fix: unary minus for sparse group algebra elems

thofma · Nov 19, 2024 · 4b6c2e6 · 4b6c2e6
1 parent 6eb76a2
commit 4b6c2e6
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/src/AlgAss/Elem.jl b/src/AlgAss/Elem.jl
@@ -147,8 +147,12 @@ end
 ################################################################################
 
 function -(a::AbstractAssociativeAlgebraElem{T}) where {T}
-  v = T[ -coefficients(a, copy = false)[i] for i = 1:dim(parent(a)) ]
-  return parent(a)(v)
+  if _is_sparse(a)
+    return parent(a)(-a.coeffs_sparse)
+  else
+    v = T[ -coefficients(a, copy = false)[i] for i = 1:dim(parent(a)) ]
+    return parent(a)(v)
+  end
 end
 
 ################################################################################

diff --git a/test/AlgAss/AlgGrp.jl b/test/AlgAss/AlgGrp.jl
@@ -107,6 +107,7 @@
       @test aa * bb == cc
       @test bb * aa == dd
       @test (aa + bb)^2 == QG(a)^2 + cc + dd + QG(b)^2
+      @test aa - bb == aa + (-bb)
     end
   end
 
@@ -129,6 +130,7 @@
       @test aa * bb == cc
       @test bb * aa == dd
       @test (aa + bb)^2 == QG(a)^2 + cc + dd + QG(b)^2
+      @test aa - bb == aa + (-bb)
     end
   end