ENHANCE: Recode assertion to avoid recursion trap

This fixes #3140
gap-system · Jun 13, 2019 · 3f85d62 · 3f85d62
1 parent fe8ebae
commit 3f85d62
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Showing 2 changed files with 10 additions and 2 deletions.
diff --git a/lib/fitfree.gi b/lib/fitfree.gi
@@ -113,7 +113,7 @@ local ffs,hom,U,rest,ker,r,p,l,i,depths;
     for i in U{[1..Length(U)-1]} do # last one is length+1
       p:=PositionProperty(r,x->x>=i);
       if p<>fail and p<=Length(ipcgs) and not p in l then
-	Add(l,p);
+        Add(l,p);
       fi;
     od;
     Add(l,Length(ipcgs)+1);

diff --git a/lib/matrix.gi b/lib/matrix.gi
@@ -476,8 +476,16 @@ BindGlobal( "Matrix_CharacteristicPolynomialSameField",
             vec[i] := zero;
         fi;
     od;
-    Assert(3, IsZero(Value(cp,imat)));
     Assert(2, Length(CoefficientsOfUnivariatePolynomial(cp)) = n+1);
+    if AssertionLevel()>=3 then
+      # cannot use Value(cp,imat), as this uses characteristic polynomial
+      n:=Zero(imat);
+      one:=One(imat);
+      for i in Reversed(CoefficientsOfUnivariatePolynomial(cp)) do
+        n:=n*imat+(i*one);
+      od;
+      Assert(3,IsZero(n));
+    fi;
     Info(InfoMatrix,1,"Characteristic Polynomial returns ", cp);
     return cp;
 end );