derive method
The differentiation of Abs is Sgn
Implementation
//TODO No differentiation possible for x = 0
@override
Expression derive(String toVar) => Sgn(arg) * arg.derive(toVar);
The differentiation of Abs is Sgn
//TODO No differentiation possible for x = 0
@override
Expression derive(String toVar) => Sgn(arg) * arg.derive(toVar);