From d387ae6bd15d3450ff337f5ef6132709b1371b75 Mon Sep 17 00:00:00 2001
From: schillic <schillic@informatik.uni-freiburg.de>
Date: Tue, 11 Feb 2020 08:36:55 +0100
Subject: [PATCH 1/2] add 'similar' constructor

---
 src/matrix.jl    | 7 ++++++-
 test/runtests.jl | 8 ++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/matrix.jl b/src/matrix.jl
index 3ec49f39..36cd70dc 100644
--- a/src/matrix.jl
+++ b/src/matrix.jl
@@ -1,4 +1,4 @@
-import Base: split, ∈, ⊆
+import Base: similar, split, ∈, ⊆
 import Random: rand
 import IntervalArithmetic: inf, sup, mid, diam
 
@@ -90,6 +90,11 @@ function IntervalMatrix{T}(u::UndefInitializer, m::Integer, n::Integer=m) where
     return IntervalMatrix(mat)
 end
 
+# similar initializer
+function similar(M::IntervalMatrix)
+    return IntervalMatrix(similar(M.mat))
+end
+
 """
     IntervalMatrix(C::MT, S::MT) where {T, MT<:AbstractMatrix{T}}
 
diff --git a/test/runtests.jl b/test/runtests.jl
index c3c755ab..4ac5b8e2 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -11,6 +11,14 @@ using IntervalMatrices: _truncated_exponential_series, scale_and_square
     @test a * (b + 1) == -4.0..0.0
 end
 
+@testset "Interval matrix construction" begin
+    m1 = IntervalMatrix([-1.1..0.9 -4.1.. -3.9; 3.8..4.2 0.0..0.9])
+    m2 = IntervalMatrix{Float64}(undef, 2, 2)
+    @test m2 isa IntervalMatrix{Float64} && size(m2) == (2, 2)
+    m3 = similar(m1)
+    @test m3 isa IntervalMatrix{Float64} && size(m3) == size(m1)
+end
+
 @testset "Interval matrix arithmetic" begin
     a = 1.0..1.3; b = 2.0..3.5; c = -0.5 ± 0.5; d = 0.0 ± 0.1
     a₊ = 2.0..2.6; b₊ = 4.0..7.0; c₊ = -2.0..0.0; d₊ = -0.2..0.2

From 927ad7558417478f5e0447c20f57d375bce650ea Mon Sep 17 00:00:00 2001
From: schillic <schillic@informatik.uni-freiburg.de>
Date: Tue, 11 Feb 2020 08:39:50 +0100
Subject: [PATCH 2/2] use 'similar' constructor

---
 src/arithmetic.jl  | 4 ++--
 src/exponential.jl | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/arithmetic.jl b/src/arithmetic.jl
index 3a6c3401..702dbb8b 100644
--- a/src/arithmetic.jl
+++ b/src/arithmetic.jl
@@ -60,7 +60,7 @@ We follow [1, Section 6].
 matrix is NP-hard. SAC 2005.
 """
 function square(A::IntervalMatrix)
-    B = similar(A.mat)
+    B = similar(A)
     n = checksquare(A)
 
     # case i == j
@@ -83,5 +83,5 @@ function square(A::IntervalMatrix)
             end
         end
     end
-    return IntervalMatrix(B)
+    return B
 end
diff --git a/src/exponential.jl b/src/exponential.jl
index e4ff9e6e..9f487eef 100644
--- a/src/exponential.jl
+++ b/src/exponential.jl
@@ -30,7 +30,7 @@ function quadratic_expansion(A::IntervalMatrix{T}, t) where {T}
         end
     end
 
-    W = IntervalMatrix(similar(A.mat))
+    W = similar(A)
 
     @inbounds for j in 1:n
         for i in 1:n
@@ -95,7 +95,7 @@ bᵢⱼ = β\\sum_\\{k, k ≠ i, k ≠ j} a_{ik} a_{kj} + (α + βa_{ii} + βa_{
 matrix is NP-hard. SAC 2005.
 """
 function quadratic_expansion(A::IntervalMatrix, α::Real, β::Real)
-    B = similar(A.mat)
+    B = similar(A)
     n = checksquare(A)
 
     # case i = j
@@ -118,7 +118,7 @@ function quadratic_expansion(A::IntervalMatrix, α::Real, β::Real)
             end
         end
     end
-    return IntervalMatrix(B)
+    return B
 end
 
 function _truncated_exponential_series(A::IntervalMatrix{T}, t, p::Integer;