is there any way to get current iteration using ge...

# announcements

[xii]

is there any way to get current iteration using generateSequence?

[xii]

so if you wanted the sequence to be (1, 2, 3, 4, 5) based on iteration value

[xii]

(i mean of course you can declare var 0 outside the generator and ++ it but im wondering if there is an idiomatic way)

[Guy Dupont]

I believe

generateSequence(0){it + 1}

will do it

[xii]

you're right for int, but what if you want to return something different?
lets say you want to use the current iteration as part of something else, like

generateSequence(0){
  if (fooCondition) "the number is ${it}"
  else null
}

[xii]

it wouldnt work, correct?

[Guy Dupont]

I think you would likely want to do that kind of logic in a block of code that consumes from the sequence, not from the sequence generation itself. So for the example you give you may want to append a .forEach or a .map

generateSequence(0){it + 1}
  .map { 
    if (fooCondition) "the number is ${it}"
  else null 
}

[Guy Dupont]

actually nevermind, that example with .map is functionally equivalent to yours. .forEach would actually cause the sequence to start iterating, and is likely what you want

[xii]

but that would generate an infinite sequence, no?

[Guy Dupont]

yes, unless you had a return statement

[xii]

i think my best shot is just using a normal counter as ugly as it is, because my use case is a bit more specific:

generateSequence(0){
  if (foo * it > bar) baz
  else null
}

[xii]

where baz is not an int of course

[Guy Dupont]

hmm interesting. Another suggestion to help avoid any nulls and the counter:

generateSequence(0) { it + 1 }
  .takeWhile { it * foo > bar }
  .map { baz }

[xii]

i love that one

[xii]

thank you!