text: import { iterate } from '@vect/vector-mapper'
  
  export const union = (a, b) => {
    const ve = a.slice()
    iterate(b, x => { if (!a.includes(x)) ve.push(x) })
    return ve
  }
  
  export const intersect = (a, b) => {
    const ve = []
    iterate(a, x => { if (b.includes(x)) ve.push(x) })
    return ve
  }
  
  export const difference = (a, b) => {
    const ve = []
    iterate(a, x => { if (!b.includes(x)) ve.push(x) })
    return ve
  }
  