35concept problem =
requires(T& obj,
const T& const_obj) {
36 typename T::variable_type;
37 typename T::scalar_type;
40 requires requires(
typename T::variable_type& var,
41 const typename T::scalar_type& coeff) { var = var + coeff * var; };
44 requires T::allowed_evaluations.allows(evaluation_type{.diff_coeff =
true});
46 requires requires(
const typename T::scalar_type& time,
47 const typename T::variable_type& var, evaluation_type evaluations) {
48 obj.evaluate_on(time, var, evaluations);
52 const_obj.diff_coeff()