Fix degree computation for filtered rings (#923)

oscar-system · Dec 23, 2021 · 6183cb1 · 6183cb1
1 parent 4fa0067
commit 6183cb1
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Showing 2 changed files with 7 additions and 3 deletions.
diff --git a/src/Rings/mpoly-graded.jl b/src/Rings/mpoly-graded.jl
@@ -395,11 +395,11 @@ function degree(a::MPolyElem_dec)
     for i=1:length(c)
       u += c[i]*d[i]
     end
-    if isfiltered(W)
-      w = W.lt(w, u) ? u : w
-    elseif first
+    if first
       first = false
       w = u
+    elseif isfiltered(W)
+      w = W.lt(w, u) ? u : w
     else
       w == u || error("element not homogeneous")
     end

diff --git a/test/Rings/mpoly-graded-test.jl b/test/Rings/mpoly-graded-test.jl
@@ -185,6 +185,10 @@ end
 @testset "Degree" begin
   R, (x,y) = grade(PolynomialRing(QQ, ["x", "y"])[1]);
   @test_throws ArgumentError degree(zero(R))
+
+  Z = abelian_group(0)
+  R, (x,y) = filtrate(PolynomialRing(QQ, ["x", "y"])[1], [Z[1], Z[1]], (x,y) -> x[1] > y[1])
+  @test degree(x+y^3) == 1*Z[1]
 end
 
 @testset "Grading" begin