摘要: In classical computability theory, a recursive counterexample to theorem shows that the latter does not hold when restricted computable objects. These counterexamples are highly useful in Reverse Mathematics program, where aim of is determine minimal axioms needed prove given ordinary mathematics. Indeed, often (help) establish 'reverse' implication typical equivalence between said and at hand. The aforementioned generally formulated language second-order arithmetic. this paper, we show readily modified provide similar implications higher-order For instance, analogue 'sequence' topological notion 'net', also known as 'Moore-Smith sequence'. Finally, our results on metric spaces suggest can only be reasonably studied weak systems via representations (aka codes)