for iterator hasNext does the current element count as a tru

Question

for iterator hasNext does the current element count as a true condition

ribesg · Answer

Read the doc

ribesg · Answer

`hasNext ` returning `true` means that `next ` will work

Smallville7123 · Answer

eg if there is only a single element

Smallville7123 · Answer

as `s forEach println it = $it ` does not print the last element if there is more than 1 element and does not print anything at all if there is only 1 element

gildor · Answer

What is s what is forEach where is an iterator

Smallville7123 · Answer

```fun main val word = ab println word = + word val s = stringToStack word println stringToStack = $s val i = s iterator while i hasNext println next = + i next s forEach println it = $it ```

ribesg · Answer

What s `stringToStack`

gildor · Answer

This code doesn t mean anything without context Is it your own iterator implementation I suppose

gildor · Answer

If so you just have a bug therr

gildor · Answer

Iterator is just an interface with convention how it should behave not a magic you of course can implement it with incorrect behavior but all stdlib iterators do not have this problem

Smallville7123 · Answer

```word = ab stringToStack = a b next = a it = a ```

gildor · Answer

What is that It s not even valid Kotlin syntax

Smallville7123 · Answer

```fun stringToStack str String Stack lt String gt val deq = Stack lt String gt var i = 0 while i lt str length deq addLast str i++ toString return deq ```

Smallville7123 · Answer

<https kotlinlang slack com archives C0922A726 p1555335165128800 thread ts=1555334820 123300 amp cid=C0922A726> is the output of the program

gildor · Answer

Do you understand that your comments without context just mean nothing for other people so there is no chance to help you using it only if one try to guess what does this code mean

Shawn A · Answer

gildor · Answer

Because you asked recently about implementation details of iterator I suppose you implement your own iterator and this iterator implementation is incorrect

Smallville7123 · Answer

ribesg · Answer

What is this

ribesg · Answer

Why don t you just use `LinkedList`

Smallville7123 · Answer

i dont know

Smallville7123 · Answer

Smallville7123 · Answer

so theres `main` `stringToStack` `Stack` and `LinkedList`

ribesg · Answer

What the hell are you doing

gildor · Answer

LinkedList is Java class as I remember Smallville tried to implement this for Native but I m not sure

gildor · Answer

So is your question why my custom iterator has a bug Did you even tried to debug it

Smallville7123 · Answer

the documentation for it literally just states `Returns true if the iteration has more elements `

Smallville7123 · Answer

Smallville7123 · Answer

and `Returns the next element in the iteration ` for <https kotlinlang org api latest jvm stdlib kotlin collections iterator next html>

ribesg · Answer

Yes That is what the documentation states So what s your point

Smallville7123 · Answer

how am i supposed to know that Returns true if the iteration has more elements actually means `hasNext ` returning `true` means that `next ` will work

ribesg · Answer

Smallville7123 · Answer

which implies the `next` element not the `current` element

ribesg · Answer

What do you think `next` means

ribesg · Answer

It s supposed to return the next element not the current one I mean it s written right there in the name

Smallville7123 · Answer

the next element after the current element

ribesg · Answer

Yes that s what next is supposed to return

ribesg · Answer

Your implementation of next returns the current value

Smallville7123 · Answer

so it should be this ``` Returns the next element in the iteration override fun next T node = node next if node = null return node value throw Exception No Such Element ``` thus return

Smallville7123 · Answer

```word = ab stringToStack = a b next = b it = b ``` for ```fun main val word = ab println word = + word val s = stringToStack word println stringToStack = $s val i = s iterator while i hasNext println next = + i next s forEach println it = $it ```

gildor · Answer

gt which implies the `next` element not the `current` element There is no such thing as current element in iterator there is only next or nothing

ribesg · Answer

Yeah I said that your implementation of `next` was wrong I never said it was the only thing wrong

Smallville7123 · Answer

so when i next is first called it will return the first element then the next element on subsequent calls

Smallville7123 · Answer

instead of the second element then the next on subsequent calls

gildor · Answer

Yes otherwise it would be impossible to get the first element of iterator

Smallville7123 · Answer

ok

Smallville7123 · Answer

so it is this ``` override fun hasNext Boolean = node = null override fun next T val var0 = node value node = node next return var0 ```

Smallville7123 · Answer

do kotlin iterators throw an exception if next is called when hasNext returns false or does that only happen in JVM

Smallville7123 · Answer

for example ``` if tokenList peek == null try tokenList pop catch e java util NoSuchElementException return null ```

Smallville7123 · Answer

with `tokenList` originally being of type `ArrayDeque`

ribesg · Answer

Read the doc

Smallville7123 · Answer

```Throws NoSuchElementException if this deque is empty```