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Hello,

I've found situations where meld returns an incorrect 0, when applied on some undistributed sums, namely

(w_{a} x_{b} y_{c}-w_{c} x_{b} y_{a}) f^{a c}
(w_{a} x_{b} y_{c} z_{d}-w_{c} x_{b} y_{a} z_{d}) f^{a b c}
(w_{a} x_{b} y_{c} z_{d}-w_{c} x_{b} y_{a} z_{d}) f^{a b c d}

More precisely, the above 3 lines are the output corresponding to the following input:

{a,b,c,d,e#}::Indices(Lorentz,parent=ambient).

f^{a b}::TableauSymmetry(shape=(1,1),indices=(0,1)).
f^{a b c}::TableauSymmetry(shape=(2,1),indices=(0,1,2)).
f^{a b c d}::TableauSymmetry(shape=(2,2),indices=(0,1,2,3)).

fac:=f^{a c}.
fabc:=f^{a b c}.
fabcd:=f^{a b c d};

Dwy:=(w_{a} y_{c} - w_{c} y_{a}).
Dwxy:=(w_{a} x_{b} y_{c} - w_{c} x_{b} y_{a}).
Dwyz:=(w_{a} y_{c} z_{d} - w_{c} y_{a} z_{d}).
Dwxyz:=(w_{a} x_{b} y_{c} z_{d} - w_{c} x_{b} y_{a} z_{d}).

for f in [fac,fabc,fabcd]:
    for D in [Dwy,Dwxy,Dwyz,Dwxyz]:
        fD=f*D
        meld(fD)
        if fD==0:
            print(f*D)
        Df=D*f
        meld(Df)
        if Df==0:
            print(D*f)
asked in Bug reports by (200 points)
edited by

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