From 1b991905e57ea8357f1ec742bc511aeb6e33acfc Mon Sep 17 00:00:00 2001
From: Marcelo Forets <mforets@gmail.com>
Date: Sun, 30 Jun 2019 09:49:59 -0300
Subject: [PATCH] #1471 - No sorting for two-points convex hull (#1472)

* write non-sorting functions for two points convex hull

* remove code that sorts

* use ispermutation (needs 1439)

* fix test
---
 src/concrete_convex_hull.jl | 13 ++-----------
 test/unit_Zonotope.jl       |  2 +-
 test/unit_convex_hull.jl    |  5 ++---
 3 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/src/concrete_convex_hull.jl b/src/concrete_convex_hull.jl
index bef36e422b..9ebab74310 100644
--- a/src/concrete_convex_hull.jl
+++ b/src/concrete_convex_hull.jl
@@ -130,25 +130,16 @@ end
 
 function _two_points_1d!(points)
     p1, p2 = points[1], points[2]
-    if p1 == p2
-        # check for redundancy
+    if  _isapprox(p1[1], p2[1]) # check for redundancy
         pop!(points)
-    elseif p1[1] > p2[1]
-        points[1], points[2] = p2, p1
     end
     return points
 end
 
 function _two_points_2d!(points)
-    # special case, see #876
     p1, p2 = points[1], points[2]
-    if p1 == p2
-        # check for redundancy
+    if _isapprox(p1[1], p2[1]) && _isapprox(p1[2], p2[2]) # check for redundancy
         pop!(points)
-    elseif p1 <= p2
-        nothing
-    else
-        points[1], points[2] = p2, p1
     end
     return points
 end
diff --git a/test/unit_Zonotope.jl b/test/unit_Zonotope.jl
index 57cdfcb89a..48d6d5fb62 100644
--- a/test/unit_Zonotope.jl
+++ b/test/unit_Zonotope.jl
@@ -219,6 +219,6 @@ for N in [Float64]
         # constraints_list for generator matrix with a zero row
         Z = Zonotope(N[0, 0], N[2 3; 0 0])
         P = tovrep(HPolygon(constraints_list(Z)))
-        @test vertices_list(P) ≈ [N[5, 0], [-5, 0]]
+        @test ispermutation(vertices_list(P), [N[5, 0], [-5, 0]])
     end
 end
diff --git a/test/unit_convex_hull.jl b/test/unit_convex_hull.jl
index 98fa97220e..50d23b51cf 100644
--- a/test/unit_convex_hull.jl
+++ b/test/unit_convex_hull.jl
@@ -6,7 +6,7 @@ for N in [Float64, Rational{Int}]
     # corner cases in dimension 1
     @test convex_hull([Vector{N}(undef, 0)]) == [Vector{N}(undef, 0)]
     @test convex_hull([[N(0)]]) == [[N(0)]]
-    @test convex_hull([[N(2)], [N(1)]]) == [[N(1)], [N(2)]]
+    @test ispermutation(convex_hull([N[2], N[1]]), [N[2], N[1]])
     @test convex_hull([[N(2)], [N(2)]]) == [[N(2)]]
 
     # corner cases in dimension 2
@@ -18,8 +18,7 @@ for N in [Float64, Rational{Int}]
     p1 = [1., 2.]
     p2 = [1., 3.]
     @test convex_hull([p1]) == [p1]
-    @test convex_hull([p1, p2]) == [p1, p2]
-    @test convex_hull([p2, p1]) == [p1, p2]
+    @test ispermutation(convex_hull([p1, p2]), [p1, p2])
 
     # corner cases in higher dimension
     @test convex_hull([[N(0), N(0), N(0)]]) == [[N(0), N(0), N(0)]]