function value(obj::ExtendedUnivariateDifferentiableFunction, arg0::Derivative)
    return jcall(obj, "value", Derivative, (Derivative,), arg0)
end

function value(obj::UnivariateDifferentiableFunction, arg0::DerivativeStructure)
    return jcall(obj, "value", DerivativeStructure, (DerivativeStructure,), arg0)
end

function value(obj::UnivariateFunction, arg0::jdouble)
    return jcall(obj, "value", jdouble, (jdouble,), arg0)
end

