[_a_a_a_]

Any def for 'difference and intersection of regexes' might actually mean?

I guess for regexes r1 and r2 this means the diff and intersect of their extensional sets, expressed intensionally as a regex. I guess. But nothing seems defined, including what ^ is, or > or whatever. It's not helpful

[d66]

  negation (~α): strings not matched by α
  difference (α - β): strings matched by α but not β
  intersection (α & β): strings matched by α and β
  exclusive-or (α ^ β): strings matched by α or β but not both
  inclusion (α > β): does α matches all strings β matches?
  equality (α = β): do α and β match exactly the same strings?