java - Union and Intersection of Recursively Enumerable sets -


i having hard time writing code theorem: if , b recursively enumerable sets, union b , intersection b. know re sets sets contain output of recursive functions , can enumerated such set subset of natural numbers.

for union b:

public static function<integer, integer> union(function<integer, integer> enuma, function<integer, integer> enumb){ ... } 

could give me tips on how go implementing this.