Inf)
+    doAssert almostEqual(-Inf, -Inf)
+    doAssert almostEqual(Inf, -Inf) == false
+    doAssert almostEqual(-Inf, Inf) == false
+    doAssert almostEqual(Inf, NaN) == false
+    doAssert almostEqual(NaN, NaN) == false
+
+  if x == y:
+    # short circuit exact equality -- needed to catch two infinities of
+    # the same sign. And perhaps speeds things up a bit sometimes.
+    return true
   let diff = abs(x - y)
   result = diff <= epsilon(T) * abs(x + y) * T(unitsInLastPlace) or
       diff < minimumPositiveValue(T)