generate all subsequences of a string

seqgen.go

package main

import "fmt"

type seqGen struct {
	baseStr string
	curI    int
	ch      chan string
}

func NewSeqGen(s string) chan string {
	sg := new(seqGen)
	sg.baseStr = s
	sg.ch = make(chan string)
	sg.curI = int(1<<uint(len(s))) - 1
	go sg.Start()
	return sg.ch
}

func (sg *seqGen) Start() {
	for sg.curI >= 0 {
		sg.ch <- maskString(sg.baseStr, sg.curI)
		sg.curI--
	}
	close(sg.ch)
}

func maskString(s string, mask int) string {
	var out string
	for i := uint(0); i < uint(len(s)); i++ {
		if mask&(1<<i) != 0 {
			out += s[i : i+1]
		}
	}
	return out
}

func main() {
	for s := range NewSeqGen("abc") {
		fmt.Printf("'%s'\n", s)
	}
}