func (s *Set) Add(items ...int32) {
	for _, item := range items {
		s.m[item] = keyExists
	}
}
Add includes the specified items (one or more) to the Set. The underlying
Set s is modified. If passed nothing it silently returns.
package i32set
import (
	"fmt"
	"strings"
)
var (
	keyExists   = struct{}{}
	nonExistent int32
)
const maxInt = int(^uint(0) >> 1)
type Set struct {
	m map[int32]struct{}
}
func New(ts ...int32) *Set {
	s := NewWithSize(len(ts))
	s.Add(ts...)
	return s
}
func NewWithSize(size int) *Set {
	return &Set{make(map[int32]struct{}, size)}
}