Module Expi.Eval

class type ['a, 'r] semantics = ['a, 'r] Eval.T2(M).semantics
class type virtual ['a, 'r, 's] domain = ['a, 'r, 's] Eval.T2(M).domain
class type virtual ['a, 'r, 's] eff = ['a, 'r, 's] Eval.T2(M).eff
class virtual ['a, 'r, 's] t : object ... end

a virtual base class for all evaluators