RedBlackTree: Iterators become invalid after removing an element.

[981377660LMT]

package main

import (
	"fmt"

	"github.com/emirpasic/gods/trees/redblacktree"
)

func main() {
	tree := redblacktree.NewWithIntComparator()
	tree.Put(1, struct{}{})
	tree.Put(2, struct{}{})
	tree.Put(3, struct{}{})
	it1 := tree.Iterator()
	it2 := tree.Iterator()
	it1.Next()
	it2.Next()
	it2.Next()
	fmt.Println(it1.Key()) // 1 
	tree.Remove(2)
	fmt.Println(it1.Key()) // 1 
	it1.Next()
	fmt.Println(it1.Key()) 
        //  need to be 3 here
        // panic: runtime error: invalid memory address or nil pointer dereference
}

I think that after removing an element, the iterators of the other elements need to be unaffected.

[amoyraku]

You can not remove elements while you are using a iterator. You will make the iterator become invalid, then any operation on the iterator will cause a problem.

[PapaCharlie]

FWIW, when you use an iterator over a collection in Java, the returned iterator supports deleting the most recently returned element. Might be an acceptable way to support deletion during iteration?
https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html#remove--