func pivots(sets [][]int) []int {
lengths := make([]int, len(sets))
for i, set := range sets {
lengths[i] = len(set)
}
return set.Pivots(lengths...)
}
func main() {
// BEGIN OMIT
a := sort.IntSlice{2, 3, 5, 7, 11, 13} // primes
b := sort.IntSlice{0, 1, 2, 3, 5, 8, 13} // Fibonacci numbers
c := sort.IntSlice{1, 2, 5, 14, 42} // Catalan numbers
data := append(append(a, b...), c...)
pivots := set.Pivots(len(a), len(b), len(c))
size := set.Apply(set.Inter, data, pivots)
data = data[:size]
fmt.Println(data)
// END OMIT
}
func ExampleApply() {
sets := []sort.IntSlice{
{1, 3, 5, 7, 9}, // odds from 1
{3, 5, 7, 9, 11}, // odds from 3
{5, 10, 15, 20}, // 5-multiples
{2, 3, 5, 7, 11}, // primes
}
pivots := make([]int, len(sets))
var orig, data sort.IntSlice
// concatenate the sets together for use with the set package
for i, set := range sets {
pivots[i] = len(set)
orig = append(orig, set...)
}
// transform set sizes into pivots
pivots = set.Pivots(pivots...)
tasks := []struct {
name string
op set.Op
}{
{"union", set.Union},
{"inter", set.Inter},
{"sdiff", set.SymDiff},
}
for _, task := range tasks {
// make a copy of the original data (Apply rearranges the input)
data = append(data[:0], orig...)
size := set.Apply(task.op, data, pivots)
data = data[:size]
fmt.Printf("%s: %v\n", task.name, data)
}
// Output:
// union: [1 2 3 5 7 9 10 11 15 20]
// inter: [5]
// sdiff: [1 2 3 7 10 15 20]
}
func ExampleApply_diff() {
// a - b - c - d cannot be used with Apply (Diff is non-associative)
// a - (b + c + d) equivalent, using Apply (Union is associative)
sets := []sort.IntSlice{
{0, 2, 4, 6, 8, 10}, // positive evens
{0, 1, 2, 3, 5, 8}, // set of fibonacci numbers
{5, 10, 15}, // positive 5-multiples
{2, 3, 5, 7, 11, 13}, // primes
}
var data sort.IntSlice
// for use with (b + c + d)
exprsets := sets[1:]
pivots := make([]int, len(exprsets))
// concatenate the sets together for use with the set package
for i, set := range exprsets {
pivots[i] = len(set)
data = append(data, set...)
}
// transform set sizes into pivots
pivots = set.Pivots(pivots...)
// calculate x = (b + c + d)
size := set.Apply(set.Union, data, pivots)
// concatenate the result to the end of a
data = append(sets[0], data[:size]...)
// calculate a - x
size = set.Diff(data, len(sets[0]))
data = data[:size]
fmt.Println("diff:", data)
// Output:
// diff: [4 6]
}