From e6356e0fd52a70936dc6f9ebfefbb54cc3970aac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lars=20G=C3=B6ttgens?= <lars.goettgens@rwth-aachen.de>
Date: Wed, 27 Sep 2023 17:36:36 +0200
Subject: [PATCH] Add `-(::SMat)`

---
 src/Sparse/Matrix.jl  | 6 +++++-
 test/Sparse/Matrix.jl | 3 +++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/Sparse/Matrix.jl b/src/Sparse/Matrix.jl
index c510ebaa63..9b6cb3743a 100644
--- a/src/Sparse/Matrix.jl
+++ b/src/Sparse/Matrix.jl
@@ -643,10 +643,14 @@ end
 
 ################################################################################
 #
-#  Addition
+#  Arithmetics
 #
 ################################################################################
 
+function -(A::SMat)
+  return map_entries(-, A)
+end
+
 function +(A::SMat{T}, B::SMat{T}) where T
   nrows(A) != nrows(B) && error("Matrices must have same number of rows")
   ncols(A) != ncols(B) && error("Matrices must have same number of columns")
diff --git a/test/Sparse/Matrix.jl b/test/Sparse/Matrix.jl
index a21589269c..54b6f192dc 100644
--- a/test/Sparse/Matrix.jl
+++ b/test/Sparse/Matrix.jl
@@ -171,6 +171,9 @@ using Hecke.SparseArrays
   DminusE = @inferred D - E
   @test DminusE == sparse_matrix(FlintZZ, [0 0 3; -1 1 -1; 0 1 0])
 
+  minusD = @inferred -D
+  @test minusD == sparse_matrix(FlintZZ, [-1 -5 -3; 0 -1 0; 0 -1 0])
+
   # Scalar multiplication
 
   D = sparse_matrix(FlintZZ, [1 5 3; 0 0 0; 0 1 0])