Is there any package that can simplify functional derivatives in path integrals? For instance the expression (integrate over, $x,y,z,u,v,r,s$):
$$\int\delta_{J_{A}^x}\delta_{J_{B}^x}\delta_{J_{B}^x}\int{J_{B}^y}\Delta^{yz}_B{J_{B}^z}\int{J_{B}^u}\Delta^{uv}_B{J_{B}^v}\int{J_{A}^r}\Delta^{rs}_A{J_{A}^s},$$ where $$\delta_{J_{A}^x}:= \frac{\delta}{\delta {J_{A}^x}}$$ and $$\Delta^{rs}_A:=\Delta_A(r-s).$$
FeynCalcin Rolf Mertig's answer. – Jens Mar 11 '14 at 14:12