TITLE: Precedence of set union, intersect, and difference?
QUESTION [13 upvotes]: Online, I have read contradicting opinions on whether intersect should take precedence over union (by analogy to logical and and or), or whether all set operators should have equal precedence.
Which way makes more sense and why?
And where does difference fit in?  (I'd say it should be equal precedence to intersect because A - B = A intersect B'.)

REPLY [12 votes]: There is no sensible way of preferring one of intersection and union more than the other, since complement switches them.  I don't think you should assume an order at all and you should always use parentheses.

REPLY [10 votes]: Since there are contradicting opinions, I recommend assuming that whoever is reading your work assumes a different precedence order than you do, and using lots of parentheses.