setDifference
fn
SetDifference!(less, R1, R2) setDifference(alias less = "a < b", R1, R2)(R1 r1, R2 r2)Ditto
SetDifference!(less, R1, R2) setDifference(alias less = "a < b", R1, R2)(R1 r1, R2 r2)Ditto