A tour of Go #70

tour-of-go-70.go

package main

import "code.google.com/p/go-tour/tree"
import "fmt"

// Walk walks the tree t sending all values
// from the tree to the channel ch.
// FIXME: In this way how to close a channel when function returns the last value to terminate a loop
func Walk2(t *tree.Tree, ch chan int) {
    if t.Left != nil {
        Walk(t.Left, ch)
    }
    ch <- t.Value
    if t.Right != nil {
        Walk(t.Right, ch)
    }
}

// In-order
// To close a channel I can't call the function recursively...
func Walk(t *tree.Tree, ch chan int) {
    s := [](*tree.Tree){}
    for len(s) != 0 || t != nil {
        if t != nil {
          s = append(s, t)
          t = t.Left
        } else {
          t, s = s[len(s)-1], s[:len(s)-1]
          ch <- t.Value
          t = t.Right
        }
    }
    close(ch)
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
    fmt.Println("t1:", t1)
    fmt.Println("t2:", t2)
    ch1, ch2 := make(chan int), make(chan int)

    go func() {
        Walk(t1, ch1)
    }()
    go func() {
        Walk(t2, ch2)
    }()

    for {
      v1, ok1 := <-ch1
      v2, ok2 := <-ch2
      // detect Walking is finished
      if !ok1 || !ok2 {
        break
      }
      // compare v1, v2
      if v1 != v2 {
        return false
      }
    }

    // also returns true when t1 and t1 is empty
    return true
}

func main() {
    ch := make(chan int)
    t := tree.New(1)
    fmt.Println(t)
    go Walk(t, ch)
    for i := 0; i < 10; i++ {
        fmt.Println(<-ch)
    }
    fmt.Println(Same(&tree.Tree{}, &tree.Tree{}))
    fmt.Println(Same(tree.New(1), tree.New(1)))
    fmt.Println(Same(tree.New(1), tree.New(2)))
}