Opposite of intersect in groovy collections

Question

what would be the opposite of intersect in groovy collections?

Ceiling

This is very similar to This is very similar to #2544758 (but this question has a better title) – Encomium

Answer 1

You probably want to combine both the answers from @Andre and @denis

I think what you want is the union and then subtract the intersection from this

def a = [1,2,3,4,5]
def b = [2,3,4]

assert [1,5] == ( a + b ) - a.intersect( b )

The solution given by denis would depend on whether you do

def opposite = leftCollection-rightCollection // [1,5]

or

def opposite = rightCollection-leftCollection // []

which I don't think you wanted

Plato

Answer 2

I'm not certain what you mean by "opposite of union", but my guess is that you mean symmetric difference (AKA set difference or disjunction). The result of this operation is shown in red below.

The easiest way to perform this operation on two Java/Groovy collections is to use the disjunction method provided by Apache commons collections.

Fellow

Doesn't that just do ( a + b ) - a.intersect( b ) as I put in my answer? Worried my answer is incorrect now... – Plato

Yes, it does exactly the same as your answer, but I favour using the proven work of others over writing my own inferior untested implementation :) – You

No offence meant, I really mean my own crappy implementations, not yours :-) – You

The diagram was very helpful - thanks for taking the time to include it. – Holoblastic

Answer 3

Could it be this?

def leftCollection = [1,2,3,4,5]
def rightCollection = [2,3,4]
def opposite = leftCollection-rightCollection
println opposite

Prints

[1,5]

Federalize

In case, you use minus operator in Groovy, it might led to the weak of performance, according to link – Solve

Answer 4

use intersect for intersections

assert [4,5] == [1,2,3,4,5].intersect([4,5,6,7,8])

use + for unions:

assert [1,2,3,4,5] == [1,2,3] + [4,5]

see http://groovy.codehaus.org/groovy-jdk/java/util/Collection.html

Scraperboard

Answer 5

(a-b)+(b-a)
// (a-b) return [1,5]
//(b-a) return []
// TOTAL = [1,5]+[]

this is when we have: a=[1,2,3,4,5],b=[2,3,4,5]

OOP :

java.util.List.metaClass.oppIntersect={b->
  return ((delegate-b)+(b-delegate))
}

then

a.oppIntersect(b)

END!

Vitebsk