[newbie] Scalar field's eq. of motion (itensor)



Hi,
 
I want to calculate the free real scalar field's equation of motion (flat space-time), so I go like:
 
load("itensor")
imetric(g)
ishow(L:-g([-u,-v],[])*covdiff(S([],[]),u)*covdiff(S([],[]),v)-m^2*S([],[])^2)$
ishow( diff(L,S([],[])) - covdiff( diff(L, covdiff(S([],[]),l) ),l ) )$
 
Now the problem: covdiff is differentiating the metric. How can I avoid that?
 
Thanks
 
Victor
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