From da493b596e93dc98a4abf18bdc9f29c76ebb0a68 Mon Sep 17 00:00:00 2001
From: David Sanders <dpsanders@gmail.com>
Date: Tue, 25 Sep 2018 21:54:30 -0500
Subject: [PATCH] Fix (-3.. -2)^2

---
 src/intervals/functions.jl | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/intervals/functions.jl b/src/intervals/functions.jl
index d09bc2e00..6d2b51de3 100644
--- a/src/intervals/functions.jl
+++ b/src/intervals/functions.jl
@@ -204,14 +204,22 @@ function ^(x::Interval, n::Integer)  # fast integer power
         return inv(x^(-n))
     end
 
-    if iseven(n) && 0 ∈ x
+    if iseven(n)
+        if 0 ∈ x
 
-        return Interval(zero(eltype(x)),
+            return Interval(zero(eltype(x)),
                         power_by_squaring(mag(x), n, RoundUp))
 
-    #elseif x.lo > 0
+        elseif x.lo > 0
+            return Interval(power_by_squaring(x.lo, n, RoundUp),
+                            power_by_squaring(x.hi, n, RoundUp))
 
-    else
+        else  # x.lo < x.hi < 0
+            return Interval(power_by_squaring(-x.hi, n, RoundUp),
+                            power_by_squaring(-x.lo, n, RoundUp))
+        end
+
+    else  # odd n
 
          a = power_by_squaring(x.lo, n, RoundDown)
          b = power_by_squaring(x.hi, n, RoundUp)