Infinite streams in Scala

Question

Say I have a function, for example the old favourite

def factorial(n:Int) = (BigInt(1) /: (1 to n)) (_*_) 

Now I want to find the biggest value of n for which factorial(n) fits in a Long. I could do

(1 to 100) takeWhile (factorial(_) <= Long.MaxValue) last 

This works, but the 100 is an arbitrary large number; what I really want on the left hand side is an infinite stream that keeps generating higher numbers until the takeWhile condition is met.

I've come up with

val s = Stream.continually(1).zipWithIndex.map(p => p._1 + p._2) 

but is there a better way?

(I'm also aware I could get a solution recursively but that's not what I'm looking for.)

Answer 1

Stream.from(1) 

creates a stream starting from 1 and incrementing by 1. It's all in the API docs.